Myosin inhibitor therapy in Fabry cardiomyopathy with dynamic left ventricular outflow obstruction.

A 56-year-old woman with presumed hypertrophic cardiomyopathy was diagnosed with Fabry disease (GLA: p.Glu358del) and a concomitant PLN variant. Imaging revealed advanced Fabry cardiomyopathy with dynamic LVOT obstruction. Despite optimized medical and enzyme replacement therapy, symptoms progressed (NYHA-class III) with a marked increase in LVOT gradient. Mavacamten was initiated and uptitrated under echocardiographic monitoring. At three months, LVOT gradient significantly decreased and functional status improved (NYHA-class I), while systolic function remained preserved. This case highlights the importance of detailed phenotyping and suggests that myosin inhibition may represent a therapeutic option for LVOT obstruction beyond classical sarcomeric hypertrophic cardiomyopathy.