The diagnostic features of 36 cases of Angelman's “happy puppet” syndrome are reported from the Hospital for Sick Children, Great Ormond Street, London. These include ataxia, developmental delay, paroxysmal laughter, seizures, and microcephaly. The facial appearance is characterized by a prominent jaw, wide mouth, and pointed chin. The ataxia of gait is associated with jerky limb movements and hand flapping. Muscle tone is variable, deep tendon reflexes normal, and plantar responses flexor. This series included 3 sibships of 3 affected sisters, 2 affected brothers, and 2 affected sisters, respectively. Males and females were equally affected. The electroencephalogram was abnormal in all cases and showed rhythmic slow waves at 4-6HZ and runs of 2-3 HZ anteriorly. On closure of eyes, spikes and 2-4 HZ slow waves occurred posteriorly. CT showed mild cerebral atrophy in 8 of 23 patients tested. Chromosome deletions of 15qll-13 were detected in 5 patients. 
COMMENT. Prior to this report, approximately 50 cases of Angelman's syndrome had been described in a period of 20 years. First considered to be sporadic it now appears to be genetic in nature. The authors stress the importance of the recognition of the syndrome so that genetic counseling can be offered.