Syndrome, Prader-Willi

A condition characterized by muscle floppiness (hypotonia), excess appetite that if unchecked leads to obesity, small hands and feet and mental retardation. The syndrome is due to the lack in the child of chromosome region 15q11-13 from their father. The child may have two copies of chromosome region 15q11-13 from their mother (a phenomenon called maternal disomy). Although candidate genes in 15q11-13 have been identified, the exact gene or genes that give rise to the syndrome are not known. There is currently no specific treatment or cure for Prader-Willi syndrome. Parents are advised to limit consumption of high-calorie foods, and to use techniques such as special education, speech therapy, and physical therapy to maximize the child’s potential. In some cases, antidepressant or stimulant medication is tried, which may effect appetite, attention, and behavior. Severe psychiatric illness is common in Prader-Willi adults. Those with psychotic illness have a double maternal copy of 15q11-13, suggesting that genes in this region are important in causing psychotic illness.