Myoadenylate deaminase deficiency: a new disease of muscle.

Five cases of a new disease presented with muscular weakness or cramping after exercise; three of the cases also had an elevated serum creatine phosphokinase. Muscle biopsies were histologically normal but lacked adenylate deaminase by stain and solution assay, while the erythrocyte isozyme was normal. A clinical diagnostic test has been developed, and the human enzyme was separated by acrylamide-gel electrophoresis.