Summary about Disease
Monosomy is a chromosomal abnormality where an individual is missing one chromosome from a pair. Instead of having the usual two chromosomes, they have only one. This can occur with any of the chromosomes, but some monosomies are more common (though still rare) and more survivable than others. The most well-known is Turner syndrome, which is monosomy X (females having only one X chromosome instead of two). Other monosomies are typically lethal before or shortly after birth.
Symptoms
Symptoms of monosomy vary greatly depending on which chromosome is missing. Common symptoms (particularly in survivable monosomies like Turner syndrome) can include:
Short stature
Delayed or absent puberty
Infertility
Heart defects
Learning disabilities
Skeletal abnormalities
Kidney problems
Lymphedema (swelling in the hands and feet)
Webbed neck
High blood pressure The severity and specific presentation of symptoms are highly individual.
Causes
Monosomy arises from an error during cell division, specifically during meiosis (the process of creating egg and sperm cells). This error, called nondisjunction, results in a gamete (egg or sperm) that either has an extra chromosome or is missing a chromosome. If a gamete missing a chromosome fertilizes a normal gamete, the resulting embryo will have monosomy. The risk of nondisjunction increases with maternal age for some chromosomal disorders, though it can occur in any pregnancy.
Medicine Used
There is no "cure" for monosomy, as it involves a genetic alteration. Treatment focuses on managing the symptoms and associated health problems.
Growth hormone: Often used in Turner syndrome to increase height.
Estrogen replacement therapy: Used in Turner syndrome to induce puberty and maintain secondary sexual characteristics.
Medications for heart defects: If present.
Medications for kidney problems: If present.
Supportive therapies: Speech therapy, physical therapy, occupational therapy, and educational support can be helpful.
Is Communicable
No, monosomy is not communicable. It is a genetic condition caused by a chromosomal abnormality and cannot be spread from person to person.
Precautions
There are no specific precautions to prevent monosomy in a general sense. Because it is a genetic error, it's not caused by environmental factors or behaviors. Genetic counseling may be beneficial for families with a history of chromosomal abnormalities or for women of advanced maternal age who are planning a pregnancy. Prenatal screening and diagnostic testing can detect some cases of monosomy during pregnancy.
How long does an outbreak last?
Monosomy is not an infectious disease and does not occur in outbreaks. The condition is present from conception and is lifelong.
How is it diagnosed?
Monosomy can be diagnosed prenatally or postnatally.
Prenatal diagnosis: Chorionic villus sampling (CVS) or amniocentesis can be performed to obtain fetal cells for chromosomal analysis (karyotyping). Non-invasive prenatal testing (NIPT) using maternal blood can screen for certain chromosomal abnormalities, but it requires confirmation with CVS or amniocentesis if a positive result is obtained.
Postnatal diagnosis: A blood sample is taken and the chromosomes are analyzed (karyotyped). A buccal swab can also be used for some genetic tests.
Timeline of Symptoms
The timeline of symptoms varies depending on the specific monosomy and its severity.
Prenatal: Some monosomies may be detected during prenatal ultrasound screening, with certain physical characteristics raising suspicion.
Infancy/Childhood: Symptoms like short stature, heart defects, or developmental delays may become apparent.
Adolescence: Delayed or absent puberty can be a significant symptom, particularly in Turner syndrome.
Adulthood: Infertility and other health problems may become more prominent. The progression of symptoms is often gradual and requires ongoing management.
Important Considerations
Genetic counseling: Crucial for families to understand the condition, recurrence risks, and available options.
Early intervention: Early diagnosis and intervention can significantly improve outcomes for individuals with monosomy.
Multidisciplinary care: Management often requires a team of specialists, including geneticists, endocrinologists, cardiologists, and other healthcare professionals.
Emotional support: Living with a genetic condition can be challenging, and emotional support from family, friends, and support groups is essential.
Research: Ongoing research continues to improve understanding and treatment of monosomy disorders.