Glycogen storage disease confined to the heart with deficient activity of cardiac phosphorylase kinase: a new type of glycogen storage disease.

The case of a male infant with marked deposition of glycogen, confined to the heart, is presented. Clinically, prominent cardiomegaly had been evident from immediately after birth until the infant's death due to heart failure. There were no significant clinical manifestations in other organs, including liver and skeletal muscle, during the clinical course. Autopsy revealed abnormal deposition of normally structured glycogen in the heart, but no deposition in the liver, skeletal muscle, or other systemic organs. This unusual pattern of glycogen deposition was also confirmed by measurement of the glycogen content of each organ. This is the first report of glycogen storage disease confined to the heart. Enzymatic analysis revealed no decrease in the activities of acid maltase, amylo-1,6-glucosidase, and phosphorylase in the heart or in the liver or skeletal muscle. However, phosphorylase kinase activity was not detectable in the heart, although high activity levels were observed in the liver and skeletal muscle. In this case the inborn error of metabolism responsible for the isolated deposition of glycogen in heart muscle may have been due to a deficiency of cardiac phosphorylase kinase.