Rare Genetic Disorders: Patau Syndrome

Patau syndrome, also known as Trisomy 13, is a chromosomal condition that occurs due to an extra chromosome. Patients with Patau syndrome suffer from severe intellectual disability and physical abnormalities.

1:16,000 newborns are born with Patau syndrome, however, due to the severe complications, the majority of them die shortly after birth. Only 5% of affected individuals live past their first year. Although the mother has a chance of having a child with Trisomy 13 at any age, the chances increase as the woman gets older.

Patau syndrome causes severe heart defects and brain and spinal cord abnormalities. The characteristic facial features include very small and poorly developed eyes (microphthalmia) as well as cleft lip. The patients are often born with extra fingers and toes. Furthermore, they suffer from weak muscle tone (hypotonia).

As previously stated, Trisomy 13 occurs due to an extra copy of the 13th chromosome. Thus, the affected individuals carry three copies of chromosome 13 instead of two in each of their cells. The extra genetic material disrupts healthy development, hence the severe health complications evolve. Some patients have milder symptoms of Patau syndrome because of the partial third chromosome. The part of the third chromosome is attached to a different chromosome, which is known as translocation and occurs during the development of the foetus.

The majority of the cases result from random events during the formation of sperm and eggs in the parents. These alterations occur due to the error in cell division known as nondisjunction. In rare cases, the syndrome can be inherited if one of the parents carries rearrangement of the genetic material (balanced translocation).