Several rare mutations associated with familial lone atrial fibrillation (AF) have been identified; however, the phenotypes are varied and poorly elucidated.Here, we report a 29-year-old woman with AF refractory to anti-arrhythmic drugs. Her family history revealed early-onset and persistent AF in her father and brother as well. Genetic analysis subsequently demonstrated a c.421G>A mutation in the KCNQ1 gene. Unique phenotypes including absence of both atrial appendages, extremely high atrial frequencies, and refractoriness to both ablative and pharmacological therapy were observed. Our study suggests the need for further exploration of the function of KCNQ1 and the mechanism of AF.