[Clinical and ultrastructural studies on 8 cases of methamidophos toxicologic myopathy]

Clinically, there was pain or numbness in the lower limbs at first; then followed by muscular weakness and symmetrical wasting of the small muscles of the hands and lower limbs. Electromyography showed myogenic changes in all the 8 cases and biopsies indicated atrophy of muscle fibers. The most prominent ultrastructural change was presence of abnormal accumulation of myofibers with regeneration and necrosis. There was decrease of mitochondria and glycogen even disappearance of M--line or Z--line. The pathogenesis is considered due to cell--mediated--immunity and direct toxic effect.