SCN2A-Related Early-Onset Epileptic Encephalopathy Responsive to Phenobarbital

Epilepsy-Related Voltage-Gated Sodium Channelopathies: A Review

Epilepsy is a disease characterized by abnormal brain activity and a predisposition to generate epileptic seizures, leading to neurobiological, cognitive, psychological, social, and economic impacts for the patient. There are several known causes for epilepsy; one of them is the malfunction of ion channels, resulting from mutations. Voltage-gated sodium channels (NaV) play an essential role in the generation and propagation of action potential, and malfunction caused by mutations can induce irregular neuronal activity. That said, several genetic variations in NaV channels have been described and associated with epilepsy. These mutations can affect channel kinetics, modifying channel activation, inactivation, recovery from inactivation, and/or the current window. Among the NaV subtypes related to epilepsy, NaV1.1 is doubtless the most relevant, with more than 1500 mutations described. Truncation and missense mutations are the most observed alterations. In addition, several studies have already related mutated NaV channels with the electrophysiological functioning of the channel, aiming to correlate with the epilepsy phenotype. The present review provides an overview of studies on epilepsy-associated mutated human NaV1.1, NaV1.2, NaV1.3, NaV1.6, and NaV1.7.

De novo SCN2A mutation in a Chinese infant with severe early-onset epileptic encephalopathy, bronchopulmonary dysplasia, and adrenal hypofunction

Early-onset epileptic encephalopathies (EOEEs) are a group of phenotypically and genetically heterogeneous neurodevelopmental disorders. Mutations of SCN2A, the gene encoding the aII subunit of the voltage-gated sodium channel (Nav1.2), have been detected in some EOEE patients. This report describes a 4-month-old female who presented with severe EOEE as well as bronchopulmonary dysplasia and adrenal hypofunction. Whole-exome sequencing revealed a novel missense mutation in SCN2A (c.1261T > G; p.L421V) that was not detected in either her parents or her brother. The mutation was confirmed by Sanger sequencing and characterized as pathogenic by several prediction programs. This finding of a de novo SCN2A mutation in an ethnic Chinese infant with EOEE as well as multi-organ dysfunction expands the phenotypic spectrum of SCN2A mutations.