筋ジストロフィー

Abstract

The “membrane hypothesis” in the pathogenesis of Duchenne muscular dystrophy (DMD) implicates that primary abnormality resides in the membrane system of skeletal muscle and that the abnormality causes progressive breakdown of muscle cells. In DMD, CPK activity in serum is markedly elevated. Histolo gical studies showed that affected muscle contained many “opaque fibers”, or hypercontracted fibers. In these affected fibers, part of plasma membrane was disrupted and xtracellular space tracers invaded muscle cytoplasm. It is postulated that extracellular calcium also gets into sarcoplasm through disintegrated surface membrane and interferes various function of cells.However, the elevation of serum CPK in DMD is explained by the efflux from necrotic muscle cells rather than by the leakage from live cells. Focal loss of plasma membrane might be a reflection of ongoing cell necrosis. Moreover, there is no information about the nature of genetic defect, which is speculated to reside in muscle membrane.The validity of the membrane hypothesis is discussed and other theories on the pathogenesis are also enumerated.