Glycogen 33 



The cardiac type of generalised glycogen disease— sometimes 

 called Pompe's disease— is much less common, for no more than 

 twenty cases have been recorded. The heart muscle is heavily in- 

 filtrated with normal glycogen which interferes mechanically with 

 the muscle fibres and proves fatal in a few months. The glycogeno- 

 lytic function of the liver is preserved and carbohydrate function 

 proceeds normally. The cause of the defect is unknown. In another 

 closely related variety, the striated muscles are heavily infiltrated 

 with normal glycogen, but the heart muscle escapes. Tests of carbo- 

 hydrate function are normal; the nature of this condition remains 

 a mystery. 



Two varieties of storage disease have been distinguished in 

 which abnormal glycogen is stored in the liver and cells of the 

 reticulo-endothelial system. In one instance, absence of amylo-1,6- 

 glucosidase activity (Debrancher) leads to the production of a 

 glycogen molecule with short, outer branches that resemble a "limit 

 dextrin." In the other form, glycogen possesses few and excessively 

 long outer branches which are thought to be due to inhibition of 

 the branching enzyme. Only one case has so far been reported on 

 which chemical studies have been carried out. The glycogen is 

 similar to the amylopectin of corn and seems to behave as a foreign 

 substance in the body, provoking a fibrous reaction in the liver and 

 kidneys. 



GLYCOGEN VARIATION IN DISEASE 



A glycogen increase in the cells of the liver, kidneys and heart 

 muscle— occasionally in a great variety of cells— has long been 

 recognised as a characteristic feature of diabetes mellitus. The 

 vacuolated appearance of the /? cells of the islets of Langerhans, 

 found in human and experimental diabetes, is now known to be 

 a sign of glycogen accumulation. Frequently the nuclei of liver 

 cells are also affected. The explanation seems to be that the first 

 step of glycogen manufacture— the formation of glucose-6-phos- 

 phate— is deficient and glucose piles up in the tissues and blood and 

 overflows into the urine. Studies on liver slices with intact cells 

 from diabetic animals have disclosed two blocks in the metabolism 

 of glucose. One is somewhere between glucose and fructose phos- 



