[Silent exercise-induced enzymatic myopathies at rest in adults. A cause of confusion with fibromyalgia].

Exercise-induced enzymatic myopathies include carnitine palmityl transferase deficiency and, among muscular glycogenoses, Mac Ardle's and Tarui diseases. These diseases are usually recognized when exercise-induced myalgias, myoglobinuria and raised creatinine kinase (CK) levels are present. However, myoglobinuria may be absent in 10 to 50 percent of the cases, and CK levels are often normal at rest; thus, the diagnosis is often delayed for several years, with a risk of acute renal failure in 10 to 30 percent of the patients. We report 6 cases of exercise-induced enzymatic myopathies with normal CK levels and with electromyographic studies at rest. The main clinical features of these cases and those of similar conditions reported in the literature are male sex, onset of the disease before the age of 15 years, episodes of severe exercise-induced myalgias, cramps and muscle weakness and myogenic hyperuricaemia at rest in muscular glycogenosis.