Infantile epilepsy associated with mosaic 2q24 duplication including SCN2A and SCN3A

Epilepsies can be caused by specific genetic anomalies or by non-genetic factors, but in many cases the underlying cause is unknown. Mutations in the SCN1A and SCN2A genes are reported in childhood epilepsies; in particular SCN1A was found mutated in patients with Dravet syndrome and with generalized epilepsy with febrile seizures plus (GEFS+). In this paper we report a patient presenting with an atypical epileptic syndrome whose phenotype partially overlaps both Dravet syndrome and benign familial neonatal-infantile seizures (BFNIS). Array-CGH analysis suggested the presence of a mosaic duplication (about 12Mb) at the level of chromosome 2q23.3q24.3 involving SCN2A and SCN3A genes. Additional analyses (radiolabeled RFLP and quantitative PCR) confirmed the mosaicism of the duplication. We suggest that the array-CGH analysis is mandatory for children presenting with epilepsy and psycho-motor retardation even without dysmorphisms or other clinical features suggesting a specific genetic/epileptic syndrome. The analysis must nevertheless be performed taking into account the possibility of a mosaicism.