Both index patients were free of mutations in genes previously associated with AF (KCNQ1, KCNH2, KCNN3, KCNA5, KCNE2/3/5, KCNJ2,5, SCN5A, SCN1-3B, ANP, and LMNA). The gene discussed is KCNA5; the disease is atrial fibrillation.