Clinical reassessment of malignant hyperthermia in Abitibi-Temiscamingue

Purpose: In 1992, 1812 individuals (1.2% or the population) were labelled at risk for malignant hyperthermia (MH) in seven families from Abitibi-Temiscamingue; To evaluate the effective risk in this population, a multidisciplinary study was undertaken which included clinical, genealogical and molecular aspects, This paper presents the clinical aspects of the study. Method: For each of the 1546 individuals reached, ail anaesthetic exposures were screened For elements relevant to MH, Malignant hyperthermia events were analyzed with ''the clinical grading scale,'' All 44 reports of caffeine halothane contracture tests were reappraised, Finally, a genealogical study was done to complete each Family tree up to the initial French settlers in older to identify links between these seven families through common ancestors. Results: Following this reassessment, the families Were compared and classified into lour groups, Two families (1097 individuals) are not considered to be at a higher risk for MH than the population in general. Two families are still considered possibly at risk, Finally, one Family (402 individuals) is highly at risk and two other families are probably at risk, Family trees did not show any link up to the colonization of Abitibi-Temiscamingue in the beginning of this Century but common ancestors were round around the 9(th) generation. Conclusion: This clinical reassessment will help to focus education and prevention on a much smaller group of individuals still considered potentially at risk for MH, By adequate evaluation of phenotypes, combined with the use of a genealogical approach, it will be possible to target families For molecular research.