[Exercise-induced muscular weakness, myalgia and contractures. II. Casuistic contribution].

Two sisters with exercise-induced myalgias, muscular weakness and contractures are reported. Neurologic and psychiatric findings were normal, nor did electromyography, serum enzymes and ischemic forearm exercise test reveal specific findings. Under the light microscope multiple muscle fibers contained small vacuoles which stained positive with Oil Red O. No further information resulted from histochemical examinations. In the more seriously affected patient morphometric analysis of electronmicrographs showed a tenfold increase of fat content in comparison to normal controls. Alterations in the enzymatic activities could be demonstrated in glycogenolysis, glycolysis and in fat metabolism, but there were no previously described enzyme defects such as phosphorylase deficiency, phosphofructokinase deficiency, phosphohexoisomerase inhibitor, carnitine or carnitine-palmityltransferase deficiency. Myopathy with lactic acidosis, prolonged muscular relaxation due to deficient reabsorption of sarcoplasmic calcium in the tubular system and dyskalemic paralysis can be ruled out on the basis of the clinical signs. This myopathy may be due to an as yet unknown metabolic disturbances.