A possible genetic basis for false-positive halothane reactions in Australian pigs

Porcine malignant hyperthermia (MH) has been shown to be caused by homozygosity for a C to T mutation at position 1843 of the ryanodine receptor gene (Ryr1). It has also been concluded that this mutation was the sole cause of porcine MH. In this paper that conclusion is questioned. The incidence of Ryr1-1843-CC and CT halothane reactors (false positives) is reviewed and further cases of false-positive pigs from two Australian populations are presented. The familial nature of the cases in one of populations is investigated with the conclusion that porcine MH, like human MH, is likely to be heterogeneous.