First described in 1956, central core disease is a slowly progressive disease of voluntary muscle, or those necessary for movement. It is disabling but not life-threatening. It normally affects the hips and legs, although it can eventually involve most of the body's voluntary muscles.
People who have central core disease are sometimes susceptible to malignant hyperthermia, a condition brought on by anaesthesia during surgery. Malignant hyperthermia causes a rapid, and occasionally fatal, rise in body temperature and produces muscle stiffness.