Type IV Branching Enzyme Deficiency

Type IV is an extremely rare disorder manifested by production of an abnormal form of unbranched glycogen in all tissue. Patients exhibit hepatosplenomegaly with ascites and liver failure. Abnormal glycogen can be identified in the tissue and muscles leukocytes or cultured fibroblasts can be used to demonstrate the enzyme deficiency. 

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Glycogenosis type IV (branching enzyme deficiency) results in the formation of a variant of glycogen, characterized by abnormally long inner and outer glucosyl chains and fewer branch points than normal. The abnormal variant is stored in sufficient amounts to cause some vacuolation. The clinical manifestations of this... 

In glycogenosis type III (debranching enzyme deficiency) the absorption maximum is around 410 nm in muscle in liver the maximum remains around 460 nm, but there is a pronounced shoulder at 410 nm. In glycogenosis type IV (branching enzyme deficiency) the absorption maximum is around 530 nm. 

Glycogen Storage Disease Type IV Branching Enzyme Deficiency. 304... 

Several types of glycogen-storage disease are now known in most cases, the accumulation of glycogen can be correlated with a relative deficiency of either n-glucose 6-phosphatase or the debranching-enzyme system (Type I and III disease, respectively). In a very few cases, the enzymic defect is either in branching enzyme or in phosphorylase (Type IV or VI disease, respectively) see Table VII. In the Type II and V diseases, the enzyme deficiencies are different from the above, but have not yet been fully identified. 

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