This autosomal recessive disease occurs in many breeds of pigs, predominantly in lean but heavily muscled breeds. The disease is caused by a mutation of the ryanodine receptor in the skeletal muscle. The regulation dysfunction of the Ca²+ ions result in a reduced threshold of muscular contraction. Hypermetabolism and hyperthermia are attributable to inhalation anaesthesia, muscle relaxants and stress, tissue damage of the liver, kidney and nerves result.