What HCM and PKD Testing Actually Rules Out

Look at ten Ragdoll cattery websites and you will see the same line on all ten: our cats are HCM and PKD tested. Ours says it too. It is a meaningful thing to say, but on its own it is close to useless to a buyer, because almost nobody explains what the tests do.

Here is the honest version, including the parts that are less reassuring.

HCM: the one that matters most in this breed

Hypertrophic cardiomyopathy is the most common heart disease in cats. The heart muscle thickens, the chamber cannot fill properly, and in bad cases it causes sudden cardiac death, sometimes in a young and apparently healthy cat.

Ragdolls have a breed-specific mutation associated with it, in a gene called MYBPC3. The Ragdoll version is known as R820W. Maine Coons have a different mutation in the same gene, called A31P, which is why a Maine Coon HCM test is not the same test.

The genetics work roughly like this. A cat can carry zero, one, or two copies. Cats with two copies are at high risk of developing serious HCM young, often between one and two years old. Cats with one copy frequently show no clinical signs and can live a normal lifespan. And the mutation shows incomplete penetrance, meaning some carriers never develop the disease at all.

What this means in practice for breeding is straightforward: never breed two carriers together, because that is how you produce a kitten with two copies.

Here is the part most websites leave out

A negative DNA test does not mean a cat cannot get HCM.

The test looks for one specific mutation. HCM still occurs in Ragdolls that do not carry R820W, which tells us there are other causes not yet identified. The testing laboratories say this themselves, plainly: a negative genetic result does not guarantee the cat will not develop some form of cardiomyopathy.

So the accurate claim is not "our kittens cannot get HCM." It is "our breeding cats do not carry the one Ragdoll mutation we currently know how to test for, so we are not knowingly passing it on." That is a real and worthwhile thing. It is just narrower than it sounds.

The other half of proper HCM screening is an echocardiogram performed by a veterinary cardiologist, which looks at the actual heart rather than the genes. Genetics tell you about risk inherited; an echo tells you about the heart as it exists today. They answer different questions, and neither replaces the other.

PKD: worth testing, less of a Ragdoll story

Polycystic kidney disease causes fluid-filled cysts to form in the kidneys, which grow slowly and can eventually cause kidney failure in middle age. The mutation is dominant, so a single copy is enough to cause it.

PKD is strongly associated with Persians and Persian-derived breeds. It is uncommon in Ragdolls. Because it can appear in lines that had outcrossing somewhere in their history, responsible breeders test anyway, but a Ragdoll breeder advertising PKD-clear cats is clearing a lower bar than the HCM test represents.

Unlike HCM, the PKD DNA test is fairly definitive for the mutation it targets. A clear cat will not pass on that particular version of the disease.

Blood typing: the one nobody mentions

This one rarely appears on breeder sites at all, and it should.

Cats have blood types A, B, and AB. If a type B queen is bred to a type A male, the resulting type A kittens can be poisoned by their own mother's first milk. The condition is called neonatal isoerythrolysis, and it can kill an entire litter in the first few days.

It is entirely preventable if you know the blood types in advance, which is why we blood type our queens. One of ours, Lovelit, is type B. Knowing that changes how she is bred and how her newborns are managed. A breeder who has never blood typed their cats is running a risk they do not know they are taking.

If you are evaluating breeders, this is a good question to ask precisely because it is not a standard talking point. The answer tells you whether someone is following a checklist or actually thinking.

Questions worth asking any breeder

• Can I see the actual test results for both parents? Not a statement on a website. The lab certificate, with the cat's registered name on it. Any breeder who tests will have these and will not mind sending them.
• Which HCM test did you run? If they cannot tell you it was the Ragdoll R820W test, be curious about why.
• Have your breeding cats had an echocardiogram, and when? A "no" is not disqualifying for a small cattery. A confused reaction to the question is more telling.
• Do you know your queens' blood types? See above.
• What exactly does your health guarantee cover? "Health guarantee" means whatever the contract says it means. Read it before the deposit, not at pickup.

What we do, and what we do not claim

Our breeding cats are genetically tested and blood typed, and we do not pair carriers. Every kitten leaves with a three-year genetic guarantee: if a kitten passes from a genetic disease within that window, we provide a replacement on receipt of a post-mortem report from a licensed veterinarian.

What we do not claim is that testing makes a kitten immune to anything. It does not. It means the known, testable risks have been checked and managed rather than ignored. Any breeder telling you their kittens are guaranteed healthy for life is telling you something that is not within their power to guarantee.

We also ask every buyer to have their kitten examined by their own vet within 72 hours of pickup. That is not a formality. It is an independent set of eyes, early enough to matter.

This article is general information about breed genetics, not veterinary advice. For anything concerning your own cat, talk to your veterinarian or a veterinary cardiologist.

Related reading: how to choose a Ragdoll breeder and Ragdoll colours and patterns explained.

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