Prevalence and clinical features of Fabry disease in Japanese male patients with diagnosis of hypertrophic cardiomyopathy

BACKGROUND: The prevalence of Fabry disease (FD) in Japanese patients presenting with unexplained left ventricular hypertrophy (LVH) has remained unclear. METHODS: We measured plasma α-galactosidase A activity in 177 men with a diagnosis of hypertrophic cardiomyopathy (HCM) (maximum LV wall thickness ≥15mm). RESULTS: Two patients (1.1%) showed very low α-galactosidase A activity [0.0 and 0.3nmol/hr/ml (normal range: 3.6-17.6nmol/hr/ml)], and a clinical diagnosis of cardiac variant of FD was finally made. One patient was a 55-year-old man who came to our hospital because of abnormal results of electrocardiography and showed concentric LVH in echocardiography. A missense mutation, R112L, was identified. The other was a 74-year-old man who had been diagnosed with HCM at the age of 60 years in another hospital and was referred for evaluation of repeated hospitalization for heart failure. Although echocardiography revealed asymmetric septal hypertrophy (ASH) with interventricular septal wall thickness of 16mm and posterior wall thickness of 11mm and reduced LV ejection fraction with hypokinetic posterior wall motion, his echocardiographic findings at the initial diagnosis of HCM were not ASH but concentric LVH with normal LV systolic function. A splicing mutation, IVS4+919G>A, was identified. CONCLUSIONS: The prevalence of FD in Japanese male patients with a clinical diagnosis of HCM was found to be 1.1%. These patients showed late onset and concentric LVH at initial presentation.