HCM in Sphynx Cats : A Closer Look at the Recent ALMS1 and HCM Study: Are We Missing the Full Picture?

There has been growing discussion among breeders about the ALMS1 gene and its connection to hypertrophic cardiomyopathy (HCM) in Sphynx cats. Some of that discussion has been helpful. Some of it has led to misunderstandings — particularly around what the most recent study actually shows and what conclusions can reasonably be drawn from it.

Let’s look at the data.

The study focused on a relatively small sample of 55 Sphynx cats. While the findings offer valuable insights, conclusions drawn from a sample this size should be viewed with caution. HCM is also an age-dependent disease — it may not fully develop during the study’s follow-up period of just under two years. Some cats that appeared unaffected at the time of assessment may develop HCM later in life.

Of the cats diagnosed with HCM in the study, 22.7% did not carry the ALMS1 variant, while 76.2% did — either homozygous (13.6%) or heterozygous (63.6%). Despite this, the researchers concluded that because the majority of the Sphynx population carries this mutation, the ALMS1 variant is likely not causative for HCM.

This conclusion deserves closer examination. The widespread prevalence of ALMS1 in the Sphynx population has been known for years — earlier studies had already documented this. What is new in this particular study is the decision to use that prevalence as a reason to dismiss the variant’s relevance to HCM entirely.

Following publication, some breeders began advising others to stop ALMS1 testing altogether, suggesting it is no longer necessary and that efforts should focus exclusively on heart scans and outcrossing. This interpretation moves beyond what the data supports. While not every cat with HCM carries the ALMS1 variant, a significant majority do. That alone does not prove causation — but it does not justify dismissal either.

No research has ever suggested that ALMS1 alone causes HCM. Genetic conditions like HCM are complex, influenced by multiple genes and environmental factors. The question is not whether ALMS1 is the sole cause — it almost certainly is not. The question is whether it plays a contributing role in a polygenic disease. Dropping it from testing panels based on one small study removes a data point without replacing it with anything better.

A broader perspective from recent research offers a useful counterpoint. A paper titled “Genetic Basis of Hypertrophic Cardiomyopathy in Cats” by Dr. Arkadiusz Grzeczka, Dr. Szymon Graczyk, Dr. Robert Pasławski, and Prof. Urszula Pasławska, published in Current Issues in Molecular Biology (August 2024), explores genetic mutations associated with HCM, with particular attention to ALMS1 in Sphynx cats.

According to Dr. Grzeczka, various mutations of the ALMS1 gene have been repeatedly linked to thickening of the left ventricular wall — a key feature of HCM. Homozygous ALMS1 mutations are found predominantly in Sphynx cats and similar breeds like Devon Rex. However, the gene’s widespread presence complicates straightforward interpretation. Dr. Grzeczka noted:

“Whether it’s worth testing for these mutations is difficult to answer, as they are widely spread in the cat population, which may indicate a predisposition to HCM in these cats.”

He also highlighted that ALMS1 mutations are found in humans, where they are sometimes linked to dilated cardiomyopathy — a condition more commonly diagnosed in dogs. This cross-species connection underscores the evolutionary importance of these mechanisms and their potential role in cardiac disease.

Prof. Pasławska offered further perspective on the value of continued testing:

“Nevertheless, I believe it is worth genetically testing cats and selecting those that are free from suspicious genes for breeding. Why the results in the New Zealand population turned out differently? I don’t know.”

This reflects an approach where the goal is not just to avoid problems now, but to prevent potential health issues in future generations. Combining genetic testing with regular heart scans provides a more complete strategy for managing HCM risk than relying on either method alone.

Ki-67 and HCM Management

In addition to ALMS1, Prof. Pasławska shared information about Ki-67, a nuclear protein linked to cell proliferation:

“Since it controls proliferation, it is a convenient marker for the intensity of cell growth. It has been shown that HCM is associated with increased cell growth. However, Ki-67 should not be regarded as a marker of hypertrophy, as its increase is also observed in cancer and during regenerative processes.”

She emphasised that elevated Ki-67 levels in HCM cases are an important marker for veterinarians, supporting the use of anti-proliferative therapies. Prof. Pasławska has used these therapies for six years with satisfactory results, though she cautioned that — like HCM itself — the therapy is not effective for every cat.

This is a developing area of veterinary cardiology. Ki-67 is not a diagnostic tool for HCM, but in cases where HCM is already confirmed, it may help guide treatment decisions. For breeders, the relevance is indirect but worth noting: HCM management is becoming more nuanced, and the more data points available — genetic, echocardiographic, and biomarker-based — the better the outcomes for individual cats.

Why This Matters for Breeding Decisions

HCM is a dominant genetic condition. Even one copy of a pathogenic variant can increase the risk of disease. Misrepresenting autosomal dominant mutations as harmless “carrier status” contradicts established genetics. This distinction matters — not as an academic point, but as a practical one that affects which cats enter breeding programmes and what information adopting families receive.

The argument that ALMS1 testing is unnecessary because the variant is widespread contains a logical gap: if three-quarters of affected cats carry the variant, removing it from testing panels means losing visibility of that data entirely. It doesn’t make the gene irrelevant — it makes breeders blind to it.

Our Position

We continue to test for the ALMS1 variant. Not because we believe it provides all the answers — it does not. But because its prevalence in affected cats suggests it remains a relevant factor in understanding HCM predisposition in the breed.

We combine genetic testing with annual echocardiographic screening and regular blood work including Troponin I and NT-proBNP Feline levels. These cardiac biomarkers support early detection and allow us to monitor heart health over time — not just at a single point.

All of our breeding cats are free from the ALMS1 mutation. That is not a guarantee against HCM — no single test can provide that. But it is one layer of protection in a strategy that prioritises having as much information as possible before making breeding decisions.

If the science evolves and demonstrates conclusively that ALMS1 plays no role in HCM, we will adjust. Until then, we see no reason to stop collecting data that may prove valuable — and every reason to continue.

Conclusion

Genetic testing for ALMS1 may not provide a complete answer to HCM in Sphynx cats. But both Dr. Grzeczka and Prof. Pasławska agree that genetic testing combined with cardiac imaging allows breeders to make more informed decisions and contributes to advancing research into feline health.

Dropping a test because one study questioned its relevance — based on 55 cats over less than two years — is not a scientific conclusion. It is a shortcut. And shortcuts in breeding have consequences that outlast the convenience they offer.