A 35-year-old male with history of recurrent arrhythmias presented for pulmonary vein isolation. He underwent pre-procedural screening for thromboembolism risk with transesophageal echocardiogram. He had an incidental finding of a rare fenestrated membrane overlying his left atrial appendage. Additional work-up throughout his clinical course revealed genetic mutations in the LMNA and SNTA1 genes. There have been no previous reported genetic mutations reported in cases with LAA membranes.