Malignant Hyperthermia in pigs, also called Porcine Stress Syndrome (PSS) is a hereditary disposition to increased stress sensitivity. This autosomal recessive trait is caused by a single base exchange within the ryanodine receptor gene (RYR1) and affects the calcium metabolism of muscle cells.
Due to the long-established selection of meaty, low-fat pork, the genetic defect has accumulated in many breeds because carriers of the gene have a higher meat and lower fat content. However, meat is often of inferior quality (PSE pork). In addition, exposition to severe stress (e.g. transportation, change of barn compartment, high temperatures, etc.) often leads to sudden death in PSS pigs or in less severe cases results in muscle cell damage caused by the accumulation of harmful metabolic products.
Genetic testing identifies PSS genotypes for selection of breeding animals.