Trisomy 8

Overview

Diagram of Chromosome 8

Trisomy 8, also known as Warkany syndrome 2, is a chromosomal disorder caused by the presence of an extra chromosome 8 in some or all of the body's cells. This condition is a type of aneuploidy, which refers to an abnormal number of chromosomes. Trisomy 8 can occur in a mosaic form, where some cells have the extra chromosome and others do not, or in a non-mosaic form, where all cells have the extra chromosome.

Clinical Features

Individuals with trisomy 8 may exhibit a variety of clinical features, which can vary widely in severity. Common characteristics include:

• Distinctive facial features such as deep-set eyes, prominent forehead, and broad nasal bridge.
• Musculoskeletal abnormalities, including joint contractures and scoliosis.
• Intellectual disability, which can range from mild to severe.
• Congenital heart defects.
• Renal anomalies.
• Gastrointestinal issues, such as Hirschsprung's disease.

Diagnosis

The diagnosis of trisomy 8 is typically made through karyotyping, a laboratory procedure that examines the number and structure of chromosomes in cells. In cases of mosaic trisomy 8, a skin biopsy may be performed to detect the presence of the extra chromosome in fibroblasts.

Genetic Mechanism

Trisomy 8 is usually the result of nondisjunction during meiosis, the process by which gametes (sperm and egg cells) are formed. This error leads to the production of gametes with an abnormal number of chromosomes. When such a gamete is involved in fertilization, the resulting zygote may have an extra chromosome 8.

Management

There is no cure for trisomy 8, and treatment is focused on managing the symptoms and complications associated with the condition. This may involve:

• Regular monitoring and treatment of heart defects.
• Physical therapy to address musculoskeletal issues.
• Special education services to support intellectual development.
• Surgical interventions for gastrointestinal or renal anomalies.

Prognosis

The prognosis for individuals with trisomy 8 varies depending on the severity of the symptoms and the presence of mosaicism. Those with mosaic trisomy 8 may have a milder phenotype and a better overall prognosis compared to those with non-mosaic trisomy 8.

Related Pages

• Chromosome 8
• Aneuploidy
• Karyotype
• Mosaicism