Canadian Sphynx genetics

© Agnieszka Mianowska · Aggio Cat*PL · aggiocat.pl

From basic concepts to informed breeding decisions

Why is a Sphynx hairless even though it may carry a long-hair variant? How can healthy parents have an affected kitten? And why do some DNA tests help prevent disease while others fail to provide the answer breeders are hoping for? This short introduction to genetics explains what a cat inherits and what it can pass on to its offspring.

The basics: DNA, chromosomes, genes and alleles

DNA carries information about the structure and function of the body. In the cell nucleus, it is organised into chromosomes. A cat usually has 38 chromosomes, or 19 pairs: one set comes from its mother and the other from its father. A kitten therefore combines traits from both parents, although it need not look like either of them. [1]

A gene is a section of DNA containing specific information, for example the instructions needed to make a protein involved in hair structure. An allele is a version of a gene. For most genes discussed here, a cat has two alleles, one from each parent. A change in DNA is a mutation; not every mutation causes disease. Some affect appearance, while others have no noticeable effect.

Dominant means that one allele is enough for a trait to be expressed. Recessive means that an allele’s effect is expressed when it is not masked by a dominant allele; in a simple model, two copies of the recessive variant are needed. Dominance describes inheritance, not whether a trait is better, healthier or more common.

Having two identical alleles of a gene makes a cat homozygous, while two different alleles make it heterozygous. The genotype describes the cat’s genetic information, whereas the phenotype is its expressed traits, such as appearance. Both genes and the environment influence phenotype. Appearance alone therefore does not reveal everything a cat can pass on to its kittens.

What is visible, and what does a cat ‘carry’?

A black cat can carry chocolate. In a simplified example, the allele B produces black pigment, while b produces chocolate. A B/b cat looks black because B is dominant over b, but it can pass either allele to its offspring. When both black parents are B/b, each kitten has a 25% chance of B/B, a 50% chance of B/b and a 25% chance of b/b, which gives chocolate. This example leaves out other genes that modify colour. [2]

Could all the kittens in such a litter be chocolate? Yes, although this would be unlikely. The percentages apply to each kitten individually, not to a compulsory division within a litter. This illustrates the difference between a visible trait and a variant a cat ‘carries’. Detailed colour inheritance is, however, a separate and extensive subject.

Where did Sphynx hairlessness come from?

Canadian Sphynx hairlessness arose spontaneously as a natural mutation in domestic cats. Breeders established the trait and developed a breed around it. In 2010, Barbara Gandolfi and colleagues described a variant of the KRT71 gene associated with Sphynx hairlessness, and another variant of the same gene responsible for the Devon Rex’s curly coat. [3]

In traditional notation, the Sphynx variant is written as hr, and the Devon Rex variant as re. The normal-coat variant is dominant over both, while hr is dominant over re. A Sphynx can therefore be hr/hr or hr/re. Laboratories also use the symbols HR and DR, so always read the key accompanying the result. [4]

The table describes the inheritance of KRT71 variants, not a guaranteed litter composition or whether a mating is permitted under a breeding organisation’s rules. The degree of hair coverage varies among Sphynx cats; some have fine down.

How can a hairless cat carry long hair?

Hairlessness and hair length depend on different genes that affect different stages of coat development. KRT71 is involved in normal hair formation. In the Sphynx, its altered version disrupts this process: hairs have an abnormal structure and are easily lost. Hairlessness therefore does not mean a complete absence of hair follicles or that the cat produces no hair at all. [3]

By contrast, FGF5 affects how long hair grows. Variants associated with long hair extend this phase, allowing a longer coat to develop in a normally coated cat. They do not, however, remove the disruption caused by the KRT71 variant. Together, these genes explain why a Sphynx can have a genetic predisposition to long hair yet remain hairless: a longer growth period alone does not restore normal hair structure and retention. [3] [5]

When reading test results, it is useful to distinguish two situations. One copy of a recessive FGF5 variant means carrier status; even a normally coated cat remains short-haired in this case. Two long-hair alleles, one from each parent, usually produce long hair unless another trait, such as hairlessness, interferes with coat formation. A Sphynx can therefore carry and pass on genetic information for hair length without showing it. FGF5 results must be interpreted alongside KRT71 results. ‘Carries long hair’ does not mean that the cat will grow a long coat over time. [5]

Breed development and CMS: what did early outcrosses introduce?

At the beginning of the breed’s development, hairless cats were scarce. To expand the gene pool and maintain breeding continuity, they were also mated to other cats, particularly Devon Rex cats. Alongside greater diversity, however, disease-causing variants could also enter the breed.

One example is congenital myasthenic syndrome (CMS), a neuromuscular disease previously known in Devon Rex cats. It causes muscle weakness, rapid fatigue and, in some cats, difficulty swallowing. The same disease-causing variant of the COLQ gene was found in both breeds. Pedigree analyses reported in a 2015 study support the explanation that it entered the Sphynx population through early matings with Devon Rex cats. It is not a consequence of hairlessness itself. [6]

A healthy appearance could not identify a carrier. A DNA test for this form of CMS became available only in 2015, many years after those outcrosses. Today, the variant can be detected before breeding and parents selected accordingly. [7]

CMS is recessively inherited: a cat with one copy is a healthy carrier, while two copies cause disease. Mating two carriers gives each kitten a 25% risk of being affected. A carrier mated to a cat clear of the variant should not produce kittens affected by this form of CMS, although each kitten has a 50% chance of being a carrier. A carrier therefore need not automatically be excluded from breeding: appropriate mate selection and testing of offspring can protect health while preserving genetic diversity. [8]

© Agnieszka Mianowska · Aggio Cat*PL · aggiocat.pl

PKD: why test for diseases associated with another breed?

Polycystic kidney disease (PKD) is particularly well known in Persians and related breeds. Cysts developing in the kidneys can eventually lead to kidney failure. In 2024, Joanna Nowacka-Woszuk and colleagues reported the same pathogenic PKD1 variant in Sphynx cats that had previously been associated with disease in Persians. Fourteen cats from two related families were examined; both cysts and the variant were found in seven. [9]

One possible explanation is historical outcrossing to Persians or breeds with Persian ancestry. I know of cases in which Sphynx cats were crossed with Persians to produce a shorter profile. This makes such matings a plausible route for introducing PKD1, but does not prove that this is how the variant reached the cats in the study. I do not know the test results or complete history of all such matings.

UC Davis also notes that inherited PKD1 need not have originated as a new mutation in Persians: the variant may previously have occurred in non-pedigree cats. Finding the same change in Sphynx cats therefore cannot, on its own, reconstruct its route into the breed. The variant’s presence in Sphynx cats is confirmed, but its precise origin remains unknown. Outcrossing to Persians is a possible explanation, not a settled account of its history. [10]

The practical conclusion is important: a test should not be overlooked simply because the disease is mainly associated with another breed. The PKD1 variant is dominant, so one copy is sufficient to cause this form of the disease. A cat may not yet show visible signs, but it is not a healthy carrier in the sense described for CMS. It should not be bred. DNA testing detects the variant, while ultrasound shows the condition of the kidneys; the tests complement one another. [10]

HCM and ALMS1: great hopes and later reassessment

Hypertrophic cardiomyopathy (HCM) is a heart muscle disease involving abnormal thickening. Researchers have spent years looking for genetic changes in Sphynx cats that could help reduce disease in future generations. One such hope came from the work of a team led by Dr Kathryn Meurs at North Carolina State University, concerning a variant of the ALMS1 gene. The scientific paper was published on 27 February 2021. [11]

News of the discovery reached breeders in 2020, after around ten years of research. Dr Meurs presented the ALMS1 variant as a possible explanation for around 60% of HCM cases in Sphynx cats. She also described the discovery in these terms during a webinar I attended. The long search and the finding of a variant in around 60% of affected Sphynx cats were also reported in TICA’s January 2021 newsletter. For us as breeders, this brought enormous hope: it seemed that we would finally have a tool to identify some risks before changes developed in the heart. Selecting parents appropriately was expected to help reduce HCM in subsequent generations. This was the promise associated with the introduction of the ALMS1 test. [12]

Later studies did not confirm the variant’s expected usefulness. A 2024 study in New Zealand, involving 55 Sphynx cats, found no association between ALMS1 and an HCM diagnosis. A similar result was obtained in Thailand in 2026 in a group of 47 Sphynx cats. The studies had limitations, including small groups and, in Thailand, the young age of most cats. They do not explain all the genetics of HCM, but provide no basis for treating ALMS1 as a reliable predictive test for the disease. [13] [14]

The test detects a specific variant, not the presence or absence of the entire ALMS1 gene. Sphynx breeders still lack a validated DNA test that would allow breeding pairs to be selected so as to reduce HCM effectively within the breed. This does not mean that the disease has no inherited basis; its genetic causes remain insufficiently understood. Requiring an ALMS1 result as a guarantee that a kitten will not become ill is therefore unjustified. The result does not replace heart screening. [13] [14]

What does an echocardiogram show?

The basis of monitoring remains regular echocardiography, performed by a veterinarian with cardiology experience. It can detect changes before symptoms appear and shows the heart’s structure and function on the examination day. A normal result does not exclude future HCM, so screening cannot stop after one good result. Successive test results and the health of the cat’s relatives also matter when planning breeding. [13] [15]

HCM must also be distinguished from heart muscle thickening caused by other conditions, such as hypertension or hyperthyroidism. Age alone or a single echocardiogram cannot establish an inherited cause; veterinary assessment and other findings are needed. [15]

Blood groups: important before mating

The main feline blood group system includes A, B and AB, whose inheritance is associated with variants of the CMAH gene. Blood group B is neither a disease nor a defect. A risk may arise when a type B female gives birth to type A or AB kittens. Antibodies absorbed from her colostrum can destroy the kittens’ red blood cells. This is neonatal isoerythrolysis, a life-threatening condition.

Knowing the parents’ blood groups makes it possible to assess the risk before mating and agree a management plan with the veterinarian in advance. DNA testing helps predict inheritance but covers specific variants. Direct blood typing may be needed to confirm the result. [16]

How do I use this knowledge at Aggio Cat*PL?

At Aggio Cat*PL, we test all our cats with the full Wisdom Panel / MyCatDNA feline genetic panel. The results help us check known inherited disease variants, blood groups and traits that may be passed to offspring. MyCatDNA is designed for breeders and also includes information about genetic diversity. [17]

A ‘full panel’ means the complete scope of that particular product, not testing for every possible feline disease. A ‘clear’ result applies to the specific variant tested. We therefore combine DNA results with pedigree analysis, information about relatives’ health and clinical examinations. Our breeding cats have an echocardiogram before their first mating, then annually, or more often when indicated.

Testing before breeding matters beyond a single litter: it helps reduce the transmission of known pathogenic variants to future generations. The history of CMS shows what a useful test and informed mate selection can achieve. The ALMS1 story reminds us that a test’s availability alone does not establish its value for breeding.

© Agnieszka Mianowska · Aggio Cat*PL · aggiocat.pl

Sources and literature

Verified as of 27 October 2026. Scientific publications and research institution resources; the TICA newsletter is a historical source for the announcement of the ALMS1 discovery, not for the current assessment of the test.

1. University of Missouri, Feline Genetics Laboratory. Cat Genomic Resources: Karyotypes. Feline chromosome count.
2. UC Davis, Veterinary Genetics Laboratory. Brown (Chocolate and Cinnamon). B and b alleles and chocolate inheritance.
3. Gandolfi B. et al. (2010). The naked truth: Sphynx and Devon Rex cat breed mutations in KRT71. Mammalian Genome, 21, 509-515.
4. UC Davis, Veterinary Genetics Laboratory. Sphynx and Devon Rex Coats. Inheritance of hairlessness and curly coats.
5. UC Davis, Veterinary Genetics Laboratory. Long Hair. Kehler J.S. et al. (2007). Four Independent Mutations in the Feline Fibroblast Growth Factor 5 Gene Determine the Long-Haired Phenotype in Domestic Cats. Journal of Heredity, 98(6), 555-566.
6. Abitbol M. et al. (2015). A COLQ Missense Mutation in Sphynx and Devon Rex Cats with Congenital Myasthenic Syndrome. PLOS ONE, 10(9), e0137019.
7. UC San Diego, Comparative Neuromuscular Laboratory (2015). Genetic Testing Now Available at University of California Davis and University of Milan for Inherited Myopathy in Sphynx and Devon Rex Cats.
8. UC Davis, Veterinary Genetics Laboratory. Sphynx and Devon Rex Congenital Myasthenic Syndrome (CMS).
9. Nowacka-Woszuk J. et al. (2024). First report on the presence of a common pathogenic variant in the PKD1 gene, causing polycystic kidney disease, in a series of related Sphynx cats. Topics in Companion Animal Medicine, 63, 100928.
10. UC Davis, Veterinary Genetics Laboratory. Polycystic Kidney Disease (PKD1). Inheritance, interpretation of results and possible origin of the variant.
11. Meurs K.M. et al. (2021). A deleterious mutation in the ALMS1 gene in a naturally occurring model of hypertrophic cardiomyopathy in the Sphynx cat. Orphanet Journal of Rare Diseases, 16, 108.
12. The International Cat Association (13 January 2021). TICA January 2021 Newsletter, reporting the discovery by Dr Kathryn Meurs’s team: more than a decade of research and a variant detected in around 60% of Sphynx cats with HCM.
13. Seo J. et al. (2024). Prevalence of Hypertrophic Cardiomyopathy and ALMS1 Variant in Sphynx Cats in New Zealand. Animals, 14(18), 2629.
14. Sussadee M. et al. (2026). Prevalence and Clinical Relevance of Alström Syndrome Protein 1 Gene Variant and Feline Hypertrophic Cardiomyopathy in Sphynx Cats in Thailand. Animals, 16(12), 1815.
15. Luis Fuentes V. et al. (2020). ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. Journal of Veterinary Internal Medicine, 34, 1062-1077. Kittleson M.D., Meurs K.M., Harris S.P. (2015). The genetic basis of hypertrophic cardiomyopathy in cats and humans. Journal of Veterinary Cardiology, 17, S53-S73.
16. UC Davis, Veterinary Genetics Laboratory. AB Blood Group in Domestic Cat Breeds. Blood group inheritance and test limitations.
17. Wisdom / MyCatDNA. MyCatDNA panel description and FAQ. Product scope and use in breeding.

In preparing the introduction, I drew on Anna Wilczek’s presentation ‘Genetyka dla Humanistów, czyli co po kim i dlaczego w ćwiczeniach praktycznych’ (‘Genetics for Humanists: Who Inherits What and Why, Through Practical Exercises’). I also describe my own breeding practice and Dr Meurs’s 2020 webinar, which I attended. The information about outcrossing to shorten the profile is based on breeding cases known to me.

© Agnieszka Mianowska · Aggio Cat*PL · aggiocat.pl