Myonecrosis due to Russell's viper bites in Sri Lanka.

Scattered or diffuse myonecrosis is the histopathologic basis for muscle pain and tenderness due to bites by Vipera russelli pulchella in Sri Lanka. These lesions may even occur without any clinical symptoms. Subclinical lesions may form one end of continuous spectrum, with the other being severe pain and muscle tenderness with rhabdomyolysis and myoglobinuria. Electromyographic abnormalities, when present, are suggestive of a myopathic pattern, rather than inflammatory muscle disease. A subclinical motor neuropathy may also occur. Hence, there is evidence for subclinical envenomation following bites by Russell's viper. Early antivenom therapy does not prevent the histologic, electromyographic, or nerve conduction abnormalities.