Congenital neuromuscular variant of glycogen storage disease type IV presenting as hypertrophic cardiomyopathy

Glycogen storage disease (GSD) type IV is an autosomal recessive disorder due to a deficiency of glycogen branching enzyme (GBE), leading to accumulation of polyglucosan inclusion in tissues. The congenital neuromuscular variant is a severe subtype presenting as hypotonia, respiratory distress and dilated cardiomyopathy, resulting in early death. Cardiac manifestations as a primary presentation are uncommon in this subtype. We report the case of a male preterm infant who presented with heart failure attributed initially solely to hypertrophic cardiomyopathy. Genetic testing identified compound heterozygous GBE1 variants. Enzymatic testing demonstrated reduced GBE activity, and histopathological findings showed myocardial Periodic acid-Schiff-positive and diastase-resistant inclusions, confirming the diagnosis. Neurological symptoms developed later, increasing the suspicion of a metabolic disorder. This case represents a unique presentation of this variant of GSD IV, primarily manifesting with hypertrophic cardiomyopathy. It underscores the importance of considering metabolic disorders in infants with cardiomyopathy, even when neurological symptoms are initially absent.