A 12-Year-Old Girl with a 2-Year History of Progressive Limb Weakness and Difficulties with Exercise

Pompe disease is an autosomal recessive disease caused by mutations in the lysosomal acid alpha-1,4 glucosidase (GAA) leading to a deficiency of the enzyme acid alpha glucosidase, also known as acid maltase with secondary accumulation of glycogen in lysosomes. There is a wide range of age at symptom onset. The disease can manifest from the severe infantile form with hypertrophic cardiomyopathy to the adult onset milder form with myalgias and muscle weakness. Diagnosis is confirmed by measuring GAA enzyme activity and subsequent gene test. Histologically the muscle biopsy reveals a vacuolar myopathy with lysosomal glycogen storage abnormalities. Treatment involves enzyme replacement therapy.