Glycogen Storage Disease II

The pale, greatly enlarged heart with thick walls is from an infant with Pompe disease.

The myofibers are engorged with glycogen. On cross sections the myofibrils are pushed to the periphery. Despite the thick walls, this is not hypertrophy. These patients present with congestive failure. 

Glycogen storage diseases (GSD) result from hereditary deficiency of various enzymes involved in the synthesis or degradation of glycogen. According to the enzyme involved, glycogen storage may be predominant in either liver, skeletal muscle, or myocardium. GSD II (Pompe disease) is an autosomal recessive disease due to a mutation of the gene encoding acid alpha-1,4-glucosidase, The disease can be clinically separated into 3 forms; infantile, juvenile, and adult-onset. Cardiac involvement is most prominent in the infantile form. These infants usually present within the first few months of life and die within the first year because of the cardiac involvement. In this GSD, the liver is not usually primarily enlarged but hepatosplenomegaly can result from right heart failure.