Electron-microscopic study of systemic myonecrosis due to poisoning by tropical rattlesnake (Crotalus durissus terrificus) in humans.

: This article describes the ultrastructural study of skeletal muscle biopsy specimens from five patients following envenomization by tropical rattlesnake (Crotalus durissus terrificus). All the patients were bitten in the leg and the biopsy specimens were obtained from the contralateral gastrocnemius muscle in the middle of the lower leg. A wide spectrum of detailed ultrastructural changes involving muscle fibers and microvasculature was demonstrated. Essentially, such lesions included widespread necrotic myofibers intermixed with intact fibers, accompanied by changes in the endothelial lining of the intramuscular blood capillaries and small arterial vessels, reducing their lumens. Since these alterations were observed in biopsy specimens from the limb contralateral to the site of the bite, they clearly demonstrate the systemic myonecrotic action of the venom of a tropical rattlesnake. On the basis of these data, the mechanism of venom-induced myopathy is described. It is postulated that the pathogenesis of systemic myonecrosis due to poisoning by C durissus terrificus is a complex one, probably due to direct damage to cells by the myotoxins of the venom, as well as indirect effects due to ischemia.