Determination of SCN1A genetic variants in Mexican patients with refractory epilepsy and Dravet syndrome

Mutations in the SCN1A gene can result in syndromes associated with epilepsy, including the Dravet syndrome (DS). However, the prevalence of such mutations in these diseases varies widely between different studies, and has not been examined in Mexican patients with epilepsy. Therefore, the objective of this study was to determine the frequency of SCN1A mutations (in the exon 26) in a cohort of Mexican patients with DS and refractory epilepsy (RE). We recruited 24 Mexican patients (14 males and 10 females), of which 15 were diagnosed with RE and 9 were diagnosed with DS. The SCN1A gene was sequenced to uncover mutations in exon 26. We detected 2 novel genotypes in 2 DS patients. One was a synonymous variant, c.5418 G > A (E1806E), and the other was a missense variant, c. 5324 T > C (L1775P). The missense mutation was predicted to be damaging with a score of 100% by the PolyPhen-2 program. The frequency of pathogenic variants was 4.17% in all the patients and 11.1% in DS patients, which, together with other publications, emphasize that specific and more severe phenotypes are associated with SCN1A mutations.