KCNQ1 and Inherited cancer-predisposing syndrome: Clinical interventions after identification of germline mutations included familial cascade testing for patients with BRCA2 (n = 1) and SCN5A (n = 1) germline mutations, cardiac workup and lifestyle modifications for patients with SCN5A (n = 1), KCNQ1 (n = 1), and DSC2 (n = 1) germline mutations, initiation of early colorectal cancer screening for a MUTYH carrier based on carrier status and family history (n = 1), and more complete hereditary cancer syndrome germline testing due to a suggestive family history for an MUTYH carrier (n = 1).