glycogen storage disease type-III (Cori-Forbes type glycogen storage disease)

Classification: 3-4 types recognized: - GSD type 3A patients lack glycogen debrancher enzyme activity in both liver & muscle - GSD type 3B patients are enzyme-deficient in liver only - GSD type 3C (rare) selective loss of only 1 of the 2 debranching activities, the glucosidase activity - GSD type 3D (rare) selective loss of only 1 of the 2 debranching activities, the transferase activity Pathology: - accumulation of abnormal glycogen with short outer chains Genetics: - associated with defect in AGL gene Clinical manifestations: - variable degrees of hepatomegaly, muscle weakness, fasting hypoglycemia, short stature Laboratory: - normal response of plasma glucose to IM glucagon after food; poor after fasting - AGL gene mutation - amylo-alpha-1,6-glucosidase in leukocytes

Properties

DEFICIENT-PROTEIN: glycogen debranching enzyme MOTIF: 4-alpha-glucanotransferase {1} aspartate residue {D526} histidine residue {H529} aspartate residue {D627} Amylo-1,6-glucosidase {1532}

References

Clinical Diagnosis & Management by Laboratory Methods, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1991, pg 185