In Thickness and in Health: Delayed-Onset Pompe Disease Resembling Hypertrophic Cardiomyopathy

Delayed-onset Pompe disease is an extremely rare genetic disease in adults and should be considered in patients with severe left ventricular hypertrophy with left ventricular outflow tract (LVOT) obstruction due to its resemblance to hypertrophic cardiomyopathy (HCM). A case of a 58-year-old woman with no known comorbidities with excellent functional capacity presented because of the gradual onset of exertional dyspnea associated with fatigue, diminished exercise tolerance, occasional exertional chest tightness, and lightheadedness. The electrocardiogram showed left ventricular hypertrophy with T wave inversion in the anterolateral leads. Transthoracic echocardiogram and cardiac magnetic resonance (CMR) showed HCM with LVOT obstruction. Nuclear cardiac scintigraphy was unremarkable for transthyretin cardiac amyloidosis. The patient received a beta blocker and cardiac myosin inhibitor but experienced no change in symptoms. She had a ventriculomyotomy-myectomy and mitral valve repair, which significantly improved her symptoms and resolved the LVOT obstruction. Histology revealed myocyte hypertrophy and both interstitial and endocardial fibrosis. Genetic testing detected a pathogenic c.1841C>T (p.Thr614Met) variant in the acid alpha-glucosidase (GAA) gene linked to autosomal recessive Pompe disease. She is being followed as an outpatient and reports marked improvement in exertional dyspnea and exercise tolerance. She has been referred to a specialist center for enzyme replacement.