Clinical, neurological, and molecular genetic studies of 22 patients with diagnostic features of Angelman syndrome (AS) are reported from National Taiwan University Hospital, Taipei. A deletion of region 15qll-13 was identified cytogenetically in 11 cases by high-resolution technique. Four cases were confirmed by fluorescence in situ hybridization (FISH). The remaining 7 cases had no deletions over 15qll-13. Clinical features of AS were obvious after 2 years of age. During infancy AS may be mistaken for Rett syndrome, ataxic cerebral palsy, Prader-Willi syndrome, or infantile autism. 
COMMENT. Seizures occur in 80% of cases of Angelman syndrome, usually by 2 years of age, and Boyd and colleagues, Great Ormond Street Hospital, London, have described characteristic EEG findings that are included among diagnostic criteria for AS. In the above report, EEG findings were sometimes absent at an early age, and cytogenetic confirmation of the diagnosis was stressed.