American Shorthair vs Manx

The 'all-American working cat' story implies a hardy, mixed-heritage constitution, but this is a closed pedigree bred like any other purebred, and Cornell's feline health center lists American Shorthair among the breeds with an elevated rate of hypertrophic cardiomyopathy — the same silent heart disease people specifically worry about in Maine Coons.

The same gene that gives Manx cats no tail also frequently disrupts how the spinal cord forms — one cited study found spina bifida in 16% of Manx kittens — and cats that inherit two copies of the tailless gene die before birth, so every living Manx carries just one copy of a gene that, in its more severely affected individuals, causes lifelong hind-leg weakness and bowel or bladder incontinence.