Trisomy 13 Syndrome is a rare chromosomal disorder characterized by the presence of an extra chromosome 13. Characteristic features may include major developmental defects along the center of the brain and face (midline); cleft lip and cleft palate; extra fingers or toes (polydactyly) and other skeletal abnormalities; mental retardation; and/or congenital heart defects. Other symptoms may include deafness, visual impairment, cysts in the kidneys, and/or genital abnormalities. The symptoms and physical characteristics of Trisomy 13 Syndrome develop due to the presence of an additional chromosome 13 (complete trisomy). The exact cause of this disorder is not known.
National Organization for Rare Disorders, Inc.