The clinical Angelman Syndrome phenotype spectrum, with particular attention to the epilepsy, in patients with different genetic abnormalities at the 15q11-q13 region

Angelman syndrome (AS) is a neurodevelopmental disorder characterised by severe developmental delay, iperkinetic movement disorder,a happy and sociable disposition and profound speech impairment. Four genetic mechanisms are known leading to AS. We describe 5 patients with AS and different genetic abnormalities at the 15q11-13 region: 15q11-q13 maternal deletion (1) and 15q11.2 microdeletion (1), uniparental disomy paternal -UDP (1), imprinting defects-ID (1) and UBE3A gene mutation (1). The genotype-phenotype correlation detects a phenotypic spectrum, from the patient with deletion more seriously affected to the UDP and ID cases with milder phenotype. The patient with the 15q11.2 microdeletion shows atypical clinical features of a Pervasive Developmental Disorder Non Otherwise Specified (PDD-NOS) and a characteristic EEG pattern of "notched delta". We confirm both the phenotypic spectrum related to the different genetic classes of AS and the "notched delta" pattern EEG as a meaningful detection tool for AS also in atypical phenotype.