Evidence of evolution towards left midventricular obstruction in severe Anderson–Fabry cardiomyopathy

Aims: In Fabry cardiomyopathy, left ventricular outflow tract obstruction mimicking hypertrophic cardiomyopathy is a very rare finding, with few cases reported and successfully treated with cardiac surgery. In our population of patients with Fabry disease and severe left ventricular hypertrophy (LVH) at the time of diagnosis, we observed an evolution towards a midventricular obstructive phenotype. Methods and results: We present a case series of three classically affected Fabry male patients with significant diagnostic delay and severe cardiac involvement (maximal wall thickness >20 mm) at first evaluation. All patients developed midventricular obstructive form over time despite prompt initiation and optimal compliance to enzyme replacement therapy. The extension and distribution of the LVH, involving the papillary muscles, was the main mechanism of obstruction, unlike the asymmetric septal basal hypertrophy and the mitral valve abnormalities commonly seen as substrate of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy. Conclusions: Fabry cardiomyopathy can evolve over time towards a midventricular obstructive form due to massive LVH in classically affected men with significant diagnostic delay and severe LVH before enzyme replacement therapy initiation. This newly described cardiac phenotype could represent an adverse outcome of the disease.