is a severe reaction to particular drugs used during surgery and other invasive procedures. People at increased risk for this disorder are said to have malignant hyperthermia susceptibility. If given these drugs, these people may experience muscle rigidity, breakdown of muscle fibers, a high fever, increased acid levels in the blood and other tissues, and a rapid heart rate. Without prompt treatment, the complications of malignant hyperthermia can be life-threatening. There are at least six forms of malignant hyperthermia susceptibility, which are associated with mutations in different genes (e.g., CACNA1S, RYR1). The susceptibility is inherited in an autosomal dominant fashion. People with certain inherited muscle diseases (e.g., central core disease and multiminicore disease) also have malignant hyperthermia susceptibility. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.