Identification of malignant hyperthermia-susceptible ryanodine receptor type 1 gene (RYR1) mutations in a child who died in a car after exposure to a high environmental temperature.

Malignant hyperthermia (MH) is a genetic disorder of skeletal muscle in susceptible individuals that is triggered by exposure to anesthetic agents, and can cause death. Mutations in the ryanodine receptor type 1 gene (RYR1) are associated with MH-susceptibility. MH is also triggered in susceptible individuals by severe exercise in hot conditions or by overheating in infants. Here, we report a case of a child, 2years, 9months of age, who was left in a car and exposed to a high environmental temperature. The child was suspected to have died of heat stroke by autopsy examinations. Postmortem mutation analysis revealed that the child possessed two distinct RYR1 mutations. Since each mutation had previously been identified in a separate MH-susceptible patient, MH-susceptibility with over-response to the environmental high temperature might have occurred in this child with RYR1 mutations. These findings suggest that a MH-susceptible case may have died with a presumed diagnosis of heat stroke at autopsy.