Hypertrophic obstructive cardiomyopathy can be the phenotype of storage disorders as
Fabry disease cardiomyopathy. In this instance, its recognition through GLA gene analysis and preventive administration of
enzyme replacement therapy may reduce
heart failure risk of surgical septal myectomy (SSM). A 59-year-old man was referred for SSM as dyspnoea and low threshold muscle fatigue associated to severe
left ventricular outflow obstruction (gradient of 100 mmHg) due to both interventricular septal
hypertrophy and mitral leaflet systolic anterior motion were not controlled by
metoprolol 100 mg bid. Electrocardiogram showed sinus rhythm and a complete
left bundle branch block. Cardiac magnetic resonance imaging showed a preserved left ventricular (LV) contractility (ejection fraction 70%) but failed to reveal reduced T1 mapping and
fibrosis of postero-lateral LV wall suggesting
Fabry disease cardiomyopathy. Cardiac catheterization and coronary angiography documented increased LV end-diastolic pressure but normal coronary arteries. SSM was followed by acute renal and
heart failure with left ventricular ejection fraction declining to 35%. Histology of SSM showed regularly arranged severely enlarged cardiomyocytes containing extensive vacuoles that were intensely positive to immunofluorescence with anti-Gb3
antibodies and appeared at electron microscopy to consist of myelin bodies suggesting the diagnosis of FD. This entity was confirmed by low blood levels of
alpha-galactosidase A (0.8 nmol/mL/h; NV > 1), high values of
Lyso-Gb3 (5.85 nmol/L; NV < 2.3), and the presence of the pathogenic mutation c.644A>G in the exon 5 of GLA gene. This study emphasizes the importance of a genetic screening for FD before SSM be considered for
hypertrophic obstructive cardiomyopathy.