HCM in Sphynx Cats
By Dr. Kevin Toman, DVM · Medically reviewed November 1, 2026 · 40+ years in clinical practice · 300+ cats with HCM treated
Short answer: Sphynx cats are among the breeds most prone to HCM, a disease that thickens the heart wall. Researchers have linked a change in a gene called ALMS1 to HCM in Sphynx. But that gene test is newer and less certain than the Maine Coon and Ragdoll tests. For a Sphynx, regular screening tests matter more than any DNA result.
Why Sphynx cats are at higher risk
HCM (hypertrophic cardiomyopathy) makes the heart's main pumping wall grow too thick and stiff. Any cat can get it. Sphynx cats get it more often than most breeds.
In one study of 55 Sphynx cats in New Zealand, 40% had HCM. Other studies have found high rates in Sphynx too, although the exact numbers vary by country and breeding line.
Sphynx cats can also be born with a heart valve problem called mitral valve dysplasia. It can look like HCM or occur alongside it. A heart ultrasound can tell them apart.
The Sphynx gene: ALMS1
The Maine Coon and Ragdoll mutations are in a gene called MYBPC3. The Sphynx variant is in a different gene, ALMS1. So Maine Coon and Ragdoll tests don't work for Sphynx.
In a 2021 study, researchers found the ALMS1 variant in 62 of 71 Sphynx cats with HCM.
Why the Sphynx gene test is less certain
This is the most important part of this article. The Sphynx test is not as well proven as the Maine Coon or Ragdoll tests.
| Question | What we know | Evidence |
|---|---|---|
| Is ALMS1 linked to HCM in Sphynx? | One US study found a strong link | Promising |
| Do all studies agree? | No. A New Zealand study found no link in its cats. | Unproven |
| How common is the variant? | Very common. More than half of Sphynx carry it in some groups. | Promising |
| How is it inherited? | Not settled. Likely recessive (two copies needed), but unclear. | Unproven |
| Do expert guidelines endorse it? | A 2024 review classed it as a variant of unknown significance | Unproven |
What this means for you:
- A positive result does not mean your cat will get HCM.
- A negative result does not mean your cat is safe.
- Breeders should not rely on this test alone. Heart ultrasounds of breeding cats are still the key tool.
From Dr. Kevin's 400+ Cats with HCM:
Sphynx cats are the SINGLE MOST common breed I see with HCM.
Because HCM can occur regardless of the gene test result, I believe the ONLY reason to run the gene test on a Sphynx is in a cat you are considering for breeding.
If they come back positive, PLEASE spay/neuter them for the good of the breed.
Want a screening test that counts? Have your vet do a Pro-BNP blood test once a year.
Symptoms to watch for
Early HCM often has no signs. When signs appear, they may include:
- A heart murmur or gallop sound your vet hears
- Less play or energy
- Faster breathing while asleep
- Breathing that looks like hard work
- Poor appetite
- Collapse
Many Sphynx cats have murmurs. Some are harmless, and some are not. Only an ultrasound can tell the difference. Some cats with HCM have no murmur at all.
Go to an emergency vet now for open-mouth breathing, struggling to breathe, collapse, or sudden back-leg weakness or pain.
How HCM is diagnosed in Sphynx cats
- Echocardiogram (heart ultrasound): the main test. It measures the heart wall and the left atrium, and it checks the valves.
- Blood pressure and thyroid tests: these rule out other causes of a thick heart.
- NT-proBNP blood test: good screening test.
- Gene test: optional extra information, but read the results with the limits above in mind.
When should a Sphynx be screened?
Because the gene test is uncertain, ultrasound screening is the backbone of Sphynx heart care.
- Breeding cats: a gene test before breeding, then an echo exam every year. A cardiologist is ideal.
- Pet Sphynx cats: A pro-BNP blood test at age 2, then every year after.
- Any Sphynx with a murmur, gallop or breathing change: get an ultrasound now.
- Before anesthesia: consider a heart check first, especially in older cats.
HCM can appear at any age. One normal scan does not mean lifelong protection.
Buying a Sphynx kitten? Ask the breeder
- Did both parents have heart ultrasounds? When, and by whom?
- Can I see the written ultrasound reports?
- Has any related cat had HCM, heart failure or sudden death?
- Were the parents gene-tested? (Useful, but not enough on its own.)
A breeder who screens with ultrasound every year is doing more than one who only gene-tests.
If your Sphynx has HCM
First, find the stage (A, B1, B2, C or D). The stage guides treatment and how often to recheck. The size and function of the left atrium matter most for the outlook. Learn about Stage B2 →
Treatment options may include:
- Clopidogrel to lower clot risk in higher-risk cats
- Felycin-CA1, a weekly sirolimus tablet. It was FDA conditionally approved in 2025 for cats with HCM and no symptoms. It targets the thickening itself. Learn more about Felycin here.
- Heart failure drugs if fluid builds up
Outside the US?
We ship Felycin routinely to the US, UK, and Canada. You start by sending your vet's prescription, or by enrolling your cat in our Cat Longevity Protocol. You can purchase Felycin from us and get guaranteed delivery, although it sometimes takes a few days.
If you live in the EU, Taiwan, Hong Kong, or China you can purchase Felycin from us. You start by enrolling your cat in our Cat Longevity Protocol. You provide the shipping, and we cannot guarantee delivery but we can absolutely send it your way.
Frequently asked questions
Are Sphynx cats prone to HCM?
Yes. Sphynx are among the breeds most likely to develop HCM.
Is there a genetic test for HCM in Sphynx cats?
Yes, for a variant in the ALMS1 gene. But studies disagree on how well it predicts HCM, so it should not replace heart ultrasounds.
Does the Maine Coon or Ragdoll test work for Sphynx?
No. Those tests look at a different gene (MYBPC3). Sphynx need their own test.
How often should my Sphynx have a heart ultrasound?
Often every 1 to 2 years for pets, and every year for breeding cats. Your vet will set the schedule.
Can a Sphynx with HCM live a long life?
Yes. Many stay stable for years. The outlook depends on the stage and whether problems develop.
Your next step.
Have questions about your Sphynx's heart? Enroll in our Cat Longevity Protocol now.
Free guide: HCM University · Related: HCM in Maine Coon Cats · HCM in Ragdoll Cats
References
- Meurs KM, et al. A deleterious mutation in the ALMS1 gene in a naturally occurring model of hypertrophic cardiomyopathy in the Sphynx cat. Orphanet J Rare Dis. 2021;16:108.
- Seo J, et al. ALMS1 variant and HCM in New Zealand Sphynx cats. 2024.
- Boeykens F, et al. Classification of feline cardiomyopathy-associated gene variants according to ACMG guidelines. 2024.
- Online Mendelian Inheritance in Animals. Cardiomyopathy, hypertrophic, ALMS1-related, in cats.
- Luis Fuentes V, et al. ACVIM consensus statement on cardiomyopathies in cats. J Vet Intern Med. 2020;34(3):1062–1077.
- US FDA. Conditional approval of Felycin-CA1. March 2025.
This article is for education only. It does not replace an exam, diagnosis or treatment plan from your own veterinarian. Prices and regulations change; confirm locally.