Trisomy 13 Syndrome is a genetic disorder with onset before birth. It occurs approximately 1/5000 live births. Infants affected with Trisomy 13 tend to be small at birth. Spells of interrupted breathing in early infancy are frequent, and mental retardation is usually severe. Many affected children appear to be deaf. A moderately small head with sloping forehead, wide joints and openings between parietal bones of the head are present. Gross anatomic defects of the brain, especially failure of the forebrain to divide properly are common. A hernial protrusion of the cord and its meninges through a defect in the vertebral canal is found in almost 50% of cases.

The entire eye is usually small, and a defect of the iris tissue, and faulty development of the retina occur frequently. The supraorbital ridges are shallow and palapebral fissures are usually slanted. Cleft lip, cleft palate, or both are present in most cases. The ears are abnormally shaped and unusually low-set.

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Trisomy 13, also known as Patau Syndrome, is caused by a third copy of the thirteenth gene. It was first described in 1657, but four hundred fifty years of medical knowledge have not improved the outlook for children born with this syndrome. Most babies who are conceived with trisomy 13 die early in gestation. Of those who live to be born, about 44% die within the first month and 69% die by six months. The few who live past their first year have feeding problems, seizures, kidney problems, developmental delays, and spinal problems.

Problems present at birth may include some of the following:

Our farthest advances have been in early detection. Trisomy 13 is often detectable on ultrasound by 10 weeks. As early as 12 weeks, it can be seen in chorionic villus sampling. Amniocentesis, usually performed after 16 weeks gestation, can give a definite answer if any question still remains.

Often trisomy 13 is associated with older mothers. Even so, the risk of having another baby with trisomy 13 is usually very low -- unless the trisomy 13 is a translocation. A translocation is not associated with mom's age, but is a hereditary chromosome problem. The risk of recurrence in some types of translocations can be quite high. The inheritance of trisomy 13 is very complex. By testing the blood of both parents, a geneticist can give parents the best available information.


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