Angelman syndrome (AS) is characterized by severe mental retardation, epilepsy, absent speech, dysmorphic facial features, and a characteristic behavioral phenotype. It is caused by deficiency of gene expression from maternally derived chromosome 15q11-q13.
The authors present the clinical picture of 9 children (median age, 4.9 years; range, 1 to 10 years) with confirmed Angelman syndrome. The patients complied with the international consensus criteria for AS and were consecutively investigated for psychomotor development, epilepsy, and electroencephalogram (EEG) profiles.
The median age at diagnosis was 3.9 years. The motor milestones were delayed. Median developmental quotient level was 26. All patients but 1 experienced predominantly polymorphic seizures. In 4 cases, the epilepsy was refractory to treatment. The EEG of all patients displayed an abnormal sleep pattern and generalized abnormalities, with a maximum over the posterior areas.
Milder or less typical phenotypes of AS may remain undiagnosed, leading to an overall underdiagnosis of the disease. The EEG shows no clear relation to genotype, clinical picture, or to the presence and severity of epilepsy. AS should be considered in the differential diagnosis of children with severe cryptogenic epilepsy and a characteristic configuration of clinical features.