Trisomy 13

Alternative names:

Patau syndrome

Definition:

A syndrome associated with the presence of a third (extra) number 13 chromosome.

Causes, incidence, and risk factors:

Trisomy 13 (which occurs in about 1 out of every 20,000 live births) is seen at about half the rate of trisomy 18. It is a syndrome with multiple abnormalities, many of which are not compatible with more than a few months of life. Almost half of the affected infants do not survive beyond the first month and about three quarters die within six months.

Trisomy 13 is associated with multiple abnormalities, including severe mental defects and defects of the brain that lead to seizures (hypsarrhythmia), apnea, deafness and ocular abnormalities. The eyes are small with defects in the iris (coloboma). Most infants have a cleft lip and cleft palate and low-set ears. Congenital heart disease is present in approximately 80% of affected infants. Hernias and genital abnormalities are common.