A genetic disorder dominated by learning disability, ataxia, jerky puppet-like movements, epilepsy, and various behaviour problems, including some autistic features; associated with loss of maternal alleles on chromosome 15q11-13 and other genetic abnormalities (see figure below). Some 75% of those with the syndrome have a similar defect as found in the Prader-Willi syndrome, but occurring on chromosome 15. First reported by Harry Angelman (1915-1996) in 1965 in a study of three cases.