Any familial atrial fibrillation in which the cause of the disease is a mutation in the KCNQ1 gene. The disease is atrial fibrillation, familial, 3 (MONDO_0011857). Also known as: KCNQ1 familial atrial fibrillation, atrial fibrillation, familial, type 3, familial atrial fibrillation caused by mutation in KCNQ1.