Chromosome 21, uniparental disomy of

Chromosome 21, Uniparental Disomy (UPD(21)) is a rare genetic condition characterized by an individual receiving two copies of chromosome 21 from one parent and none from the other. This article provides an overview of the condition, including its causes, symptoms, diagnosis, and potential treatments.

Causes

Uniparental disomy (UPD) occurs when a person inherits two copies of a chromosome from one parent, instead of one copy from each parent. UPD can arise through several mechanisms, including nondisjunction during meiosis, monosomy rescue, or post-zygotic mitotic errors. In the case of UPD(21), the individual has two copies of chromosome 21 from either the mother (maternal UPD(21)) or the father (paternal UPD(21)).

Symptoms

The symptoms of UPD(21) can vary widely among individuals and are often influenced by the presence of imprinting disorders or the unmasking of recessive genes. Some individuals may present with features similar to those of Down syndrome, although typically less severe, given that Down syndrome involves a full trisomy of chromosome 21. Other possible symptoms include developmental delays, intellectual disability, and characteristic facial features. However, it's important to note that some individuals with UPD(21) may exhibit minimal to no symptoms.

Diagnosis

Diagnosis of UPD(21) involves genetic testing and analysis, including karyotyping and molecular genetic testing. These tests can identify the presence of uniparental disomy and help distinguish UPD(21) from other chromosomal abnormalities. Prenatal diagnosis is also possible through procedures such as amniocentesis or chorionic villus sampling (CVS).

Treatment

There is no specific treatment for UPD(21), as management focuses on addressing the individual symptoms and conditions associated with the disorder. This may include early intervention programs, educational support, and therapies such as physical, occupational, and speech therapy. Regular monitoring and medical check-ups are recommended to manage and mitigate potential health issues.

Conclusion

Chromosome 21, Uniparental Disomy is a complex genetic condition with a wide range of potential symptoms and outcomes. Advances in genetic testing have improved the ability to diagnose UPD(21), allowing for better management and support for individuals with this condition.