Multicore myopathy--a case report.

Multicore myopathy is a rare congenital myopathy. The multicores consist of numerous small areas of decreased oxidative enzyme activity. The long axis of the lesion is perpendicular or parallel to the long axis of the muscle fiber. These cores are usually smaller than central cores. For this reason they are also called minicores. Although the multicores represent a nonspecific change in that they can be observed in malignant hyperthermia, muscular dystrophy, inflammatory myopathy, etc. Muscular weakness dating from early infancy is combined large proportion of the muscle fibers. In about half of the reported cases the muscular weakness has not been progressive, while in the others a slow progression has occurred. This 9-year-old boy presented with congenital nonprogressive myopathy associated with thoracic scoliosis and bilateral equinovarus deformity. The serum creatine phosphokinase and lactic dehydrogenase levels were normal. Electromyography showed "myopathic" features. The biopsy revealed a marked size variation in myofibers, ranging from 10 microns to 100 microns. A few small angular fibers and slight endomyseal fibrosis were also noted. There was type I fiber predominance. NADH-TR reaction disclosed more well-defined cores with loss of intermyofibrillary mitochondrial activity. These cores were usually located with loss of intermyofibrillary mitochondrial activity. These cores were usually located in the peripheral portions of the myofibers and the core size measured 10-30 microns in diameter. Electron microscopic examination revealed circumscribed areas of disintegrated Z band material and disorganized sarcomeric units near the sarcolemma. A decrease in the number of mitochondria and glycogen particles was noted.