Summary about Disease
Fever of Unknown Origin (FUO) is defined as a fever of 101°F (38.3°C) or higher that lasts for at least three weeks, and the cause cannot be identified after initial investigations. It's not a specific disease but rather a category, a diagnostic challenge where the underlying reason for the persistent fever remains elusive despite medical evaluation. The fever can be constant, intermittent, or remittent.
Symptoms
The primary symptom is a persistent, unexplained fever of 101°F (38.3°C) or higher. Other symptoms can vary greatly depending on the underlying cause and may include:
Chills
Night sweats
Fatigue
Weight loss
Muscle aches (myalgia)
Joint pain (arthralgia)
Rash
Headache
Abdominal pain
Causes
FUO can be caused by a wide range of conditions. The most common categories of causes include:
Infections: Abscesses (hidden or deep-seated), endocarditis, tuberculosis, Lyme disease, HIV, and other atypical infections.
Neoplasms (Cancers): Lymphoma, leukemia, renal cell carcinoma, liver cancer, and other malignancies.
Autoimmune/Inflammatory Diseases: Systemic lupus erythematosus (SLE), rheumatoid arthritis, vasculitis (e.g., temporal arteritis), inflammatory bowel disease (IBD), and sarcoidosis.
Miscellaneous: Drug-induced fever, factitious fever (self-induced), pulmonary embolism, deep vein thrombosis, familial Mediterranean fever, and Still's disease.
Undiagnosed: In some cases, despite thorough investigation, the cause remains unknown.
Medicine Used
Treatment for FUO focuses on addressing the underlying cause. Therefore, the medications used vary greatly depending on the diagnosed condition. Examples include:
Antibiotics: For bacterial infections.
Antifungals: For fungal infections.
Antivirals: For viral infections.
Immunosuppressants: For autoimmune or inflammatory conditions (e.g., corticosteroids, methotrexate).
Chemotherapy or Radiation Therapy: For cancers.
NSAIDs or Acetaminophen: To manage fever and discomfort symptomatically, but these are not treatments for the underlying cause and should be used cautiously as they can mask the fever and hinder diagnosis. Note: Medications should only be prescribed and monitored by a qualified healthcare professional after diagnosis.
Is Communicable
Whether FUO is communicable depends entirely on the underlying cause. If the fever is due to a contagious infection (e.g., tuberculosis, influenza), then it is communicable. If the cause is non-infectious (e.g., cancer, autoimmune disease), then it is *not* communicable.
Precautions
Precautions depend on the potential underlying cause. General precautions include:
Hygiene: Frequent handwashing to prevent the spread of potential infections.
Avoiding Exposure: Avoiding close contact with individuals known to have contagious illnesses.
Proper Food Handling: Ensuring food is cooked and stored properly to prevent foodborne illnesses.
Vector Control: Taking measures to prevent insect bites (e.g., using insect repellent, wearing protective clothing) in areas where vector-borne diseases are prevalent.
Safe Sexual Practices: Practicing safe sex to prevent sexually transmitted infections.
Medical Adherence: Following the treatment plan prescribed by your doctor.
How long does an outbreak last?
Since FUO is a symptom and not a disease, an "outbreak" in the traditional sense isn't applicable. The duration of the fever itself depends on the underlying cause and how effectively it is treated. The fever will persist until the underlying cause is addressed. Some conditions might cause chronic, intermittent fevers over long periods if not properly managed.
How is it diagnosed?
Diagnosing FUO involves a comprehensive approach: 1. Detailed Medical History and Physical Examination: Gathering information about symptoms, travel history, exposures, medications, and family history. 2. Laboratory Tests:
Complete blood count (CBC)
Comprehensive metabolic panel (CMP)
Blood cultures (to detect bacterial infections)
Urine analysis and culture
Inflammatory markers (e.g., ESR, CRP)
Specific tests for suspected infections (e.g., HIV test, tuberculosis testing, Lyme disease testing)
Autoimmune antibody panels (e.g., ANA, rheumatoid factor) 3. Imaging Studies:
Chest X-ray
CT scans of the abdomen, pelvis, and chest
MRI scans
Echocardiogram (to assess heart valve infections)
Nuclear medicine scans (e.g., gallium scan, PET scan) 4. Biopsies:
Liver biopsy
Bone marrow biopsy
Temporal artery biopsy (if temporal arteritis is suspected) 5. Consultations with Specialists: Infectious disease, rheumatology, oncology. 6. Empiric Treatment: In some cases, a trial of antibiotics or other medications may be used to see if the fever responds, but this is generally avoided until a diagnosis is reasonably excluded to prevent masking the true cause.
Timeline of Symptoms
The timeline of symptoms varies significantly based on the underlying cause. There is no one typical timeline for FUO itself. It starts with a fever of at least 3 weeks of duration, but the progression of other symptoms and their timing relative to the fever onset depend on the specific disease process driving the fever. For example:
Infection: Fever might be the first symptom, followed by chills, body aches, and potentially specific symptoms related to the site of infection.
Autoimmune Disease: Fever might develop gradually along with fatigue, joint pain, and rash.
Cancer: Fever might be a later symptom, developing after other signs of cancer like weight loss, fatigue, or specific organ dysfunction.
Drug-induced fever: Fever typically begins days or weeks after starting a new medication.
Important Considerations
Travel History: Detailed travel history is crucial to rule out geographically specific infections.
Medication History: A thorough medication review is important to identify potential drug-induced fever.
Immunocompromised Status: Individuals with weakened immune systems (e.g., HIV, chemotherapy patients) are at higher risk for certain infections.
Age: Certain causes of FUO are more common in specific age groups (e.g., temporal arteritis in the elderly).
Persistence of Investigation: FUO diagnosis and treatment can be challenging. Persistence in seeking medical attention and thorough investigation are crucial. Repeat testing or referral to specialists are often necessary.
Patient Compliance: Following the doctor's instructions and adhering to the treatment plan are crucial for successful management.