Severe Cardiomyopathy as the Isolated Presenting Feature in an Adult with Late-Onset Pompe Disease: A Case Report.

Many inborn errors of metabolism can cause cardiomyopathy. Cardiomyopathy associated with glycogen storage includes PRKAG2-associated glycogen storage disease (GSD), Danon disease, infantile-onset Pompe disease (GSD II), GSD III, GSD IV, and phosphofructokinase deficiency (Tarui disease or GSD VII).We present a 35-year-old female who presented with cardiomyopathy after a pregnancy complicated by primary hyperparathyroidism. She had enjoyed excellent health until her first pregnancy at age 33. One week postpartum, she developed dyspnea and an echocardiogram revealed left ventricular ejection fraction (LVEF) of 35%. A cardiac MRI was consistent with nonischemic cardiomyopathy with an infiltrative process. Endomyocardial biopsy showed striking sarcoplasmic vacuolization, excess glycogen by PAS staining, and frequent membrane-bound glycogen by electron microscopy, consistent with lysosomal GSD. Acid alpha-glucosidase (GAA) activity in skin fibroblasts was in the affected range for Pompe disease. Sequencing of the GAA gene revealed a paternally inherited pathogenic c.525delT (p.Glu176Argfs*45) and a de novo c.309C>G (p.Cys103Trp) with unknown pathogenicity. Testing of the familial mutations in her daughter indicated that the variants in the proband were in trans. 26-gene cardiomyopathy sequencing panel had normal results thereby excluding GSD III, Danon disease, Fabry disease, and PRKAG2-associated cardiomyopathy. Therefore, results strongly suggest a diagnosis of Pompe disease.Pompe disease has a broad disease spectrum, including infantile-onset (IOPD) and late-onset (LOPD) forms. LOPD typically presents with proximal muscle weakness and respiratory insufficiency in childhood or late adulthood. Our case may represent a very unusual presentation of adult LOPD with isolated cardiomyopathy without skeletal muscle involvement or respiratory failure.