Angelman syndrome (AS) is a distinct neurogenetic disorder and the phenotype is well known in childhood and adolescence. However, with advancing age the clinical and behavioral phenotype changes. In adulthood, the phenotype can be rather aspecific. We report on AS in 3 severely to profoundly mentally retarded patients, who developed severe neurologic complications of severe tremor, spasticity and coordination problems, resulting into severe loss of function. They presented atypical craniofacial features, short stature, epileptic seizures, microcephaly, brachytelephalangy and absent speech. Two patients presented at an older age a change in day-night rhythm. Based on this experience, we conclude that all severely to profoundly mentally retarded patients with atypical phenotype, spasticity, absent speech, epileptic seizures and changed day-night rhythm are candidates for further cytogenetic and molecular investigation for AS. Clinical photographs of the patient at a younger age can be helpful. The presence of the typical EEG pattern with frontal triphasic delta waves may direct to the diagnosis of AS.
