Obsessive-Compulsive Disorder (OCD) is a mental health disorder characterized by persistent, intrusive thoughts (obsessions) that cause distress or anxiety, and repetitive behaviors or mental acts (compulsions) that individuals feel driven to perform in response to the obsessions. These compulsions are aimed at reducing anxiety or preventing a dreaded event, but they are often excessive or unrealistic. OCD significantly interferes with daily life, impacting work, school, and relationships.
Obesity is a chronic disease characterized by excessive accumulation of body fat, usually resulting from a combination of genetic predisposition, lifestyle choices (diet and physical activity), and environmental factors. It's defined by a Body Mass Index (BMI) of 30 or higher and is associated with an increased risk of various health problems, including heart disease, type 2 diabetes, certain cancers, and osteoarthritis.
Obstructive Sleep Apnea (OSA) is a common sleep disorder characterized by repeated episodes of upper airway obstruction during sleep. These obstructions lead to pauses in breathing or shallow breaths, causing disruptions in sleep and reduced oxygen levels in the blood. OSA can significantly impact quality of life and increase the risk of various health problems.
Occupational asthma is a type of asthma caused or worsened by breathing in certain substances at work. It is characterized by airflow limitation and airway hyperresponsiveness attributable to workplace exposures. This exposure leads to sensitization and inflammation of the airways, resulting in asthma symptoms.
Ochronosis is a rare metabolic disorder characterized by the accumulation of homogentisic acid (HGA) in the body. This buildup leads to a dark pigmentation of connective tissues, particularly cartilage and skin, and can result in a variety of skeletal and extraskeletal manifestations. There are two main types: endogenous ochronosis, which is caused by a deficiency in the enzyme homogentisate 1,2-dioxygenase (HGD) due to a genetic mutation, and exogenous ochronosis, which is often associated with prolonged use of skin-lightening creams containing hydroquinone.
Ocular albinism (OA) is a genetic condition primarily affecting the eyes. It results from a reduced amount of melanin pigment in the iris and retina. This lack of pigment leads to visual problems, including reduced visual acuity, nystagmus (involuntary eye movements), and increased sensitivity to light. While individuals with OA typically have normal skin and hair pigmentation, some subtle changes can occur. OA is generally inherited in an X-linked recessive pattern, meaning it primarily affects males.
Ocular Histoplasmosis Syndrome (OHS) is an eye condition believed to be caused by a previous infection with the fungus
Histoplasma capsulatum
. The fungus is common in soil, particularly soil enriched with bird or bat droppings. While most people infected with
Histoplasma
have no symptoms or mild respiratory illness, in some individuals, it can lead to OHS years later. OHS doesn't involve active fungal infection in the eye; instead, it's thought to be an immune response to the prior infection that damages the retina. This damage can result in vision loss.
Oculocutaneous albinism (OCA) is a group of inherited genetic conditions characterized by a reduction or absence of melanin pigment in the skin, hair, and eyes. This lack of pigment leads to various visual problems and increased sensitivity to sunlight. OCA is not a disease that can be caught or spread. It is a genetic condition present from birth.
Oculopharyngeal Muscular Dystrophy (OPMD) is a rare genetic disorder characterized by progressive weakness of specific muscles, particularly those in the eyelids and throat (pharynx). This leads to difficulty swallowing (dysphagia) and drooping eyelids (ptosis). The severity and rate of progression vary significantly among affected individuals.
Odontomas are the most common type of odontogenic (tooth-related) tumor. They are benign (non-cancerous) growths composed of enamel, dentin, cementum, and pulp – the normal tissues of teeth – but arranged in a disorganized manner. They are generally slow-growing and usually asymptomatic until they interfere with tooth eruption. There are two main types: compound odontomas (resemble small, malformed teeth) and complex odontomas (an irregular mass of dental tissue).
Ogilvie's syndrome, also known as acute colonic pseudo-obstruction (ACPO), is a condition characterized by massive dilation of the colon in the absence of any mechanical obstruction. It's essentially a functional obstruction where the colon appears blocked, but there is no physical blockage present. It can be a serious condition, potentially leading to complications like bowel ischemia, perforation, and peritonitis if left untreated. It is most commonly seen in hospitalized or post-operative patients.
Oligodendroglioma is a type of brain tumor that arises from oligodendrocytes, cells in the brain and spinal cord that produce myelin, the protective sheath around nerve fibers. It is classified as a glioma, a tumor originating from glial cells. Oligodendrogliomas are typically slow-growing tumors and are often found in the cerebrum. They are graded based on their microscopic appearance, with lower-grade tumors generally having a better prognosis than higher-grade ones.
Oligomenorrhea refers to infrequent or light menstrual periods. It's defined as having menstrual cycles that occur more than 35 days apart, having fewer than nine periods per year, or having abnormally light flow. It's not a disease in itself but rather a symptom of an underlying issue. While occasional irregular periods are normal, persistent oligomenorrhea warrants medical evaluation.
Oligospermia is a male fertility issue characterized by a low sperm count in the semen. This means the number of sperm present in a single ejaculate is lower than the World Health Organization (WHO) standard. Low sperm count reduces the likelihood of fertilization, making it harder for a couple to conceive. It's often a result of various underlying medical conditions or lifestyle factors.
Olivopontocerebellar Atrophy (OPCA) refers to a group of neurodegenerative disorders characterized by the progressive deterioration of specific areas in the brain: the cerebellum, pons, and inferior olives. These areas are crucial for motor control, balance, and coordination. The resulting damage leads to a range of neurological symptoms that worsen over time. OPCA is not a single disease but rather a syndrome encompassing various underlying causes.
Ollier disease, also known as enchondromatosis, is a rare, non-hereditary skeletal disorder characterized by the development of multiple enchondromas (benign cartilaginous tumors) within the bones. These tumors typically arise in the metaphyses (the growing ends) of long bones, especially in the hands and feet, but can occur in other bones as well. Ollier disease can lead to bone deformities, limb length discrepancies, and an increased risk of bone fractures. There is also a significantly elevated risk of malignant transformation of the enchondromas to chondrosarcoma (a type of bone cancer).
Omenn Syndrome is a rare, severe form of severe combined immunodeficiency (SCID). It is characterized by immune dysregulation, leading to erythroderma (generalized red, scaling skin), hepatosplenomegaly (enlarged liver and spleen), lymphadenopathy (swollen lymph nodes), chronic diarrhea, failure to thrive, and recurrent infections. It is typically caused by specific mutations in genes involved in V(D)J recombination, a crucial process for immune system development.
Omphalitis is an infection of the umbilical stump and surrounding tissues in newborns. It's a serious condition that, if left untreated, can lead to severe complications like sepsis and necrotizing fasciitis. The infection occurs when bacteria enter through the cut umbilical cord after birth.
Omphalocele is a birth defect where the infant's intestines, liver, or other organs stick outside of the abdomen through the belly button. The organs are covered in a thin, transparent sac.
Onchocerciasis, also known as river blindness, is a parasitic disease caused by the filarial worm
Onchocerca volvulus
. It's transmitted to humans through the bite of infected blackflies (genus
Simulium
). The disease is endemic in parts of Africa, Latin America, and Yemen. It causes severe itching, skin disfigurement, and visual impairment, including blindness.
Ondine's Curse, also known as Congenital Central Hypoventilation Syndrome (CCHS), is a rare, lifelong condition affecting the autonomic nervous system. Primarily, it impairs the body's ability to control breathing, especially during sleep. Individuals with CCHS may require a tracheostomy and mechanical ventilation to survive. The severity varies, with some needing ventilation only during sleep while others need it 24/7. It is a genetic condition, typically diagnosed in infancy or early childhood.
Onychogryphosis, also known as ram's horn nails or claw nails, is a nail disorder characterized by thickening, increased curvature, and distortion of the nail, typically the toenails. The nail becomes overgrown, hard, and resembles a ram's horn or claw. It usually affects the great toenail, but can occur on other nails as well.
Onycholysis is the separation of the nail from the nail bed. This separation usually starts at the tip or sides of the nail and progresses towards the cuticle. The affected portion of the nail appears white or opaque due to the air space beneath it. It is usually painless, although the underlying cause might cause discomfort.
Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. It typically affects toenails more often than fingernails due to the slower growth and reduced blood supply in the feet. It causes changes in the nail's appearance, leading to thickening, discoloration, and potential separation from the nail bed.
Oophoritis is an inflammatory condition affecting one or both ovaries. It often occurs alongside salpingitis (inflammation of the fallopian tubes), in which case it is referred to as pelvic inflammatory disease (PID). Oophoritis can be acute (sudden onset) or chronic (long-term). It can lead to complications such as infertility, ectopic pregnancy, and chronic pelvic pain if left untreated.
Ophthalmoplegia refers to paralysis or weakness of one or more of the muscles that control eye movement. This can result in limited or absent eye movement in one or both eyes. It's not a disease itself, but rather a sign or symptom of various underlying conditions. Ophthalmoplegia can affect different directions of gaze and can be internal (affecting the pupil or focusing ability) or external (affecting the muscles that move the eye).
Opioid-Induced Hyperalgesia (OIH) is a paradoxical phenomenon where a person develops increased sensitivity to pain as a result of taking opioids. Instead of providing pain relief, opioids can, in some individuals, actually amplify pain or cause new pain to emerge. This is different from opioid tolerance, where the same dose of opioid becomes less effective over time. OIH involves an actual increase in pain sensitivity.
Opitz G/BBB syndrome is a rare genetic disorder characterized by a variety of physical abnormalities, particularly those affecting the midline structures of the body. This can include facial features, the larynx and trachea, the esophagus, and the genitourinary system. The severity of symptoms varies widely among affected individuals.
Opiate addiction, also known as opioid use disorder (OUD), is a chronic, relapsing disease characterized by compulsive drug seeking and use despite harmful consequences. It involves changes in the brain's reward system, leading to intense cravings and a loss of control over opiate use. Opiates include prescription painkillers (like oxycodone, hydrocodone, morphine) and illegal drugs (like heroin). Addiction can lead to significant physical, psychological, and social problems.
Opsoclonus Myoclonus Syndrome (OMS), also known as "dancing eyes-dancing feet" syndrome, is a rare neurological disorder characterized by rapid, involuntary, multi-directional eye movements (opsoclonus) and brief, shock-like muscle contractions (myoclonus). It often affects children, but can occur in adults. In children, it's frequently associated with neuroblastoma (a type of childhood cancer), while in adults, it can be linked to other cancers or have an unknown cause. The syndrome is believed to be autoimmune in nature, where the body's immune system mistakenly attacks the nervous system.
Optic atrophy refers to the degeneration of the optic nerve, which carries visual information from the eye to the brain. This degeneration leads to a reduction in the number of nerve fibers and can result in a decrease in vision, color perception, and visual field. Optic atrophy is not a specific disease but rather a sign of an underlying problem affecting the optic nerve. It can result from a variety of conditions, including inherited disorders, inflammation, tumors, trauma, and vascular problems.
Optic neuritis is an inflammation of the optic nerve, the bundle of nerve fibers that transmits visual information from your eye to your brain. This inflammation damages the optic nerve, which can cause pain and temporary vision problems. It's often associated with multiple sclerosis (MS), an autoimmune disease that affects the brain and spinal cord. However, it can also occur due to infections, other autoimmune diseases, or unknown causes.
Oral cancer encompasses cancers of the lips, tongue, gums, inner cheek lining, hard and soft palate, floor of the mouth, and the area behind the wisdom teeth. It's a serious condition that can be life-threatening if not diagnosed and treated early. Oral cancer is often associated with tobacco and alcohol use, but it can also occur in individuals with no known risk factors.
Oral candidiasis, also known as oral thrush, is a fungal infection caused by an overgrowth of the yeast
Candida albicans
in the mouth. While Candida is normally present in the mouth without causing harm, certain conditions can lead to its proliferation, resulting in the characteristic white, creamy lesions on the tongue, inner cheeks, gums, and sometimes the palate. It can affect people of all ages, but is more common in infants, elderly individuals, and those with weakened immune systems.
Oral herpes, also known as herpes labialis, is a common viral infection that causes sores around the mouth and lips. These sores are commonly called cold sores or fever blisters. It is caused by the herpes simplex virus type 1 (HSV-1). While there is no cure, treatment can help manage outbreaks and reduce their frequency.
Orbital cellulitis is an infection of the tissues around the eye. It's a serious condition that can cause pain, swelling, and vision problems. It typically affects the soft tissues of the orbit (the bony cavity surrounding the eyeball), but
does not
involve the eyeball itself. It's most common in children, but can occur in adults. If left untreated, it can lead to severe complications, including vision loss, brain infection, and even death.
Orchitis is an inflammation of one or both testicles, typically caused by a bacterial or viral infection. It can cause pain, swelling, and tenderness in the affected testicle. In some cases, orchitis can lead to infertility.
Organic acidemias (OAs) are a group of rare inherited metabolic disorders. They result from defects in specific enzymes or transport proteins that are needed to process certain amino acids, fats, and carbohydrates. These defects lead to a buildup of specific organic acids in the body, which can be toxic to the brain and other organs. Several specific types of OAs exist, including methylmalonic acidemia (MMA), propionic acidemia (PA), isovaleric acidemia (IVA), and others, each with a unique enzyme deficiency and characteristic organic acid accumulation.
Memory loss (short-term and long-term)
Confusion and disorientation
Impaired judgment
Difficulty with problem-solving and planning
Changes in personality or behavior (irritability, aggression, apathy)
Language difficulties (aphasia)
Visual-spatial difficulties
Mood disturbances (depression, anxiety)
Hallucinations or delusions (in some cases)
Decreased level of consciousness
Seizures
Ornithine Transcarbamylase Deficiency (OTCD) is a genetic disorder that prevents the body from properly processing nitrogen. Specifically, it affects the enzyme ornithine transcarbamylase, which is crucial for the urea cycle. The urea cycle removes ammonia, a toxic waste product, from the blood. When OTCD is present, ammonia builds up, leading to hyperammonemia, which can cause neurological damage and other serious health problems. It's the most common urea cycle disorder.
Orofacial clefts are birth defects that occur when the lip and/or mouth do not close completely during pregnancy. The two most common types are cleft lip (an opening in the upper lip) and cleft palate (an opening in the roof of the mouth). They can occur individually or together. Clefts can range in severity from a small notch in the lip to a complete separation of the lip and palate. These conditions can affect feeding, speech, hearing, and dental development. Treatment usually involves surgery, often followed by speech therapy and other specialized care.
Orotic aciduria is a rare autosomal recessive metabolic disorder characterized by the accumulation of orotic acid in the urine, blood, and tissues. This occurs due to a deficiency in the enzyme uridine monophosphate synthetase (UMPS), which is essential for the de novo synthesis of pyrimidines (building blocks of DNA and RNA). This deficiency disrupts normal cell growth and function, particularly in rapidly dividing cells like those in the bone marrow and gastrointestinal tract.
Orthostatic hypotension, also known as postural hypotension, is a form of low blood pressure that happens when you stand up from sitting or lying down. It can cause dizziness, lightheadedness, blurred vision, and even fainting. It occurs because gravity causes blood to pool in your legs when you stand. Normally, your body compensates for this by constricting blood vessels and increasing your heart rate, which helps maintain blood pressure. In people with orthostatic hypotension, this compensatory mechanism doesn't work properly.
Osgood-Schlatter disease is a common cause of knee pain in growing adolescents. It's an inflammation of the area just below the knee where the patellar tendon attaches to the tibial tuberosity (a bony bump on the shinbone). It usually develops during growth spurts, when bones, muscles, tendons, and other structures are changing rapidly. It's more common in boys, but the incidence is rising in girls, likely due to increased participation in sports.
Osler-Weber-Rendu syndrome, also known as hereditary hemorrhagic telangiectasia (HHT), is a genetic disorder that affects the blood vessels. It causes them to develop abnormally, making them prone to bleeding. This leads to the formation of telangiectasias (small, widened blood vessels) and arteriovenous malformations (AVMs; abnormal connections between arteries and veins) in various organs of the body, most commonly the nose, skin, lungs, brain, and liver.
Osmophobia is a heightened sensitivity or aversion to odors. It is not a disease in itself, but rather a symptom often associated with underlying medical conditions, particularly migraines and tension headaches. Individuals with osmophobia experience discomfort, nausea, or even headaches triggered by specific smells that are typically harmless or even pleasant to others.
Osteitis deformans, more commonly known as Paget's disease of bone, is a chronic disorder that disrupts the normal bone remodeling process. This process, where old bone is broken down and replaced with new bone, occurs too quickly in Paget's disease. The result is bone that is enlarged, weakened, and prone to fracture. It can affect one or more bones in the body. It is most common in older adults.
Osteitis Fibrosa Cystica (OFC), also known as brown tumor, is a skeletal disorder resulting from excessive parathyroid hormone (PTH), which typically occurs in hyperparathyroidism. The excess PTH causes bone resorption, leading to replacement of bone tissue with fibrous tissue and cysts. This weakens the bones and can cause pain, fractures, and deformities.
Osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of cartilage, the tissue that cushions the ends of bones within a joint. This breakdown leads to pain, stiffness, and reduced range of motion. OA is the most common type of arthritis and primarily affects weight-bearing joints such as the knees, hips, and spine, but can also affect other joints like hands and fingers.
Osteochondritis Dissecans (OCD) is a joint condition where a piece of bone and its cartilage separate from the end of the bone due to a lack of blood supply. This fragment can either remain partially attached or detach completely, becoming a loose body within the joint. OCD most commonly affects the knee, but can also occur in the elbow, ankle, or other joints. It typically occurs in adolescents and young adults.
Osteogenesis Imperfecta (OI), also known as brittle bone disease, is a genetic disorder characterized by bones that break easily, often from little or no apparent cause. The severity of OI varies greatly, ranging from mild cases with few fractures to severe forms that are lethal in infancy. Other common features can include short stature, hearing loss, blue sclerae (whites of the eyes), dental problems, and muscle weakness. There is no cure for OI, but treatments are available to manage the symptoms and improve quality of life.
Bone pain, especially in the hips, lower back, ribs, and legs.
Muscle weakness.
Difficulty walking.
Waddling gait.
Increased risk of fractures.
Muscle cramps.
Fatigue.
Osteomyelitis is an infection of the bone. It can occur when bacteria, fungi, or viruses invade a bone. Infections can reach a bone by traveling through the bloodstream or spreading from nearby tissue. In some cases, osteomyelitis can be caused by an open fracture or surgery. While once considered incurable, osteomyelitis can now be treated, though it can require lengthy courses of antibiotics.
Osteonecrosis, also known as avascular necrosis (AVN) or aseptic necrosis, is a condition that occurs when the blood supply to bone tissue is disrupted. This lack of blood flow leads to the death of bone tissue. Over time, this can cause the bone to collapse, leading to pain and limited joint movement. While it can affect any bone, it most commonly affects the hip, shoulder, knee, and ankle.
: Osteopenia is a condition where bone mineral density is lower than normal compared to healthy young adults, but not low enough to be classified as osteoporosis. It indicates a decrease in bone mass, making bones weaker and more susceptible to fractures. It is often considered a precursor to osteoporosis.
Osteopetrosis is a rare genetic disorder characterized by abnormally dense bones. This occurs because osteoclasts, the cells responsible for breaking down bone, do not function properly. While the bones become denser, they are also more brittle and prone to fracture. Osteopetrosis can manifest in various forms, ranging from mild, asymptomatic cases to severe, life-threatening conditions.
Back pain, which can be severe if there are fractured or collapsed vertebrae
Loss of height over time
A stooped posture
Bones that break more easily than expected
The ODI score should be interpreted in conjunction with the patient's clinical presentation.
It's one piece of information and shouldn't be used in isolation to make treatment decisions.
Changes in ODI scores over time can be useful for monitoring treatment effectiveness.
There are variations of the ODI, so use the validated version appropriate for the population.
Osteosarcoma is a type of bone cancer that originates in the cells that form bone. It is the most common type of bone cancer in children and adolescents, but it can also occur in adults. It most often affects the long bones of the arms and legs, particularly around the knee. Osteosarcoma is characterized by the production of immature bone (osteoid) by the cancerous cells. It is an aggressive cancer that can spread (metastasize) to other parts of the body, such as the lungs.
:
Children: Earaches are common in children, and prompt medical attention is important to prevent complications like hearing loss or speech delays.
Severe pain: Seek immediate medical attention for severe ear pain, especially if accompanied by fever, headache, stiff neck, or significant hearing loss.
Drainage: Ear drainage should always be evaluated by a doctor.
Underlying conditions: Identify and manage any underlying conditions that may be contributing to otalgia, such as TMJ disorders or sinus problems.
Prevention: Take preventive measures to reduce the risk of ear infections, such as avoiding smoking and managing allergies.
Otitis externa, commonly known as swimmer's ear, is an inflammation of the external ear canal. It is often caused by a bacterial or fungal infection and can be triggered by excessive moisture, injury, or allergies.
Otitis Media (OM) is an inflammation of the middle ear, usually caused by a bacterial or viral infection. It is a common condition, especially in children, and can occur as a result of a cold, flu, or allergy that causes the Eustachian tube (connecting the middle ear to the back of the throat) to become blocked. This blockage can lead to a buildup of fluid in the middle ear, creating an environment where bacteria or viruses can grow and cause infection.
Otosclerosis is a condition characterized by abnormal bone remodeling in the middle ear. This remodeling disrupts the stapes bone's ability to vibrate freely, which is essential for sound transmission. This leads to gradual hearing loss, often starting in one ear and then affecting both. The condition is more common in women and typically begins in early to mid-adulthood.
Ovarian cancer is a type of cancer that begins in the ovaries. The ovaries are female reproductive organs that produce eggs for reproduction and hormones like estrogen and progesterone. Ovarian cancer often goes undetected until it has spread within the pelvis and abdomen. At this late stage, ovarian cancer is more difficult to treat and is frequently fatal. Early-stage ovarian cancer, in which the disease is confined to the ovary, is more likely to be treated successfully.
Ovarian cysts are fluid-filled sacs that develop on an ovary. Many women develop at least one cyst during their lifetime. Most ovarian cysts are functional cysts, which form during the menstrual cycle and are not cancerous. They are often harmless and disappear on their own without treatment. However, some cysts can cause problems such as pain, bleeding, or, rarely, complications like rupture or torsion. Different types of cysts exist, some of which require medical attention.
Urgency: A sudden, compelling urge to urinate that's difficult to defer.
Frequency: Urinating eight or more times in a 24-hour period.
Nocturia: Waking up two or more times during the night to urinate.
Urge Incontinence: Involuntary leakage of urine that accompanies a strong urge to urinate.
: Overhydration, also known as water intoxication or hyponatremia, occurs when the body consumes more water than the kidneys can excrete, leading to an imbalance of electrolytes, particularly sodium. This dilution of sodium in the blood can cause cells to swell, leading to various health problems.
Pain (aching, burning, throbbing)
Stiffness
Tenderness
Weakness
Numbness
Tingling
Swelling
Reduced range of motion
Oxygen toxicity, also known as oxygen poisoning, is a condition resulting from breathing in excessive amounts of oxygen. While oxygen is essential for life, high concentrations or prolonged exposure can damage the lungs, central nervous system, and other organs. The severity of oxygen toxicity varies depending on the concentration and duration of exposure, as well as individual susceptibility. It is most commonly seen in premature infants receiving supplemental oxygen and in individuals undergoing hyperbaric oxygen therapy or mechanical ventilation.
Oxalosis, also known as primary hyperoxaluria (PH), is a rare, inherited metabolic disorder characterized by the overproduction of oxalate by the liver. This excess oxalate leads to the formation of calcium oxalate crystals that deposit in the kidneys and other organs, causing kidney damage, kidney stones, and eventually systemic oxalosis affecting the heart, bones, eyes, and other tissues. There are three main types of PH: PH1, PH2, and PH3, each caused by different gene mutations affecting different enzymes in the oxalate production pathway.
"Oasthouse Lung" is not a recognized or standard medical term. It's possible this is a colloquial or regional name for a respiratory illness, or a term specific to a particular environment or industry. Without more context, it is impossible to provide an accurate summary of the disease. Therefore, all subsequent sections will be based on general information about respiratory illnesses, as this is the closest possible interpretation. Assuming "Oasthouse Lung" is a respiratory illness, it could be a fungal infection, allergic reaction, or other type of lung inflammation potentially related to something found in an oasthouse environment.
Obesity hypoventilation syndrome (OHS) is a breathing disorder that affects some people with obesity. It's defined by the combination of obesity (usually a BMI of 30 kg/m² or higher), daytime alveolar hypoventilation (PaCO2 greater than 45 mmHg), and the absence of another known cause for hypoventilation. People with OHS often have other health problems, such as obstructive sleep apnea, high blood pressure, and heart failure. The primary issue is that the body doesn't breathe deeply or fast enough, leading to a buildup of carbon dioxide and a decrease in oxygen levels in the blood.
Oculomotor nerve palsy is a condition characterized by weakness or paralysis of the oculomotor nerve, which is the third cranial nerve. This nerve controls several eye movements, pupil constriction, and eyelid elevation. Damage to this nerve can result in a variety of eye movement abnormalities, including double vision (diplopia), a droopy eyelid (ptosis), and an abnormally dilated pupil.
Oculoauriculovertebral spectrum (OAVS), also known as Goldenhar syndrome, is a rare congenital disorder characterized by anomalies affecting the eyes (oculo-), ears (auriculo-), and spine (vertebral). The severity and combination of features vary widely among affected individuals. It is typically unilateral, affecting one side of the body more than the other, although bilateral involvement can occur.
Ogilvie Syndrome, also known as acute colonic pseudo-obstruction, is a condition characterized by massive dilation of the large intestine (colon) without any mechanical obstruction. It presents as a functional bowel obstruction, meaning there is no physical blockage, but the colon acts as if there were one. This dilation can lead to significant discomfort, complications like perforation (rupture) of the colon, and even death if not promptly treated.
Oligohydramnios is a condition in pregnancy characterized by a lower-than-normal amount of amniotic fluid surrounding the fetus. Amniotic fluid plays a crucial role in fetal development, allowing the baby to move freely, helping the lungs mature, maintaining a stable temperature, and protecting the baby from injury. Oligohydramnios can occur at any point in pregnancy but is most concerning during the third trimester. Its severity can range from mild to severe, and it may lead to various complications depending on the gestation week and the underlying cause.
Decreased urine output (less than 400 mL per day in adults)
Swelling in the legs, ankles, or feet (edema)
Dehydration
Fatigue
Confusion
Nausea
Shortness of breath (in severe cases due to fluid overload)
Onchocerciasis, also known as river blindness, is a parasitic disease caused by the filarial worm
Onchocerca volvulus
. It's transmitted to humans through the bites of infected blackflies (
Simulium
species). The disease primarily affects the skin and eyes, leading to intense itching, skin disfigurement, and visual impairment, including blindness. It is a major public health problem in parts of Africa, Latin America, and Yemen.
Nosebleeds (epistaxis)
Bleeding gums (gingival bleeding)
Blood blisters in the mouth (oral hemorrhagic bullae)
General weakness and fatigue
Skin hemorrhages (petechiae and ecchymoses)
Blood in the urine (hematuria) (Less common)
Bleeding in the eyes (subconjunctival hemorrhage) (Less common)
Bleeding into other organs (Less Common)
Oophoritis is an inflammatory condition affecting one or both ovaries. It often occurs alongside salpingitis (inflammation of the fallopian tubes), in which case the condition is termed salpingo-oophoritis or pelvic inflammatory disease (PID). Oophoritis can be acute or chronic and can lead to serious complications if left untreated.
Optic disc drusen (ODD) are deposits of hyaline material located within the optic disc, the area where the optic nerve enters the eye. They are often buried deep within the optic nerve and become more visible with age. While often asymptomatic, ODD can sometimes lead to visual field defects and, rarely, other complications. They are not a tumor or a growth.
Ophthalmoplegia refers to weakness or paralysis of one or more of the muscles that control eye movement. This can lead to limitations in the ability to move the eyes, double vision (diplopia), drooping eyelids (ptosis), and other related problems. It's not a disease itself but a sign of an underlying medical condition. Ophthalmoplegia can affect one eye (unilateral) or both eyes (bilateral), and it can develop suddenly or gradually.
Oral Allergy Syndrome (OAS), also known as pollen-food allergy syndrome, is a type of allergic reaction that occurs when individuals with pollen allergies experience localized allergic symptoms in the mouth after eating certain fresh fruits, vegetables, or nuts. The proteins in these foods are similar to those found in specific pollens, causing the immune system to react.
Oral lichen planus (OLP) is a chronic inflammatory condition that affects the mucous membranes inside your mouth. It appears as lacy, white patches; red, swollen tissues; or open sores. These lesions may cause burning, pain, or other discomfort. OLP isn't contagious. While most people can manage mild cases at home, more severe cases may require medical treatment. OLP increases the risk of oral cancer.
Orf, also known as contagious ecthyma or scabby mouth, is a viral skin disease primarily affecting sheep and goats. It is caused by the
Orf virus
, a parapoxvirus. While primarily an animal disease, Orf can be transmitted to humans through direct contact with infected animals or contaminated materials. In humans, it typically presents as a single, painful lesion, most often on the hands.
Orbital myositis is an inflammatory condition affecting one or more of the extraocular muscles (muscles that control eye movement) within the orbit (eye socket). It's characterized by inflammation and swelling of these muscles, leading to pain, restricted eye movement, and visual disturbances. Orbital myositis is relatively rare and can be either idiopathic (cause unknown) or associated with systemic inflammatory or autoimmune diseases.
Organic Solvent Neurotoxicity (OSN) refers to brain damage caused by exposure to organic solvents. These solvents are commonly found in paints, adhesives, cleaning agents, degreasers, and other industrial and household products. Prolonged or high-level exposure can damage the nervous system, leading to a range of neurological and psychological symptoms. The severity of OSN can vary from mild, reversible effects to severe, permanent disability.
Symptoms vary based on the route of exposure, dose, and specific organophosphate involved. Common symptoms include:
Muscarinic effects: Salivation, lacrimation (tearing), urination, defecation, gastrointestinal upset (cramps, vomiting, diarrhea), emesis (vomiting), miosis (pinpoint pupils), bradycardia (slow heart rate), bronchospasm (narrowing of airways), bronchorrhea (excessive mucus secretion in the lungs)
Nicotinic effects: Muscle weakness, fasciculations (muscle twitching), cramps, paralysis, tachycardia (rapid heart rate), hypertension (high blood pressure)
Central nervous system effects: Anxiety, confusion, ataxia (loss of coordination), seizures, coma, respiratory depression.
Intermediate Syndrome: Occurs 24-96 hours after exposure, with weakness of the neck, proximal limb, and respiratory muscles.
Oripavine is not a disease but rather a chemical compound, a thebaine derivative, that is a key starting material in the semi-synthesis of many opioid pharmaceuticals. Addiction to oripavine directly is highly unlikely as it is not typically used in its pure form. The concern lies in the potential for addiction to drugs synthesized from oripavine, such as buprenorphine, etorphine, or other potent opioids. If someone were to become addicted to a substance derived from oripavine, the addiction would manifest as an opioid use disorder, characterized by compulsive drug-seeking behavior, continued use despite negative consequences, and withdrawal symptoms upon cessation.
Ornithosis, also known as psittacosis or parrot fever, is an infectious disease caused by the bacterium
Chlamydia psittaci
. While often associated with birds, particularly parrots, cockatiels, and pigeons, it can also affect other bird species and, importantly, be transmitted to humans. In humans, ornithosis typically presents as a flu-like illness, but it can sometimes lead to more severe complications such as pneumonia.
An oroantral fistula (OAF) is an abnormal communication or opening between the oral cavity (mouth) and the maxillary sinus (a hollow space in the cheekbone). It can lead to various complications if left untreated, including chronic sinusitis and infection. It is typically created during or after a dental extraction.
Orofecal diseases, also known as fecal-oral diseases, are a group of infectious diseases where pathogens (bacteria, viruses, parasites) are transmitted when fecal matter contaminates food, water, or objects and is then ingested. These diseases are strongly linked to inadequate sanitation, poor hygiene practices, and unsafe food handling.
Oriental Sore, also known as cutaneous leishmaniasis, is a parasitic disease transmitted through the bite of infected female phlebotomine sandflies. It typically manifests as skin lesions, sores, or ulcers, primarily on exposed areas of the body like the face, arms, and legs. The disease is caused by various species of the
Leishmania
parasite.
Orthostatic Intolerance (OI) isn't a disease in itself, but rather a condition where the body struggles to regulate blood pressure and heart rate when transitioning from a lying or sitting position to standing. This can lead to various symptoms, primarily due to reduced blood flow to the brain. The common symptom is feeling lightheaded or dizzy upon standing.
Os Trigonum Syndrome is a condition that causes pain in the back of the ankle. It occurs when the os trigonum, an extra bone that some people have behind the talus (ankle bone), gets pinched or irritated, usually due to repetitive ankle movements, especially plantarflexion (pointing the toes). It's common in activities like ballet, soccer, and basketball.
Osler-Weber-Rendu disease, also known as hereditary hemorrhagic telangiectasia (HHT), is a genetic disorder that causes abnormal blood vessel formation. These abnormal vessels, called telangiectasias, are fragile and prone to bleeding, often in the nose, skin, mucous membranes, and organs like the lungs, brain, and liver. HHT can lead to various complications, including anemia, stroke, and pulmonary hypertension.
Osmotic Demyelination Syndrome (ODS), previously known as Central Pontine Myelinolysis (CPM), is a neurological condition characterized by damage to the myelin sheath (the protective covering) of nerve cells in the brainstem, particularly the pons. It's primarily caused by rapid correction of chronic hyponatremia (low sodium levels in the blood). While the pons is most commonly affected, other areas of the brain can also be involved, leading to the broader term ODS.
Osteitis pubis is an inflammatory condition affecting the pubic symphysis, the joint where the left and right pubic bones meet in the front of the pelvis. It's characterized by pain in the groin, lower abdomen, and inner thigh. While it can affect anyone, it's most commonly seen in athletes, particularly those involved in sports that involve repetitive running, kicking, or twisting motions. It's not an infection, but rather a result of stress, overuse, or trauma to the joint.
Osteochondroma is the most common type of benign (non-cancerous) bone tumor. It usually develops during childhood or adolescence, affecting the growing ends of long bones, such as those in the legs, arms, or ribs. It consists of an overgrowth of cartilage and bone near the growth plate. In most cases, it stops growing when skeletal maturity is reached.
Osteoid osteoma is a benign (non-cancerous) bone tumor. It is characterized by a small, well-defined nidus (the actual tumor) of osteoid tissue, typically less than 1.5 cm in diameter, surrounded by a zone of reactive bone. It most commonly affects long bones, particularly the femur and tibia, but can occur in any bone. The hallmark symptom is pain, often described as dull and aching, that is typically worse at night and relieved by NSAIDs (Non-Steroidal Anti-Inflammatory Drugs).
Osteolysis is the breakdown or destruction of bone tissue. It can occur in various parts of the body and can be caused by a variety of factors, including infection, inflammation, tumors, and metabolic disorders. It can also be a complication of joint replacement surgery. The severity and treatment depend on the underlying cause.
An osteoma is a benign (non-cancerous) bone tumor, usually slow-growing. It's most commonly found on the skull, often in the sinuses (especially the frontal and ethmoid sinuses) or on the outer surface of the bone. Osteomas are generally asymptomatic and discovered incidentally during imaging for other reasons. However, depending on their size and location, they can cause problems.
Osteomalacia is a condition characterized by softening of the bones due to impaired bone mineralization. This is most often due to insufficient vitamin D, calcium, or phosphate. In adults, osteomalacia leads to bone pain, muscle weakness, and an increased risk of fractures. It is analogous to rickets in children, but rickets affects growing bones while osteomalacia affects mature bone.
Pain or tenderness in the infected bone
Swelling, redness, and warmth around the affected area
Fever, sometimes with chills
Fatigue
Irritability (especially in children)
Difficulty using or bearing weight on the affected limb
Drainage of pus through the skin (in chronic cases)
Osteonecrosis, also known as avascular necrosis (AVN) or aseptic necrosis, is a condition that occurs when blood supply to a bone is disrupted, leading to bone tissue death. Over time, this can cause the bone to collapse. It most commonly affects the hip, shoulder, knee, and ankle.
Osteopenia typically has no noticeable symptoms. It is often diagnosed during a bone density test (DEXA scan) performed for other reasons or as part of a screening. In some cases, people might experience bone pain or fractures more easily than expected, but these are more common in osteoporosis.
Osteopoikilosis, also known as spotted bone disease, is a rare, benign skeletal condition characterized by multiple small, round or oval-shaped areas of increased bone density. These dense spots are typically found throughout the skeleton, particularly in the ends of long bones, the pelvis, and the bones of the hands and feet. It is often discovered incidentally during X-rays performed for other reasons. Osteopoikilosis is usually asymptomatic and does not require treatment.
Osteosarcoma is a type of bone cancer that originates in bone cells. It is most common in children and young adults, but can occur at any age. It typically affects the long bones of the arms and legs, near the ends of the bones. Osteosarcoma is an aggressive tumor that can spread to other parts of the body, particularly the lungs.
Otosclerosis is a condition characterized by abnormal bone remodeling in the middle ear, specifically affecting the stapes (stirrup) bone. This abnormal bone growth prevents the stapes from vibrating properly, which interferes with sound transmission to the inner ear, leading to hearing loss. The hearing loss is usually gradual and progressive.
Ovarian Hyperstimulation Syndrome (OHSS) is an exaggerated response to excess hormones, usually occurring in women undergoing fertility treatments such as in-vitro fertilization (IVF). It causes the ovaries to become swollen and leaky, leading to fluid accumulation in the abdomen. In severe cases, it can be life-threatening.
Ovarian torsion is a painful condition that occurs when an ovary twists on the ligaments that hold it in place. This twisting can cut off the blood supply to the ovary and fallopian tube. It's considered a surgical emergency because prolonged lack of blood flow can lead to tissue death (necrosis) and loss of the ovary.
Overdentures, while beneficial for many edentulous (toothless) individuals, can be associated with specific issues that are not infectious diseases but rather complications arising from the appliance itself. These can include:
Soft Tissue Irritation: Inflammation, ulceration, or hyperplasia (tissue overgrowth) of the gums, palate, or tongue due to denture pressure, poor fit, or hygiene.
Denture Stomatitis: Inflammation of the oral mucosa under the denture, often associated with Candida fungal infection.
Caries and Periodontal Disease in Abutment Teeth: Decay or gum disease affecting the remaining natural teeth supporting the overdenture if hygiene is inadequate.
Ridge Resorption: The bone that supports the denture continues to shrink over time, potentially leading to instability and poor fit.
Poor Nutrition: Discomfort while eating can lead to patients to make poor dietary choices, leading to nutritional deficiencies.
Overlap syndrome refers to a condition where a person exhibits symptoms and characteristics of two or more distinct autoimmune diseases. These diseases commonly involve connective tissues and may include systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), scleroderma, polymyositis/dermatomyositis, and Sjögren's syndrome. The exact combination of diseases varies between individuals, making diagnosis and treatment complex.
Overuse tendonitis, also known as tendinopathy, is a condition characterized by inflammation and irritation of a tendon, the thick fibrous cord that connects muscle to bone. It arises from repetitive motions or sustained strain on a particular tendon, leading to microscopic tears and subsequent inflammation. While the term implies inflammation ("-itis"), chronic overuse tendonitis often involves degeneration of the tendon tissue itself, a condition sometimes referred to as tendinosis. It commonly affects tendons in the shoulder, elbow (tennis elbow or golfer's elbow), wrist, knee (jumper's knee), and ankle (Achilles tendonitis).
Obstructive uropathy refers to a blockage in the urinary tract that prevents the normal flow of urine. This blockage can occur anywhere from the kidneys to the urethra and can be partial or complete, unilateral (affecting one kidney) or bilateral (affecting both kidneys). The obstruction leads to a backup of urine, potentially causing kidney damage, infection, and other complications.
Occipital neuralgia is a distinct type of headache that causes piercing, throbbing, or electric-shock-like pain in the upper neck, back of the head, or behind the ears. It is believed to be caused by irritation or injury to the occipital nerves, which run from the top of the spinal cord to the scalp. The pain can be intense and debilitating, often triggered by light touch, movement, or pressure in the affected area.
Oculo-auriculo-vertebral dysplasia (OAV), also known as Goldenhar syndrome, is a rare congenital disorder characterized by anomalies affecting the eyes (oculo-), ears (auriculo-), and spine (vertebral). The severity and combination of features vary widely from person to person. It's typically unilateral (affecting one side of the body), but can be bilateral in some cases. OAV is not typically inherited, and its exact cause is not fully understood.
Oculocerebrorenal syndrome, also known as Lowe syndrome, is a rare X-linked recessive disorder that primarily affects the eyes, brain, and kidneys. It is characterized by congenital cataracts, intellectual disability, and kidney problems (renal tubular dysfunction). Affected males are primarily affected, while females are typically carriers and may experience milder symptoms.
Oculopharyngeal muscular dystrophy (OPMD) is a rare genetic disorder characterized by progressive muscle weakness, particularly affecting the eyelids and throat. This leads to drooping eyelids (ptosis) and difficulty swallowing (dysphagia). The symptoms typically appear in adulthood, usually between the ages of 40 and 60. OPMD is a progressive condition, meaning the symptoms worsen over time.
An odontogenic keratocyst (OKC), also known as a keratocystic odontogenic tumor (KCOT), is a benign but locally aggressive cystic lesion that arises from the dental lamina or its remnants in the jaws. It is characterized by its unique epithelial lining and a high recurrence rate if not completely removed. While considered benign, its growth pattern and potential for recurrence necessitate careful management.
Oesophagitis is inflammation of the esophagus, the tube that carries food from your mouth to your stomach. This inflammation can damage the esophagus, causing pain, difficulty swallowing, and other complications. It can be caused by various factors, including stomach acid reflux, infections, medications, allergies, and certain medical conditions.
Ogilvie syndrome, also known as acute colonic pseudo-obstruction, is a condition characterized by massive dilation of the colon in the absence of any mechanical obstruction. It behaves like a bowel obstruction, but there is no physical blockage. This can lead to significant discomfort, potential complications such as perforation (rupture of the colon), and sepsis.
Oligodendroglioma is a type of brain tumor that arises from oligodendrocytes, cells in the brain and spinal cord that produce myelin, the protective sheath around nerve fibers. These tumors are typically slow-growing and most commonly occur in adults. They are classified as gliomas, which originate from glial cells (supportive cells) in the brain.
Oligospermia, also known as low sperm count, is a male fertility issue characterized by having fewer sperm than normal in a semen sample. It is a significant cause of male infertility, as a lower sperm count reduces the chances of fertilization.
Oliguria is defined as abnormally low urine output. In adults, this is generally considered to be less than 400 mL of urine in a 24-hour period. It's a symptom of an underlying medical condition rather than a disease itself, indicating a problem with kidney function, dehydration, or other issues affecting fluid balance. Oliguria can range in severity and can be a sign of acute kidney injury or other serious conditions.
Omenn syndrome is a rare, life-threatening inherited immune disorder characterized by immune dysregulation. It is a form of severe combined immunodeficiency (SCID) with features of autoimmunity. It results in a malfunctioning immune system that attacks the body's own tissues while being unable to fight off infections effectively.
Ollier disease, also known as enchondromatosis, is a rare, non-hereditary skeletal disorder characterized by the presence of multiple enchondromas (benign cartilage tumors) that develop within the bones, primarily in the limbs. These tumors can cause bone deformities, growth disturbances, and an increased risk of fractures and, in rare cases, malignant transformation to chondrosarcoma.
Omphalitis is an infection of the umbilical stump and surrounding tissues in newborns. It's characterized by inflammation, redness, swelling, and sometimes pus discharge at the base of the umbilical cord after it's been cut. If left untreated, omphalitis can lead to serious complications, including sepsis and even death. Early diagnosis and treatment with antibiotics are crucial.
Onyalai is a severe, often fatal, thrombocytopenic purpura (low platelet count leading to bleeding) endemic to Southern Africa, particularly Namibia, Angola, and Botswana. It is characterized by sudden onset bleeding, especially nosebleeds, bleeding gums, and bruising. It is linked to the consumption of contaminated food, specifically millet or sorghum contaminated with toxic metabolites produced by the fungus
Phoma sorghina
.
Oophoritis is an inflammatory condition affecting one or both ovaries. It often occurs alongside salpingitis (inflammation of the fallopian tubes) as part of pelvic inflammatory disease (PID). Oophoritis can be acute or chronic and may lead to complications affecting fertility and overall reproductive health if left untreated.
Ophthalmoplegia refers to weakness or paralysis of one or more of the muscles that control eye movement. This results in limited or absent eye movement, potentially affecting one or both eyes. The condition can stem from various underlying causes, ranging from nerve damage to muscular disorders, and can manifest in different forms depending on which muscles are affected. It can affect the ability to look in certain directions, leading to double vision (diplopia) and other visual disturbances.
Strong cravings for opiates
Inability to control opiate use (using more than intended or for longer periods)
Spending a significant amount of time obtaining, using, or recovering from opiate use
Neglecting responsibilities at work, school, or home due to opiate use
Continuing to use opiates despite knowing it is causing problems in relationships or other areas of life
Developing tolerance (needing more of the opiate to achieve the desired effect)
Experiencing withdrawal symptoms when opiate use is reduced or stopped
Using opiates in risky situations, such as driving
Social withdrawal
Changes in sleep patterns
Changes in appetite
Optic atrophy refers to the degeneration of the optic nerve, which carries visual information from the eye to the brain. This degeneration results in the loss of nerve fibers and can lead to varying degrees of vision loss, ranging from mild blurring to complete blindness. It's not a disease in itself but rather a sign of an underlying condition that damages the optic nerve.
1. Summary About Disease Oral leukoplakia is a condition characterized by the formation of white or grayish patches inside the mouth. These patches are typically flat or slightly raised and cannot be scraped off. While often benign, leukoplakia can sometimes be a precancerous condition, meaning it has the potential to develop into oral cancer. It is important to have any suspicious oral lesions evaluated by a healthcare professional.
Orbital apex syndrome (OAS) is a collection of signs and symptoms resulting from damage or compression to structures passing through the orbital apex, the posterior part of the bony socket of the eye. This area contains vital nerves and blood vessels, specifically cranial nerves II (optic nerve), III (oculomotor nerve), IV (trochlear nerve), V1 (ophthalmic branch of the trigeminal nerve), and VI (abducens nerve), as well as sympathetic fibers and the ophthalmic artery and vein. Damage to these structures leads to a combination of visual impairment and eye muscle weakness.
Orchitis is an inflammation of one or both testicles. It can be caused by a bacterial or viral infection. Bacterial orchitis is often associated with epididymitis (inflammation of the epididymis) and is then called epididymo-orchitis. Viral orchitis is most often caused by the mumps virus. Orchitis can cause pain, swelling, and, in some cases, infertility.
Organic acidemias (OAs) are a group of rare, inherited metabolic disorders. They occur when the body can't properly break down certain amino acids and fats. This breakdown process relies on specific enzymes, and in OAs, these enzymes are either deficient or don't function correctly. This leads to a buildup of organic acids and other toxic substances in the blood, urine, and tissues, causing various health problems. Each specific OA is caused by a defect in a different enzyme within these metabolic pathways.
Organophosphate poisoning is a toxic condition resulting from exposure to organophosphate (OP) chemicals. These chemicals are primarily used in insecticides, herbicides, and nerve agents. OP poisoning disrupts the normal function of the nervous system by inhibiting acetylcholinesterase (AChE), an enzyme that breaks down acetylcholine, a neurotransmitter. This leads to an accumulation of acetylcholine at nerve endings, causing overstimulation of the cholinergic receptors throughout the body. The severity of poisoning can range from mild symptoms to life-threatening conditions, depending on the level and duration of exposure.
Oriental sore, also known as cutaneous leishmaniasis, is a parasitic disease transmitted through the bite of infected female sandflies. It primarily affects the skin, causing lesions, ulcers, or sores. It's prevalent in tropical and subtropical regions around the world.
Ornithine transcarbamylase deficiency (OTCD) is a genetic disorder caused by a deficiency of the enzyme ornithine transcarbamylase. This enzyme is crucial for the urea cycle, a process that removes ammonia, a toxic waste product, from the body. Without sufficient OTCD, ammonia builds up in the blood, leading to hyperammonemia and potential brain damage. OTCD is the most common urea cycle disorder. It varies in severity, with some individuals experiencing symptoms shortly after birth (neonatal-onset) and others developing symptoms later in life (late-onset).
Orofacial clefts, including cleft lip and cleft palate, are birth defects that occur when the lip and/or palate do not close completely during pregnancy. A cleft lip is a split in the upper lip, while a cleft palate is an opening in the roof of the mouth. These defects can occur individually or together and vary in severity. They can impact feeding, speech, and hearing, and often require surgical repair and ongoing management.
Orotic aciduria is a rare, inherited metabolic disorder characterized by an excessive accumulation of orotic acid in the urine. This happens because of a deficiency in one or more enzymes involved in the de novo synthesis of pyrimidines (building blocks of DNA and RNA). The main consequences are impaired growth, anemia, and sometimes, neurological problems. It exists in two forms: Type I (deficiency in both orotate phosphoribosyltransferase and orotidylate decarboxylase) and Type II (deficiency only in orotidylate decarboxylase).
Orthostatic hypotension (also known as postural hypotension) is a form of low blood pressure that happens when you stand up from sitting or lying down. It can cause dizziness, lightheadedness, blurred vision, and even fainting. The condition occurs because gravity pulls blood down into the legs and abdomen when you stand up. Normally, the body compensates by increasing heart rate and constricting blood vessels to maintain blood pressure. In people with orthostatic hypotension, these compensatory mechanisms don't work properly, leading to a sudden drop in blood pressure.
Osler-Weber-Rendu syndrome, also known as hereditary hemorrhagic telangiectasia (HHT), is a genetic disorder that affects blood vessels. It causes them to develop abnormally, making them prone to bleeding. This leads to various problems, most commonly nosebleeds, but also affecting the skin, mucous membranes, and internal organs like the lungs, liver, and brain.
Ossification of the Posterior Longitudinal Ligament (OPLL) is a condition characterized by the abnormal hardening (ossification) of the posterior longitudinal ligament (PLL), a band of tissue that runs along the back of the vertebral bodies inside the spinal canal. This ossification can narrow the spinal canal and compress the spinal cord or nerve roots, leading to neurological symptoms.
Osteitis deformans, more commonly known as Paget's disease of bone, is a chronic disorder that disrupts the normal bone remodeling process. This process, where old bone tissue is broken down and replaced with new bone, becomes accelerated and disorganized. As a result, bones can become enlarged, deformed, and weakened. It most commonly affects the pelvis, skull, spine, and legs.
Osteochondritis dissecans (OCD) is a joint condition where a piece of cartilage and a thin layer of underlying bone separates from the end of a bone. This fragment can either partially detach, remaining connected, or completely detach and float freely inside the joint space, becoming a "loose body." OCD most commonly affects the knee, but it can also occur in other joints like the ankle, elbow, and hip. It primarily affects children and adolescents who are still growing.
Osteogenesis imperfecta (OI) is a group of genetic disorders characterized by fragile bones that break easily. It is also known as brittle bone disease. The severity of OI varies greatly, ranging from mild forms with few fractures to severe forms with multiple fractures, skeletal deformities, and other medical problems. OI affects the body's production of collagen, a protein that is essential for strong bones.
Osteomalacia is a condition that weakens bones, causing them to become soft and prone to fractures. It is primarily caused by a deficiency in vitamin D, calcium, or phosphate, which are essential for bone mineralization. In adults, osteomalacia is similar to rickets in children.
Osteomyelitis is an infection of the bone. It can occur when bacteria, fungi, or other germs spread to a bone, often through the bloodstream. It can also happen if an injury exposes the bone to germs. Children are more prone to osteomyelitis in the long bones of the arms and legs, while adults are more likely to get it in the vertebrae (bones of the spine), hips, or feet, especially if they have conditions like diabetes. The condition can be acute (short-term) or chronic (long-term).
Osteonecrosis, also known as avascular necrosis (AVN) or aseptic necrosis, is a condition that occurs when blood supply to bone is disrupted, leading to bone cell death (necrosis). Over time, this can cause the bone to collapse, leading to pain, limited range of motion, and eventually, arthritis. Osteonecrosis can affect any bone, but it most commonly affects the hip, shoulder, knee, and ankle.
Osteopenia is a condition characterized by lower-than-normal bone density. It's a precursor to osteoporosis, meaning the bones are weaker than normal but not yet fragile enough to break easily. It increases the risk of fractures, especially with age.
Bone fractures: Increased susceptibility to fractures.
Bone pain: Chronic pain related to abnormal bone structure.
Anemia: Reduced red blood cell production due to bone marrow crowding.
Vision and hearing problems: Compression of cranial nerves due to bone overgrowth.
Growth retardation: Impaired bone growth.
Enlarged liver and spleen (hepatosplenomegaly): Due to extramedullary hematopoiesis (blood cell production outside the bone marrow).
Recurrent infections: Due to immune system dysfunction.
Dental problems: Delayed tooth eruption, dental caries, and abnormal tooth shape.
Hydrocephalus: Accumulation of fluid in the brain.
Often, there are no symptoms in the early stages of bone loss. But once osteoporosis has weakened your bones, you may have:
Back pain, caused by a fractured or collapsed vertebra
Loss of height over time
A stooped posture
Bones that break much more easily than expected
1. Summary about disease: Osteosarcoma is a type of bone cancer that originates in the cells that form bone. It is most common in children and young adults, but it can occur at any age. It often develops in the bones around the knee, either in the lower end of the thighbone (femur) or the upper end of the shinbone (tibia). It can also occur in the upper arm bone (humerus). Osteosarcoma is an aggressive cancer that can spread to other parts of the body, especially the lungs.
Otic barotrauma, also known as ear barotrauma or barotitis media, is damage to the ear caused by pressure differences between the air pressure in the middle ear and the air pressure in the environment. This commonly occurs during changes in altitude or pressure, such as flying, scuba diving, or hyperbaric oxygen therapy. It's essentially an inability of the Eustachian tube to equalize pressure.
Otitis externa, commonly known as swimmer's ear, is an inflammation or infection of the outer ear canal, the tube between the eardrum and the outside of the head. It's frequently caused by bacteria or fungi. While often associated with swimming, any activity that leaves moisture in the ear canal can create a breeding ground for these organisms.
Otitis media is an infection of the middle ear, the space behind the eardrum that contains tiny vibrating bones. It's common in children but can affect adults too. The infection often results from a bacterial or viral infection affecting the middle ear.
Otosclerosis is a condition characterized by abnormal bone remodeling in the middle ear. This abnormal bone growth primarily affects the stapes, a small bone crucial for transmitting sound vibrations to the inner ear. As the stapes becomes fixed, sound transmission is impaired, leading to hearing loss. The hearing loss is usually gradual and progressive.
Ovarian cancer is a type of cancer that begins in the ovaries. The ovaries are female reproductive organs that produce eggs for reproduction, as well as the hormones estrogen and progesterone. Ovarian cancer often goes undetected until it has spread within the pelvis and abdomen. At this late stage, ovarian cancer is more difficult to treat and is frequently fatal. Early-stage ovarian cancer, in which the disease is confined to the ovaries, is more likely to be treated successfully.
Urgency: A sudden, strong urge to urinate that is difficult to defer.
Frequency: Urinating more than eight times in a 24-hour period.
Nocturia: Waking up two or more times during the night to urinate.
Urge incontinence: Involuntary loss of urine associated with a strong urge to urinate.
Ovarian cysts are fluid-filled sacs that develop on or within the ovaries. They are very common, and most women will develop at least one cyst during their lifetime. The majority of ovarian cysts are benign (non-cancerous) and cause no symptoms, resolving on their own within a few months. However, some cysts can cause pain, bleeding, or other complications, and may require medical treatment.
Symptoms of overhydration can range from mild to severe and may include:
Nausea and vomiting
Headache
Confusion and disorientation
Muscle weakness, spasms, or cramps
Seizures
Loss of consciousness
Swelling in hands, feet, and lips
Pain (aching, burning, throbbing)
Stiffness
Weakness
Tingling or numbness (paresthesia)
Swelling
Decreased range of motion
Tenderness to touch
Respiratory Issues: Coughing, shortness of breath, chest pain, lung irritation.
Neurological Problems: Headache, dizziness, seizures, stroke (rare but possible).
Cardiovascular Issues: Rapid heart rate, palpitations, embolism (if ozone is injected into the bloodstream).
Local Reactions: Pain, swelling, infection at the injection site.
Flu-like Symptoms: Fatigue, malaise, fever.
Eye Irritation: If ozone comes into contact with the eyes.
Gastrointestinal Issues: Nausea, vomiting (less common).
Hemolysis: Destruction of red blood cells (if ozone enters the bloodstream directly in high concentrations).
Oxycodone addiction is a chronic, relapsing brain disease characterized by compulsive seeking and use of oxycodone, a prescription opioid pain reliever, despite harmful consequences. It involves a complex interplay of factors, including brain changes, genetics, and environmental influences. Over time, tolerance develops, requiring higher doses to achieve the same effect. Dependence can also occur, leading to withdrawal symptoms upon cessation of use.
Obstetrical palsy, also known as brachial plexus birth palsy (BPBP), is a paralysis or weakness of the arm caused by injury to the brachial plexus nerves during childbirth. The brachial plexus is a network of nerves that originates in the neck and shoulder and controls movement and sensation in the arm, hand, and fingers. The severity of the injury can range from mild stretching to complete avulsion (tearing) of the nerves from the spinal cord.
An occipital encephalocele is a rare type of neural tube defect where a sac-like protrusion of the brain and meninges (the membranes covering the brain and spinal cord) occurs through an opening in the skull at the back of the head (occipital region). The severity can vary greatly depending on the size and contents of the sac. Some encephaloceles contain mainly cerebrospinal fluid and meninges, while others include brain tissue. This condition can cause a range of neurological problems, developmental delays, and physical deformities.
Ocular Graft-versus-Host Disease ( глаз GVHD) is a complication that can occur after hematopoietic stem cell transplantation (HSCT), also known as bone marrow transplant. In ocular GVHD, the donor's immune cells (the graft) recognize the recipient's tissues (the host), including the eyes, as foreign and attack them. This can lead to inflammation and damage to the ocular surface, tear glands, and other eye structures, causing a range of symptoms from mild dryness to severe vision impairment.
Oculocutaneous Melanosis (OCM), also known as Melanosis Oculi or Oculodermal Melanocytosis (nevus of Ota when the skin is involved), is a condition characterized by the presence of excessive pigmentation (melanin) in the eye and sometimes also the skin around the eye and forehead. It's a benign (non-cancerous) condition. The pigmentation often appears as a bluish-gray or brown discoloration. It is typically unilateral (affecting only one side of the face) but can rarely be bilateral (affecting both sides).
Odontodysplasia, also known as regional odontodysplasia (RO), is a rare, non-hereditary developmental abnormality affecting the hard tissues of teeth. It typically involves multiple teeth in a localized area of the mouth, often exhibiting a "ghost-like" radiographic appearance due to thin enamel and dentin. The affected teeth are malformed, poorly mineralized, and often fail to erupt or erupt incompletely.
Oesophageal achalasia is a rare disorder that makes it difficult for food and liquid to pass into the stomach. This occurs because the lower oesophageal sphincter (LES), a muscular ring that closes off the oesophagus from the stomach, fails to relax properly, and the oesophagus loses the ability to squeeze food down into the stomach (peristalsis).
1. Summary about disease: Oesophageal atresia (OA) is a rare birth defect where the oesophagus (the tube connecting the mouth to the stomach) doesn't develop properly. It usually ends in a pouch, preventing food from reaching the stomach. It often occurs with tracheoesophageal fistula (TEF), an abnormal connection between the oesophagus and the trachea (windpipe). This can allow stomach contents to enter the lungs.
Esophageal varices are enlarged veins in the lining of the esophagus, often caused by portal hypertension. Portal hypertension is usually a result of liver disease, most commonly cirrhosis. Varices are prone to rupture and bleeding, which can be life-threatening. Treatment aims to prevent bleeding and manage complications.
Ogilvie's syndrome, also known as acute colonic pseudo-obstruction (ACPO), is a condition characterized by massive dilation of the colon in the absence of any mechanical obstruction. It essentially mimics a bowel obstruction without there actually being a physical blockage. This dilation can lead to abdominal distension, pain, and, if left untreated, serious complications like bowel perforation. It's more common in hospitalized patients, particularly those who are critically ill or recovering from surgery.
Oligodendrogliomas are a type of primary brain tumor that arise from oligodendrocytes, the cells responsible for producing myelin, the protective sheath around nerve fibers in the brain and spinal cord. These tumors are typically slow-growing and classified as gliomas. They most commonly occur in adults, typically in the frontal and temporal lobes of the brain. Oligodendrogliomas are graded based on their aggressiveness, with Grade II being lower grade and Grade III (anaplastic oligodendroglioma) being higher grade.
Olivopontocerebellar Atrophy (OPCA) is a group of degenerative neurological disorders characterized by progressive atrophy (shrinkage) of the cerebellum (the part of the brain that controls coordination and balance), pons (part of the brainstem), and the olives (structures in the medulla oblongata involved in motor control). This leads to a gradual loss of motor control, balance, and other neurological functions. OPCA is not a single disease but rather a syndrome encompassing several distinct genetic and sporadic conditions with similar pathological features.
An omphalomesenteric duct remnant (also known as a vitelline duct remnant) is a congenital anomaly. During fetal development, the omphalomesenteric duct (also called the vitelline duct) connects the developing gut to the yolk sac, providing nourishment. Normally, this duct obliterates (disappears) between the 5th and 9th week of gestation. When this obliteration fails, various remnants can persist, including a Meckel's diverticulum (most common), omphalomesenteric cyst, omphalomesenteric sinus, or a fibrous band connecting the ileum to the umbilicus. These remnants can cause abdominal pain, bleeding, bowel obstruction, or infection.
Onchocerciasis, also known as river blindness, is a parasitic disease caused by the filarial worm
Onchocerca volvulus
. It is transmitted to humans through the bite of infected blackflies (
Simulium
species) that breed in fast-flowing rivers and streams. The disease is characterized by skin disease, including intense itching, disfiguring skin lesions, and visual impairment, including blindness. It is a major public health problem in parts of Africa, Latin America, and Yemen.
Onycho-osteodystrophy, also known as Nail-Patella Syndrome (NPS), is a rare genetic disorder that affects the development of nails, kneecaps (patellae), bones, and kidneys. The severity of symptoms varies widely among affected individuals, even within the same family. It is a systemic condition, impacting multiple body systems.
Ophryocystis elektroscirrha (OE) is a protozoan parasite that infects monarch and queen butterflies. It primarily affects the larval and pupal stages, but the effects are most visible in adult butterflies. Infected butterflies often have difficulty emerging from their chrysalis and may exhibit deformities. The parasite reduces flight ability, lifespan, and reproductive success.
Optic disc edema refers to swelling of the optic disc, which is the head of the optic nerve where it enters the eye. It is not a disease itself, but rather a sign of an underlying condition. The swelling can affect one or both eyes and can range from mild to severe. The condition requires prompt investigation to determine the cause and prevent potential vision loss.
Oral cavity cancer includes cancers of the lips, tongue, gums, lining of the cheeks, floor of the mouth, and hard palate. It is often classified as a type of head and neck cancer. Prognosis varies greatly depending on the stage at diagnosis.
Orbital apex syndrome (OAS) is a rare condition characterized by a constellation of neurological and ophthalmological deficits resulting from damage to structures passing through the orbital apex. The orbital apex is the posterior-most part of the bony orbit, containing the superior orbital fissure and optic canal. Structures traversing this area include cranial nerves II (optic), III (oculomotor), IV (trochlear), V1 (ophthalmic branch of the trigeminal), and VI (abducens), as well as sympathetic fibers and the superior ophthalmic vein. Damage to these structures can lead to a variety of symptoms, including vision loss, eye movement problems, facial sensory loss, and eyelid drooping.
Orchitis is an inflammation of one or both testicles. It can be caused by bacterial or viral infections. Bacterial orchitis is often associated with epididymitis (inflammation of the epididymis), and is then called epididymo-orchitis. Mumps is a common viral cause of orchitis, especially in unvaccinated males. Orchitis can cause pain, swelling, and, in some cases, infertility.
Memory loss (short-term and long-term)
Confusion
Impaired judgment
Difficulty with language (aphasia)
Difficulty with visual-spatial tasks
Personality changes
Irritability
Depression
Anxiety
Hallucinations or delusions (in some cases)
Disorientation (to time, place, or person)
Difficulty concentrating
Organophosphate (OP) poisoning is a serious condition that occurs when someone is exposed to organophosphate chemicals. These chemicals are primarily used in pesticides and insecticides. Exposure can disrupt the nervous system, leading to a range of symptoms from mild discomfort to severe, life-threatening complications. OPs inhibit acetylcholinesterase (AChE), an enzyme that breaks down the neurotransmitter acetylcholine. This leads to an accumulation of acetylcholine at nerve endings, causing overstimulation of the nervous system.
Orofaciodigital syndromes (OFDS) are a group of rare, genetically heterogeneous disorders characterized by malformations affecting the oral cavity, face, and digits. These syndromes involve a wide spectrum of features, and severity can vary significantly between individuals, even within the same type of OFDS. Several distinct types of OFDS have been identified, each with its own characteristic set of symptoms and genetic basis. These syndromes are typically caused by mutations in genes involved in cilia function and development.
Orthostatic intolerance (OI) is a condition in which an individual experiences symptoms when standing up from a lying down or seated position. These symptoms are caused by a reduced flow of blood to the brain due to the body's inability to properly regulate blood pressure upon standing. This can lead to a variety of uncomfortable and sometimes debilitating symptoms. OI is not a disease itself, but rather a syndrome, meaning it is a collection of symptoms that occur together. There are several types of OI, including Postural Orthostatic Tachycardia Syndrome (POTS), neurocardiogenic syncope (also known as vasovagal syncope or neurally mediated hypotension), and orthostatic hypotension.
Os Trigonum Syndrome is a condition that causes pain in the back of the ankle. It occurs when the os trigonum, an extra bone located behind the talus (ankle bone), is pinched between the talus and the calcaneus (heel bone). This pinching often happens during activities that require pointing the toes downwards (plantarflexion). The syndrome can result from a single injury or repetitive ankle movements.
Osteitis Condensans Ilii (OCI) is a benign (non-cancerous) condition affecting the iliac bones, which are part of the pelvis. It is characterized by bone sclerosis (increased bone density) along the sacroiliac (SI) joint, the joint where the sacrum (the triangular bone at the base of the spine) connects to the ilium. OCI is typically associated with repetitive stress or biomechanical factors affecting the SI joint.
Osteochondroma is the most common type of benign (non-cancerous) bone tumor. It typically develops during childhood or adolescence, affecting the growth plate (physis) near the ends of long bones like the femur (thigh bone), tibia (shin bone), and humerus (upper arm bone). It presents as an overgrowth of cartilage and bone near the end of a long bone.
Osteofibrous dysplasia (OFD), also known as Campanacci disease, is a rare, benign fibro-osseous lesion predominantly affecting the tibia and fibula of young children, typically under the age of 10. It's characterized by slow-growing, fusiform (spindle-shaped) thickening of the involved bones. Histologically, it features a mixture of fibrous tissue and immature bone. OFD is generally considered a benign condition, but its natural history is variable, and in some cases, it can be aggressive. The main challenge is differentiating OFD from adamantinoma, a rare bone cancer that can sometimes resemble OFD histologically.
Osteoid osteoma is a benign (non-cancerous) bone tumor that typically occurs in long bones, such as the femur and tibia, but can affect any bone in the body. It's characterized by a small, round, or oval lesion called a nidus, surrounded by reactive bone formation. While not life-threatening, osteoid osteomas can cause significant pain. It's most common in children and young adults.
Osteolysis is a process where bone tissue is destroyed and absorbed by the body. It can occur in various parts of the skeleton and may be caused by a range of factors, including inflammation, infection, tumors, or mechanical stress. The condition can lead to pain, instability, and functional impairment in the affected area.
1. Summary about disease: An osteoma is a benign (non-cancerous) bone tumor, typically slow-growing and often asymptomatic. It's characterized by the formation of new bone on existing bone, most commonly found on the skull, particularly the frontal and ethmoid sinuses. While generally harmless, an osteoma can cause problems if it grows large enough to obstruct sinuses, press on nerves, or cause cosmetic issues.
Osteomyelitis is an infection of the bone. It can occur due to bacteria, fungi, or viruses infecting the bone, most commonly bacteria. The infection can spread to the bone from nearby tissue, or it can travel through the bloodstream from other parts of the body. Osteomyelitis can affect people of all ages, but it's more common in children.
Osteonecrosis of the jaw (ONJ) is a rare but serious condition characterized by the progressive destruction and death (necrosis) of bone in the jaw. It often manifests as exposed bone in the mouth that does not heal. While it can occur spontaneously, it's most commonly associated with the use of bisphosphonates, a class of drugs used to treat osteoporosis and some cancers, and other antiresorptive or antiangiogenic medications. Dental procedures, such as tooth extractions, can trigger or exacerbate the condition.
Osteopetrosis is a rare genetic disorder characterized by abnormally dense bones. This occurs due to a defect in the function of osteoclasts, the cells responsible for bone resorption (breaking down bone tissue). The bones become abnormally hard and brittle, making them prone to fractures. It can present in varying degrees of severity, from mild forms discovered incidentally to severe, life-threatening forms presenting in infancy.
1. summary about disease Osteoporosis is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures, especially of the hip, spine, and wrist. It develops silently and progressively, often without any symptoms until a fracture occurs.
Nevus of Ota, also known as oculodermal melanocytosis, is a type of dermal melanocytosis (a skin condition characterized by the presence of melanocytes in the dermis). It typically presents as a blue-gray or brown hyperpigmentation on the face, most often around the eye and in the distribution of the first and second branches of the trigeminal nerve. It's a benign, acquired condition, though associated with a slightly increased risk of glaucoma and, rarely, melanoma.
Otitic hydrocephalus, also known as pseudotumor cerebri secondary to otitis media, is a rare condition characterized by increased intracranial pressure (pressure inside the skull) associated with ear infections (otitis media), particularly in children. Unlike true hydrocephalus, there's no obstruction of cerebrospinal fluid (CSF) flow, but the pressure is elevated, leading to symptoms mimicking a brain tumor.
Ovarian Hyperstimulation Syndrome (OHSS) is a potentially serious complication of fertility treatments that stimulate the ovaries to produce multiple eggs. It's characterized by enlarged ovaries and fluid shift from the bloodstream into the abdominal cavity. While mild forms are common and resolve on their own, severe OHSS can be life-threatening.
Ovarian torsion is a painful condition that occurs when an ovary twists around the ligaments that hold it in place. This twisting can cut off blood supply to the ovary and fallopian tube. If blood flow is cut off entirely, it can lead to tissue death (necrosis). It is a gynecological emergency that requires prompt diagnosis and treatment to preserve ovarian function.
Overhydration, also known as water intoxication or hyponatremia, occurs when the body takes in more fluid than the kidneys can remove. This leads to an imbalance in electrolytes, specifically a dilution of sodium in the blood. It can range from mild to life-threatening depending on the severity of the sodium imbalance.
Oxygen toxicity, also known as oxygen poisoning, is a condition resulting from breathing in excessive amounts of oxygen. This can damage the lungs and central nervous system. It typically occurs when breathing high concentrations of oxygen for extended periods. The severity depends on the oxygen concentration, duration of exposure, and individual susceptibility.
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