Glycogen storage disease type IV, amylopectinosis.

Classification of the glycogen storage diseases according to the underlying enzyme defect has added considerably to our understanding of this group of diseases. Of the 6 types in which the bio- chemical abnormality has been characterized, the least common appears to be type IV, amylopectin- osis. The first case was described by Andersen in 1952, and the glycogen present in the liver and other organs was shown by Illingworth and Cori (1952) to possess abnormally long outer and inner chains of glucose units. For this reason, Cori (1954) suggested that the enzyme, oc-1,4-glucan: oc-1,4 glucan 6-glycosyl transferase, effective in transferring chains of glucose units to form new branches in the glycogen molecule, was absent.