The long-term effects of enzyme replacement therapy (ERT) on cardiac function and the conduction system in Fabry disease are not clearly understood. We report a case of a 48-year-old man with non-classical Fabry disease treated with ERT for 11 years. He was diagnosed with Fabry disease at age 27 years based on the presence of decreased alpha-galactosidase A activity in the peripheral leukocytes and of the causal alpha-galactosidase A mutation (Val339Gln). Subsequently, peritoneal dialysis was initiated for renal failure at age 35 years. ERT was initiated at age 39 years to halt the progression of cardiac dysfunction. Electrical conduction disturbances progressed gradually to complete atrioventricular block with atrial standstill during 9 years of ERT despite the lack of progression of ventricular hypertrophy. Although he underwent permanent pacemaker implantation to prevent sudden cardiac death, the atrioventricular junctional rhythm remained, thereby lowering the ventricular pacing rate. Based on this case, we recognize that the effects of ERT are limited for inhibiting the progression of Fabry disease and especially for inhibiting arrhythmia and conduction disturbances. Early diagnosis of Fabry disease and early initiation of ERT might be the key to further improvements in this disease and its associated conditions. .