Trisomy 16

Trisomy 16 is a chromosomal abnormality in which there are three copies of chromosome 16 rather than two. It is the most common trisomy leading to miscarriage and the second most common chromosomal cause of it, closely following X-chromosome monosomy.

Causes

Trisomy 16 is usually caused by nondisjunction, a process in which cells divide improperly, resulting in an extra chromosome. This can occur in either the sperm or the egg that forms the fetus. The exact cause of nondisjunction is unknown, but it is believed that both genetic and environmental factors may play a role.

Symptoms

The symptoms of trisomy 16 vary depending on whether the individual has full or mosaic trisomy 16. Full trisomy 16, which means that every cell in the body has an extra chromosome 16, is not compatible with life and usually results in miscarriage in the first trimester. Mosaic trisomy 16, in which only some cells have an extra chromosome 16, can result in a range of symptoms including growth retardation, congenital heart defects, and developmental delays.

Diagnosis

Trisomy 16 can be diagnosed through several methods. Prenatal testing such as amniocentesis or chorionic villus sampling can detect the condition before birth. After birth, a karyotype test, which analyzes the number and structure of chromosomes in a cell, can confirm the diagnosis.

Treatment

There is no cure for trisomy 16. Treatment focuses on managing symptoms and may include physical therapy, special education, and surgeries to correct physical abnormalities.

Prognosis

The prognosis for individuals with mosaic trisomy 16 varies widely depending on the severity of symptoms. Some individuals may live relatively normal lives, while others may have severe disabilities.

See also

• Chromosome abnormality
• Genetic disorder
• Patau syndrome
• Edwards syndrome