Type V Muscle Phosphorylase Deficiency

Type V, also called McArdle s disease, usually presents in the second or third decade with muscle cramps after exercise. Moderate exercise can be sustained, and patients have a second wind, when symptoms disappear if exercise is continued. Increased plasma creatine kinase activities at rest, the failure of ischemic exercise to increase serum lactate concentrations while producing an exaggerated increase in ammonia, myoglobinuria, and diminished activity of muscle phosphorylase establish the diagnosis. Patients respond to oral glucose administration or injections of glucagon. 

Type VI (Liver Phosphorylase or Phosphorylase Kinase Deficiency) 

Patients with this rare type have deposits of abnormal glycogen in muscle. Exercise intolerance, unresponsiveness to glucose administration, and hemolysis (caused by decreased glycolysis in erythrocytes) are noted clinically, producing hyperbilirubinemia, pigmenturia, and reticulocytosis. The specific enzyme defect can be demonstrated. 

Alberti KG, Zimmet PZ. Definition, diagnosis and classification of diabetes mellitus and its complications, Part 1 diagnosis and classification of diabetes mellitus provisional report of a WHO consultation. Diabet Med 1998 15 539-53. 

Allen BT, DeLong ER, Feussner )R. Impact of glucose self-monitoring on non-insulin-treated patients with type II diabetes mellitus. Randomized controlled trial comparing blood and urine testing. Diabetes Care 1990 13 1044-50. 

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