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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