I had 3 purebreed Devon Rexes. One died of a sudden heart failure, due to undiagnosed HCM, one has kidney problems and will be on special diet for the rest of his life and third has intestine problems, so that food doesn’t absorb properly. We feed him douple dose of best high meat content cat food we can find and he just barely keeps his minimum weight.

So yeah purebreeds have problems.