Myopathy caused by a deficiency of Ca2+-adenosine triphosphatase in sarcoplasmic reticulum (Brody's disease).
Four male patients from two families were first seen with impaired skeletal muscle relaxation that rapidly worsened during exercise. Muscle biopsies from 2 patients were examined by appropriate biochemical and microscopic immunocytochemical techniques. The adenosine triphosphate (ATP)-dependent Ca2+ transport rate was extremely low in a particulate membrane fraction of skeletal muscle, and there was also a marked reduction of the concentration of 100-kD phosphoprotein, corresponding to Ca2+-ATPase of sarcoplasmic reticulum, in muscle microsomes. The concentration of immunoreactive Ca2+-ATPase of sarcoplasmic reticulum was markedly reduced on immunoblots. Evaluation by microscopic immunocytochemical techniques, using one polyclonal and two monoclonal antibodies against sarcoplasmic reticulum Ca2+ transport protein, revealed that the severe reduction of immunoreactive Ca2+-ATPase was limited to the histochemical type 2 fibers. The deficiency of the Ca2+ transport protein in the sarcoplasmic reticulum of type 2 fibers, which may be the primary expression of a presumed gene defect, can explain the impaired muscle relaxation of the patients. This disease appears to be a clinically, electromyographically, and biochemically distinct metabolic myopathy.
D000328:Adult; D000252:Calcium-Transporting ATPases / Q000032:analysis / Q000172:deficiency* / Q000378:metabolism; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D009119:Muscle Contraction; D009126:Muscle Relaxation; D009135:Muscular Diseases / Q000201:enzymology* / Q000235:genetics; D010750:Phosphoproteins / Q000096:biosynthesis; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013577:Syndrome
D010750:Phosphoproteins; D000252:Calcium-Transporting ATPases