Most muscle diseases are hereditary and rare. Patients with a predisposition to Malignant Hyperthermia (MH), for instance, are in danger during anaesthesia with certain anaesthetics, due to the hereditary alteration of certain skeletal muscle proteins involved in skeletal muscle metabolism. MH reactions can be fatal if not treated rapidly and correctly. These patients do not normally have ailments in everyday life.
There are several muscle diseases, most of them progress slowly and may be present from infancy. The prognosis of such diseases varies greatly; the course of some muscle diseases is progressive, and the functional properties of the skeletal muscles is increasingly damaged. The function of the skeletal muscle of patients affected by Duchenne-Muscledystrophy is so damaged that they often die before the age of 25.