Chromosome 15q, tetrasomy

Chromosome 15q tetrasomy is a rare chromosomal abnormality characterized by the presence of an extra copy of the long arm (q) of chromosome 15 in the cells of the body. This condition is also known as tetrasomy 15q or partial tetrasomy 15q, depending on whether the entire arm or just a part of it is duplicated. Chromosome abnormalities like 15q tetrasomy can lead to developmental delays, intellectual disabilities, and physical abnormalities.

Causes

The cause of chromosome 15q tetrasomy is typically a random event that occurs during the formation of reproductive cells (eggs and sperm) or in early fetal development. It is not usually inherited from the parents. The condition arises due to a process called nondisjunction, which results in an egg or sperm cell having an extra copy of chromosome 15q. When this cell contributes to the genetic makeup of a child, the child will have an extra chromosome 15q in each of their cells.

Symptoms

Symptoms of chromosome 15q tetrasomy can vary widely among individuals but may include:

• Intellectual disability
• Developmental delays
• Autism spectrum disorders
• Physical abnormalities such as facial dysmorphisms
• Low muscle tone (hypotonia)
• Heart defects
• Seizures

The severity of symptoms can vary, and not all individuals with tetrasomy 15q will have all these symptoms.

Diagnosis

Diagnosis of chromosome 15q tetrasomy is typically made through genetic testing, including karyotyping and fluorescence in situ hybridization (FISH), which can identify the extra chromosome material. More recently, array comparative genomic hybridization (aCGH) has been used to detect the condition, as it can provide more detailed information about the genetic material that is present.

Treatment

There is no cure for chromosome 15q tetrasomy, and treatment is symptomatic and supportive. This may include:

• Early intervention programs to address developmental delays
• Special education services
• Physical therapy
• Speech therapy
• Occupational therapy
• Management of any medical issues, such as heart defects or seizures

Prognosis

The prognosis for individuals with chromosome 15q tetrasomy varies depending on the extent of the duplication and the presence and severity of symptoms. With appropriate support, many individuals with this condition can lead fulfilling lives.

See also

• Chromosome 15
• Genetic disorder
• Nondisjunction