Familial myoadenylate deaminase deficiency and exertional myalgia.

In 14 members of four families with a hereditary syndrome of exertional myalgia, five of eight muscle biopsies from symptomatic individuals showed histochemical and biochemical absence of myoadenylate deaminase (MADA). In the others, MADA biochemical activity was normal in two and reduced but not absent (intermediate level) in one. Asymptomatic relatives had normal histochemical MADA activity, but three had intermediate biochemical levels. In a survey of 302 routine muscle biopsies, 3 of 36 patient with myalgia had absence of MADA. Three of 266 biopsied for other conditions were MADA-deficient. Despite some inconsistencies, MADA deficiency seems to be relevant to this clinical syndrome.