Myoadenylate deaminase deficiency.

This report concerns two unrelated males; one had sarcoidosis, sarcoid myopathy and muscle weakness, and the other had exercise-induced weakness and myalgia. Both patients had a lack of ammonia rise in their serum after an ischemic work test, minimal histochemical activity of myoadenylate deaminase in repeated muscle biopsies, and less than 5% of normal biochemical activity of myoadenylate deaminase in their skeletal muscles. These three criteria establish primary myoadenylate deaminase deficiency as a separate primary metabolic muscle disease which merits differential diagnostic consideration when patients complain of muscle weakness and cramps.