Screening of malignant hyperthermia susceptible families by creatine phosphokinase measurement and other clinical investigations.

We investigated 56 families afflicted with malignant hyperpyrexia. One hundred and twenty-four individuals within these families had had an episode of malignant hyperthermia, of whom we saw seventy-two. Serum creatine phosphokinase (CPK) was statistically higher in affected individuals and in close relatives than in normal volunteers. The magnitude of the serum CPK elevations varied significantly between families. While in some families the serum CPK was clearly elevated in affected individuals, in other families the serum CPK was normal or only moderately or inconsistently raised. In these latter families serum CPK measurement was therfore of little or no value in identifying afflicted members. The incidence of musculoskeletal abnormalities was greater in affected individuals and in close relatives than in the general population. Thus, the concomitant individual belonging to a family known to be susceptible to malignant hyperthermia was a better indicator of the MH trait than was the presence of only one of these parameters. For reasons which we do not fully understand, MHS individuals were found to require fewer anaesthetics than normal persons. The incidence of MH crises within each family fell significantly following investigation, counselling, and issuance of Medic-Alert bracelets.