Diagnosis of susceptibility to malignant hyperthermia with flanking DNA markers

Objective - To define the region on human chromosome 19 carrying the gene for malignant hyperthermia susceptibility and to evaluate the use of flanking DNA markers in diagnosing susceptibility. Design - Prospective molecular genetic linkage studies in a large malignant hyperthermia pedigree. Setting - Irish malignant hyperthermia testing centre. Subjects - A large Irish malignant hyperthermia pedigree. Main outcome measures - Routine diagnosis of susceptibility to malignant hyperthermia with in vitro contracture test on muscle biopsy specimens and genetic linkage between susceptibility and polymorphic DNA markers in a malignant hyperthermia family. Results - Genetic typing of polymorphic DNA markers in a large Irish malignant hyperthermia pedigree generated a lod score of>3 for the marker D19S9 and showed that the gene for susceptibility is flanked by the markers D19S9 and D19S16. These tightly linked flanking markers allowed non-invasive presymptomatic diagnosis of susceptibility in five untested subjects in the large pedigree with an accuracy of >99·7%. Conclusions - DNA markers flanking the gene for susceptibility to malignant hyperthermia can be used with high accuracy to diagnose susceptibility in subjects in large known malignant hyperthermia pedigrees and may replace the previous in vitro contracture test for diagnosing this inherited disorder in large families with malignant hyperthermia.