Expanding the genotype-phenotype spectrum in SCN8A-related disorders

SCN8A-related disorders are a group of variable conditions caused by pathogenic variations in SCN8A. Online Mendelian Inheritance in Man (OMIM) terms them as developmental and epileptic encephalopathy 13, benign familial infantile seizures 5 or cognitive impairment with or without cerebellar ataxia. In this study, we describe clinical and genetic results on eight individuals from six families with SCN8A pathogenic variants identified via exome sequencing. Clinical findings ranged from normal development with well-controlled epilepsy to significant developmental delay with treatment-resistant epilepsy. Three novel and three reported variants were observed in SCN8A. Electrophysiological analysis in transfected cells revealed a loss-of-function variant in Patient 4. This work expands the clinical and genotypic spectrum of SCN8A-related disorders and provides electrophysiological results on a novel loss-of-function SCN8A variant.