Variable phenotype expression with a frameshift mutation of the cardiac sodium channel gene SCN5A

Loss-of-function mutations in the cardiac sodium channel α-subunit gene SCN5A result in multiple inherited arrhythmic syndromes. This case report describes 2 unrelated probands carrying an identical SCN5A frameshift mutation, V1764fsX1786, who exhibited distinct clinical manifestations: progressive cardiac conduction defect (PCCD)/Brugada syndrome (patient #1) and idiopathic ventricular fibrillation (IVF) (patient #2). Using a whole-cell patch clamp technique, cells expressing V1764fsX1786 showed no observable Na+ current. Therefore, a significant phenotypic overlap was found between IVF and PCCD/Brugada syndrome in the 2 probands with the V1764fsX1786, loss-of-function frameshift mutation of the cardiac sodium channel gene SCN5A.