Malignant hyperthermia susceptibility confirmed in both parents of probands. A report of three Austrian families.

From 1976 to 1986, 79 cases of suspected malignant hyperthermia (MH) were reported to the authors' institution. A total of 233 muscle biopsies was done in 66 families. The mother and father of the proband were investigated in 44 families; in three of these, both parents of probands gave positive test results. These three families, all from Vorarlberg, a secluded mountain area, represent 4.5% of all our MH-positive families (n = 61) and 7.3% of all MH-positive families where both parents had been tested (n = 41). This observation might be explained by: 1) a much higher incidence of MH in this part of Austria, and 2) a different test policy, as at the authors' institution, if possible, both parents are investigated, even if there is a positive test result in one of them. It is concluded that family investigations of MH susceptibility should always include both parents of a proband.