Förekomst av MyBP-C mutationer hos katter med hypertrofisk kardiomyopati

Sammanfattning: Hypertrophic cardiomyopathy (HCM) is the most commonly diagnosed cardiac disease in cats. The phenotype varies from mild focal thickening to severe concentric hypertrophy at the left ventricle. Two separate myosin binding protein C (MYBPC3) mutations have been identified in Maine coon cats (A31P and A74T) and one in Ragdoll cats. All three of them seem to cause familial HCM in an autosomal dominant pattern. The purpose of this study was to investigate the presence of these three mutations in population cats of different breeds with HCM in Sweden. The results may show if HCM is present in the absence of these mutations. Thus, the value of genetic tests to identify HCM will be evaluated. Blood samples were collected from 21 cats (8 different breeds), diagnosed by echocardiography, with focal or concentric hypertrophy ≥6 mm of the left ventricle. Two out of four Maine coon cats were homozygous for the A31P mutation but all other cats were negative for that mutation. The "Ragdoll mutation" was identified in the only Ragdoll cat in our study, and the A74T mutation in eight of the cats (different breeds). One of these eight cats were homozygous and seven heterozygous. The presence of the A74T mutation has not yet been established in three of the cats. The presence of the A31P and "Ragdoll" mutation is consistent with previous published studies concerning Maine Coon and Ragdoll cats. For that reason it may be valuable to analyse Swedish Maine Coon and Ragdoll cats for respective mutation. The fact that the A74T mutation was identified in 44 % of the cats can be due to a dissemination of a pathological mutation into several breeds, but more likely, it may be a non pathological variation in the genome, so called polymorphism. The cats that were negative for all three mutations could have myocardial hypertrophy secondary to other disease, or another, so far unknown, mutation causing HCM. Since most of the cats have moderate to severe changes, and no other known disease that could have caused the hypertrophy, the last alternative is most likely. It is concluded that the genetic tests of today are not reliable in ruling out HCM in cats of different breeds. They may, however, be useful for guidance when breeding with Maine coon and Ragdoll. Echocardiographic screening for HCM is obviously necessary in the future to rule out HCM.