Concurrence of malignant hyperthermia and congenital abnormalities. Two children about to undergo corrective surgery were required to be investigated for malignant hyperthermia (MH). These investigations arose out of concern by the anesthetist who had obtained a history of unexplained pyrexial reactions to anaesthetic in other members of the family. Because over the years we have encountered several children with multiple congenital abnormalities who have been found to be susceptible to MH, we stressed the advisability of biopsying not only the patient but also the patient's parents. Positive responses for MH were obtained in the patients and in one of the parents on each occasion. The hypothesis of intrauterine MH with its pharmacogenetic propensity for heat production is considered as a possible etiological factor which may cause abnormalities of a congenital nature. 