A 5-month-old infant presents with generalized hypotonia, macroglossia, and striking cardiomegaly with biventricular hypertrophy. Serum CK is elevated. Muscle biopsy shows vacuoles filled with periodic acid-Schiff positive material, and acid alpha-glucosidase activity in fibroblasts is absent. What is the diagnosis?

• A Danon disease (LAMP2 deficiency)
• B Pompe disease (glycogen storage disease type II) ✓
• C Debrancher deficiency (glycogen storage disease type III)
• D Liver phosphorylase kinase deficiency

Explanation

Pompe disease is caused by deficiency of lysosomal acid alpha-glucosidase (acid maltase). Glycogen accumulates inside lysosomes, producing the vacuolated PAS-positive biopsy, and cardiac involvement dominates the infantile form, unlike other glycogen storage diseases. Hypotonia, macroglossia, and cardiomyopathy are classic. Danon disease also causes cardiomyopathy but is an X-linked membrane protein disorder without glycogen-filled lysosomes. Enzyme replacement therapy with alglucosidase alfa is available.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.