SCN1B variants are linked to DEE52 as well as to cardiac disease, including Brugada Syndrome 5 (BrS5, OMIM 612838) and Atrial Fibrillation Familial 13 (OMIM 615377), although there is evidence to suggest that SCN1B may not be a monogenic cause of BrS (32). Here, SCN1B is linked to Familial progressive cardiac conduction defect.