Epilepsy and cataplexy in Angelman syndrome. Genotype-phenotype correlations.

Background: Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability, epilepsy, and low threshold for laughter.

Aims: We investigated the occurrence and severity of epilepsy and laughter-induced loss of postural muscle tone determined by the different genetic subtypes.

Methods: This study included 39 children with AS. Deletion breakpoints were determined by high resolution CGH microarray (1×1M Agilent). Clinical data were based on a parent interview and medical record review.

Results: All patients with AS based on a deletion had epilepsy. Epilepsy was present in 3/4 children with UBE3A mutation, and 4/5 with pUPD. Onset of epilepsy occurred earlier in deletion cases compared to pUPD or UBE3A mutations cases. Laughter-induced postural muscle tone loss occurred only among deletion cases. We found no differences in severity of epilepsy between children with a larger Class I or a smaller Class II deletions, or between the total group with a deletion compared to children with pUPD or a UBE3A mutation. The drugs most frequently prescribed were benzodiazepines in monotherapy, or a combination of benzodiazepines and valproic acid.

Conclusion: Epilepsy is very common in patients with AS, especially in patients with a deletion. Postural muscle tone loss and collapsing during outbursts of laughter were seen in patients with a deletion only.