Suxamethonium spasm. A differential diagnostic conundrum.

Spasm of muscle in association with suxamethonium is not uncommon. As an accepted early sign of malignant hyperpyrexia (MH), patients have been referred for MH screening who have shown only this abnormality. Case histories of 277 probands have been analysed and grouped according to final diagnosis, depending on results of muscle biopsy and in vitro screening. When muscle spasm is induced with suxamethonium, malignant hyperpyrexia must be considered a probable diagnosis.