A family with discordance between malignant hyperthermia susceptibility and rippling muscle disease.

Rippling muscle disease (RMD) is a disorder that affects striated muscle and involves disturbances in calcium homeostasis. Malignant hyperthermia susceptibility (MHS) is a potentially lethal disorder, characterized by extreme hypermetabolism and muscle rigidity/rhabdomyolysis during anesthesia with potent inhalational agents, in otherwise healthy individuals. The aim of this report was to search for a correlation between RMD and MHS in members of a family in which both disorders were present. Ten members of a large Swedish family segregating RMD were tested for MHS prior to establishing an RMD diagnosis. Results from diagnostic RMD investigations and anesthesia outcomes were collected and cross-referenced to evaluate whether phenotype variations could be predicted by in vitro contracture test (IVCT) results suggestive of MHS. No correlation was found between individual RMD phenotypes and the IVCT results. There were no recorded adverse reactions to anesthesia, and RMD and MHS did not co-segregate. We conclude that RMD patients should not, on the basis of our present knowledge, be classified as having MHS; however, an increased surveillance for MH reactions is recommended in these patients.