GLYCOGEN STORAGE DISEASE OF THE HEART

Abstract

Glycogen storage disease of the heart is a separate disease entity with distinctive manifestations. Clinical, chemical and pathologic criteria for diagnosis are listed. In a survey of the literature 14 cases were found that fulfilled all requirements. The impression given by the available clinical data is that of an illness remarkably constant in its course and manifestations. Eleven of the 14 patients died between the ages of 4 and 8 months, and the other three at an earlier age. The electrocardiographic findings in three cases are discussed. The pathologic changes were similar in all cases. The outstanding lesions were in the myocardium, but abnormal deposition of glycogen was not limited to this site, being found in many other organs and tissues. In 6 out of 8 cases in which histologic and histochemical studies of skeletal muscles were made, a distinctive type of degeneration was found together with an abnormally great accumulation of glycogen. Analyses of blood and urine performed while the patients were still living were essentially normal. Postmortem chemical studies in six cases confirmed the morphologic demonstration of widespread distribution of glycogen throughout the body. Spontaneous glycogenolysis was shown to occur in the myocardium after incubation at 37° C. for 24 to 48 hours, although to a different degree in the three cases in which it was done. In two of these there was virtually complete disappearance of glycogen from the liver after incubation at 37° C. for 24 to 48 hours. The cause of this rare disease is presumably an inborn error of metabolism transmitted as a recessive genetic character. Whatever the mechanism the condition is incompatible with life for more than a few months, during which cardiac function continually regresses. The most plausible explanation is that the accumulation of glycogen in the myocardial fibers progresses to a point where their contraction is impaired and effective cardiac action is no longer possible. It is pointed out that the term "glycogen storage disease of the heart" is a misnomer, since the disease process is not limited to this organ. On the other hand, as tradition has sanctioned its use, the name may well be retained. A plea is entered for dropping the name "von Gierke's disease of the heart" as leading to confusion with other types of glycogen storage disease. The clinical and metabolic differences between the hepatic and cardiac types of glycogen storage disease are detailed. Other conditions characterized by abnormally great accumulation of glycogen in the myocardium, such as congenital rhabdomyoma of the heart, socalled cardiomegalia glycogenica circumscripta, and occasional cases in which death is sudden though not always explained, are described and the differences with glycogen storage disease of the heart mentioned. Differential diagnosis is discussed and it is pointed out there are no pathognomonic signs or laboratory investigations, except for the histochemical demonstration of abnormal amounts of glycogen in the skeletal muscles. It is suggested that biopsy of skeletal muscle be performed in all cases in which unexplained enlargement of the heart in infancy occurs. This is essential in order to plan ante- and postmortem pathologic and chemical studies.