Devon Rex Genetic Health Issues Explained: DNA Testing and Inherited Diseases

Devon Rex Genetic Health & Testing

Responsible Devon Rex breeders prioritize the health and prevention of inherited disease in their cats and kittens. Genetic testing and veterinary screenings help identify known genetic conditions, guide responsible breeding decisions, and provide peace of mind to families welcoming a kitten into their home.

While no test can guarantee a cat will never develop a health issue, careful and consistent testing significantly reduces preventable risks and supports the long-term health of the Devon Rex breed.

Genetic Conditions Covered in This Blog

This article provides an overview of the most relevant genetic health conditions and screenings in Devon Rex cats, including:

• Congenital Myasthenic Syndrome (CMS)

• Polycystic Kidney Disease (PKD)

• Hypertrophic Cardiomyopathy (HCM)

• Progressive Retinal Atrophy (PRA)

• Factor XII Deficiency (Hageman Trait)

• Blood Typing & Neonatal Isoerythrolysis (NI)

Each section explains what the condition is, how it is inherited, how breeders manage risk, and what it means for kitten buyers.

What This Means for Kitten Buyers

Genetic testing isn’t about creating “perfect” cats—it’s about stacking the odds in favor of health, transparency, and ethical breeding. Understanding what is tested, how conditions are inherited, and what testing can (and cannot) promise helps buyers make informed decisions.

This page explains what responsible breeders test for, why it matters, and what no test can promise—so buyers can make informed, confident decisions.

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Understanding Genetic Inheritance

When discussing genetic diseases, it’s important to understand how a condition is inherited, not just whether a test exists. Inheritance patterns explain how genes are passed from parents to offspring and whether a cat must inherit one or two copies of a mutation for a condition to develop.

Some conditions can remain hidden for generations, while others will appear every time an affected cat is bred. Knowing the inheritance pattern allows breeders to make ethical, informed decisions, prevent avoidable suffering, and protect the long-term health of the Devon Rex breed.

Common Inheritance Patterns in Cats

Autosomal Recessive

An autosomal recessive condition requires a cat to inherit two copies of a mutated gene—one from each parent—for the disease to be expressed.

• Cats with one copy are carriers and appear completely healthy

• Both males and females are affected equally

If two carriers are bred, each kitten has:

• 25% chance of being affected

• 50% chance of being a carrier

• 25% chance of being genetically clear

Because carriers look completely normal, autosomal recessive conditions can remain hidden in bloodlines for generations unless DNA testing is performed.

For buyers: When breeders test and avoid breeding two carriers together, affected kittens can be completely prevented.

Examples in Devon Rex: CMS, many forms of PRA

Autosomal Dominant

An autosomal dominant condition requires only one copy of the mutated gene to cause disease.

• Cats with the mutation will typically develop the condition

• There are no silent carriers

• Each kitten of an affected cat has roughly a 50% chance of inheriting the mutation

These conditions are easier to eliminate through responsible breeding—provided affected cats are not bred.

For buyers: A breeder who tests and removes affected cats from their program can eliminate these conditions entirely.

Example: PKD

Simple Mendelian Inheritance (Blood Type)

Some traits follow simple Mendelian inheritance, meaning they are controlled by a single gene with clear dominant and recessive forms.

In cats:

• Type A is dominant

• Type B is recessive

• Type AB results from specific gene interactions

Blood type itself does not cause disease, but mismatched breeding pairs can result in neonatal isoerythrolysis (NI)—a preventable and often fatal condition in newborn kittens.

For buyers: Blood typing is a behind-the-scenes safety measure that protects kittens in their first days of life.

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1. Congenital Myasthenic Syndrome (CMS)

Type: Neuromuscular genetic disorder

Test Available: Yes

Inheritance: Autosomal recessive

A mutation in the COLQ gene causes a congenital muscle weakness in Devon Rex and Sphynx cats, initially reported as “Spasticity.” CMS in cats is similar to congenital myasthenic syndrome in humans. Both males and females are equally affected, but cats with a single copy are carriers and show no symptoms.

Common Signs

• Generalized muscle weakness, especially after exercise, stress, or excitement

• Characteristic “dog-begging” or “chipmunk” posture with front legs resting on objects

• Signs may appear as early as 3 weeks of age and generally progress slowly

Outlook

• Moderate to severe cases may succumb by around two years due to choking or aspiration pneumonia

• Mild or static cases vary, but all affected cats require careful monitoring

  
  

Breeder Note

CMS is an autosomal recessive condition in which cats with one copy of the mutation are healthy carriers, while affected kittens can occur only if two carriers are bred together. Because carriers show no outward signs, DNA testing is essential, and responsible breeding practices can completely prevent the production of affected kittens.

What This Means for Buyers

CMS is a preventable condition when breeders use genetic testing responsibly. When breeders test their cats and avoid breeding two carriers together, kittens will not be affected by this disease.

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2. Polycystic Kidney Disease (PKD)

Type: Genetic kidney disorder

Test Available: Yes

Inheritance: Autosomal dominant

PKD in cats is caused by a mutation in the PKD1 gene, leading to the development of multiple kidney cysts. The heritable form typically presents early in both kidneys, often before 12 months of age, though renal failure usually occurs later.

Common Signs

• Early-onset, bilateral kidney cysts

• Multiple cysts detectable via ultrasound or genetic testing

• Progressive kidney dysfunction in adulthood

Outlook

• Progression varies; some cats live many years with monitoring and kidney-supportive care

• Chronic kidney disease may develop later in life

Breeder Note

PKD is an autosomal dominant disease, meaning cats that carry the mutation will typically develop the condition and pass it to approximately half of their offspring. Responsible breeders test for PKD and remove positive cats from breeding programs, allowing this disease to be eliminated from healthy lines.

What This Means for Buyers

PKD cannot be hidden, and testing protects kittens from developing kidney disease later in life. A breeder who tests and does not breed PKD-positive cats can prevent this condition entirely.

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3. Hypertrophic Cardiomyopathy (HCM)

Type: Heart disease (heart muscle thickening)

DNA Test: Limited — one known mutation primarily in Sphynx

Primary Screening: Echocardiogram with a cardiologist

Hypertrophic Cardiomyopathy (HCM) is the most common heart disease in cats and is often called a “silent killer,” as affected cats may show no symptoms until a sudden cardiac event occurs. HCM is most frequently diagnosed in young to middle-aged cats. While certain breeds may be predisposed, most cases have unknown or multifactorial causes.

Important: No breeder can guarantee a cat will never develop HCM. Screening reduces risk but does not eliminate it.

Many cats with mild HCM live full, happy lives. Awareness and routine veterinary care—not fear—are the most important tools for pet owners.

Possible Causes

• Genetic mutations: Certain mutations (documented mainly in Sphynx) can increase risk

• Polygenic inheritance: HCM in Devon Rex is likely influenced by multiple genes

• Environmental factors: Diet, obesity, and overall health may play a supporting role

• Unknown factors: Not all causes are fully understood; some cats develop HCM despite negative DNA results

Common Signs

• Rapid or heavy breathing at rest

• Lethargy or decreased activity

• Open-mouth breathing or distress

• Sudden collapse

• Sudden hind-leg paralysis from a blood clot

• Many cats show no symptoms until a serious event occurs.

Outlook

• Mild cases may live normal lives

• Moderate to severe cases may experience shortened lifespan or sudden cardiac events

Screening Methods

1. Genetic Testing

• Mutation in the myosin-binding protein C gene has been identified in Maine Coon, Ragdoll, and recently Sphynx.

• Cats inherit two copies of the gene:

  • Two normal copies: Low risk (but not zero; other mutations may exist)

  • One abnormal copy: Moderate risk

  • Two abnormal copies: Higher risk

Limitation: Only one gene is tested; a negative result does not guarantee the cat will remain free of HCM. There is still significant debate on the legitimacy and usefulness of this test. Even a cat with two abnormal copies may never develop HCM, so the results are not definitive. Currently, very few breeders of Sphynx—and even fewer Devon Rex—are doing the test. We aim to utilize every genetic test available here at Nightmagic Cattery, but we understand why not every breeder chooses to do so at this time.

2. Periodic Echocardiography

• Gold standard for detecting HCM in breeds without comprehensive genetic tests (e.g., Devon Rex, Sphynx).

• Cats should be at least 2 years old for screening to be valid.

• Recommended every 1–2 years for breeding cats.

• Even with regular scans, heart thickening can develop after a normal echocardiogram.

• Cost: $400–$1,000 per cat.

3. NT-proBNP Blood Test

• Measures a biomarker for heart strain

• Useful for ruling out disease when normal

• High false-positive rate; not diagnostic

Important Notes for Kitten Owners

• Heart murmurs in kittens are not always HCM

• Innocent murmurs are common during growth spurts and often resolve by 4–5 months

• Adult cats may develop temporary murmurs due to stress

• Always have murmurs rechecked before assuming disease

Breeder Note

HCM has a complex and likely polygenic inheritance in Devon Rex cats, and no single test can eliminate risk. Ethical breeders reduce risk through periodic echocardiograms, limited genetic testing where applicable, careful line tracking, and transparent disclosure, though HCM cannot be fully prevented.

What This Means for Buyers

HCM is not completely preventable, even with testing, and no breeder can guarantee a cat will never develop it. Many cats with mild HCM live long, happy lives with routine veterinary care, and screening helps identify issues earlier when management is possible.

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4. Progressive Retinal Atrophy (PRA)

Type: Genetic eye disorder

Test Available: Yes

Inheritance: Usually autosomal recessive

Progressive Retinal Atrophy (PRA) causes gradual degeneration of the retina, leading to vision loss and eventual blindness. Signs often appear in young adulthood.

Common Signs

• Night blindness or poor vision in low light

• Bumping into objects or walls

• Dilated pupils that do not respond normally to light

• Hesitancy in unfamiliar areas

• Gradual loss of vision over months to years

Outlook

• Progressive and irreversible, but cats often adapt well

• Lifespan usually not affected

Breeder Note

PRA is typically an autosomal recessive condition in which carriers show no symptoms but can produce affected kittens if bred together. DNA testing allows breeders to avoid these pairings and prevent affected kittens from being born.

What This Means for Buyers

PRA is a preventable condition through genetic testing. While it does not shorten lifespan, responsible breeding protects kittens and future generations from avoidable vision loss.

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5. Factor XII Deficiency (Variant 2)

Also known as: Hageman Trait

Type: Genetic blood clotting factor variant

Test Available: Yes

Inheritance: Autosomal recessive

Factor XII Deficiency is a blood factor variant that affects laboratory clotting test results but does not cause abnormal bleeding in cats. It is most often discovered incidentally during pre-surgical bloodwork when clotting times appear prolonged.

Importantly, this condition is considered clinically asymptomatic in cats. Cats with Factor XII Deficiency do not have an increased risk of bleeding during surgery or injury.

Common Signs

• None expected in daily life

• No increased tendency to bleed or bruise

• May show prolonged clotting times on laboratory screening tests (such as aPTT)

• Typically discovered incidentally during pre-surgical bloodwork

Outlook

• Excellent

• Cats with one or even two copies of this variant are typically clinically normal

• No impact on lifespan, quality of life, or activity level

• No treatment or management is required

Breeder Note

Factor XII Deficiency (Variant 2) is an autosomal recessive blood factor variant that does not cause illness or abnormal bleeding. Cats with one copy are carriers only, and even cats with two copies are typically clinically normal; this variant is tracked primarily for transparency and accurate interpretation of laboratory clotting results.

What This Means for Buyers

Factor XII Deficiency is not a disease and does not affect a cat’s health, lifespan, or bleeding ability. For pet owners, this result is informational only and does not require treatment or special care.

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6. Blood Typing

Type: Genetic test for blood group

Test Available: Yes

Inheritance: Simple Mendelian (Type A dominant, Type B recessive)

Blood typing determines a cat’s blood group (A, B, or AB). While it does not affect adult health, it is critical for preventing neonatal isoerythrolysis (NI) in kittens.

Common Signs of NI

• Weakness or lethargy in newborn kittens

• Pale or yellow gums

• Rapid breathing

• Death within the first few days of life (in severe cases)

Outlook:

• Blood type itself does not affect a cat’s health.

• Proper breeding and testing prevent NI in kittens.

Breeder Note

Blood type follows simple Mendelian inheritance. Responsible breeders blood type all breeding cats and manage pairings appropriately to prevent neonatal isoerythrolysis.

What This Means for Buyers

Blood typing protects kittens during their most vulnerable first days. While buyers may never see this process, it prevents a serious but entirely avoidable newborn condition.

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Recap

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Why Genetic Testing Matters

Genetic testing allows breeders to:

• Identify inherited diseases before symptoms appear

• Make informed, ethical breeding decisions

• Reduce carrier rates in the population

• Provide transparency and peace of mind to buyers

What Genetic Testing Does Not Mean

• It does not guarantee lifelong perfect health

• It does not replace routine veterinary care

• It does not eliminate all risk—only preventable risk

When combined with veterinary screening, testing greatly reduces avoidable disease and protects the integrity of the Devon Rex breed.

Costs of Genetic Testing in Devon Rex Cats

• Combination DNA panels: ~$100 per cat (covering CMS, PKD, PRA, coat genes, blood type)

• Echocardiograms: $400–$1,000 per cat for HCM screening

• Blood typing / individual tests: $20–$40 each, one-time test

Investing in testing and monitoring protects kittens and the breed, while being far more ethical and cost-effective than caring for affected cats or producing unhealthy litters.

Genetic testing is meant to prevent problems before they happen, not to diagnose disease in sick cats—a distinction that separates responsible breeding from damage control.

Important Note for Buyers:

Do not pay thousands of dollars for a kitten from a breeder who skips DNA testing.

A standard veterinary health exam is not a substitute for genetic testing. Responsible breeders invest in DNA panels and screenings to ensure the long-term health of their kittens and the breed.

If you’re up for Genetics Roulette, adopt a rescue Devon — the risks are the same, but you won’t be supporting an irresponsible breeder.

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Conclusion

Genetic testing, regular veterinary screening, and responsible breeding practices are essential to producing healthy, well-adjusted Devon Rex kittens. By understanding inheritance patterns and known genetic conditions, breeders and buyers alike can make informed decisions—ensuring a healthier future for this unique and deeply loved breed.