# Polydactyl Gene in Cats: How Extra Toes Happen

The polydactyl gene in cats is a dominant genetic trait that causes one or more extra toes, usually on the front paws. A kitten only needs to inherit the gene from one parent to show extra digits. Most polydactyl cats live normal, healthy lives, but the extra toes do need regular checking.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

## Quick Answer

- Polydactyly means extra digits, and in cats it is usually a harmless, non-syndromic trait that does not affect limb function [1][2].
- The trait is dominant, so one copy of the gene from either parent is enough for a kitten to be born with extra toes [2].
- Most extra toes appear on the front paws on the inner (preaxial) side, though rear paws and mixed patterns happen too [1][3].
- The main health risk is nail overgrowth and injury to the extra digit, not the extra toe itself [1].
- Any cat with extra toes should have those nails trimmed on a regular schedule and checked at routine exams.

## What the Polydactyl Gene Actually Does

Polydactyly is the presence of one or more extra digits that may not be anatomically normal [1]. In cats, the extra toes usually sit on the medial (inner) side of the limb, which veterinarians call preaxial polydactyly [1]. Postaxial polydactyly, where the extra digit is on the outer side, is less common in cats [1].

The gene itself does not code for "toes." It sits in a regulatory region called the ZRS, which controls a limb-development gene named Sonic hedgehog (Shh) [4]. When the ZRS sequence is altered, Shh gets switched on in the wrong place and at the wrong time during limb formation, and the result is extra digits [4]. This same ZRS region is linked to polydactyly in humans, cats, and mice, so the basic mechanism is shared across species [4].

In cats, researchers have identified at least three variants in this regulatory sequence. Two were found in outbred domestic cats in the UK, and one, called the Hw variant, was found in Hemingway cats in the USA [2]. The Hw allele has also been identified in a subset of polydactyl Maine Coon cats [2]. So the polydactyl trait in cats is not one single mutation. It is a family of mutations in the same control region, which is why different cats can have different toe patterns.

## How Do Cats Get Extra Toes? The Inheritance Pattern

Polydactyly in cats is inherited as a dominant trait [2]. That means a cat only needs one copy of the variant to have extra toes. If a polydactyl cat is bred to a non-polydactyl cat, roughly half the kittens would be expected to inherit the trait, though the exact outcome depends on the parents' genetics.

Because it is dominant, you can see polydactyly in cats with no breed at all. It shows up in outbred domestic cats, in Maine Coons, and in Pixie Bobs [2]. A cat does not need two polydactyl parents to pass the trait on.

The trait also varies a lot in how it looks. In a study of 70 Maine Coon cats, including 48 polydactyl cats from four breeding lines, the physical expression ranged widely. Cats differed in how many extra digits they had, how those digits were shaped, and even in the structure of the carpus (wrist) and tarsus (ankle) [3]. Some cats had one extra toe. Others had several. Some extra digits were fully formed with bone and claw, and some were small and attached by soft tissue only.

One reassuring finding from that same study: when researchers compared the radius (a forearm bone) in polydactyl and non-polydactyl kittens and adult females, they found no size difference between the two groups [3]. The extra toes did not come with a smaller or weaker limb.

## A Step-by-Step Plan for Owners of Polydactyl Cats

If your cat has extra toes, here is a practical routine you can follow.

### Step 1: Count and map the toes at home

Pick a calm moment and look at each paw. Count every digit, including the extra ones. Note which paw has extras and whether the extra toe has a claw. Write it down or photograph each paw. This baseline helps your veterinarian spot changes later.

### Step 2: Learn where the extra nails sit

Extra digits often sit tucked against the inner side of the paw, sometimes higher up the leg. These nails may not touch the ground, so they do not wear down naturally. That is the single biggest reason polydactyl cats need nail care.

### Step 3: Trim nails on a schedule

Ask your veterinarian or a veterinary technician to show you how to trim the extra nails safely the first time. After that, check them every two to four weeks. If you are not comfortable trimming, book nail trims with your vet or a groomer. Overgrown nails can curl into the paw pad and cause pain or infection.

### Step 4: Check the extra toes at every home exam

Once a week, run your fingers over each extra digit. Feel for swelling, heat, redness, discharge, or a nail that has grown into the skin. Look between the toes for mats of hair or debris that can trap moisture.

### Step 5: Keep routine veterinary visits

Bring your cat in for a normal wellness exam at least once a year, or more often for seniors. Point out the extra toes so your veterinarian examines them along with the rest of the limbs. If your cat also has eye or ear issues, those deserve their own evaluation. Two related reads are [Cat Third Eyelid Protrusion](/knowledge/veterinary-medicine/clinical-methods/cat-third-eyelid-protrusion) and [Ear Polyps in Cats: Signs, Diagnosis, Surgery, and Recurrence](/knowledge/veterinary-medicine/clinical-methods/ear-polyps-in-cats).

### Step 6: Watch for breed-related conditions separately

Polydactyly itself is not linked to kidney disease, skin fungus, or eye problems. If you own a Persian or a related breed, screening for other inherited conditions is a separate conversation. See [Polycystic Kidney Disease PKD in Persian Cats: Screening and Treatment](/knowledge/veterinary-medicine/urology-nephrology/polycystic-kidney-disease-pkd-in-persian-cats-screening-and-treatment) for that topic.

## Polydactyly Cats Genetics: What to Expect at Each Life Stage

| Life stage | What to check | How often |
|---|---|---|
| Kitten (under 6 months) | Count toes, confirm all nails present, watch for nail snags during play | Weekly |
| Young adult (6 months to 7 years) | Trim all nails including extras, check for ingrown nails | Every 2 to 4 weeks |
| Senior (7 years and up) | Full paw exam, watch for arthritis or nail changes, wellness bloodwork | Every 6 to 12 months |
| Any age after injury | Check the extra digit for cuts, swelling, or infection | Same day if injured |

The extra digit is the part most likely to need attention over a cat's life. In dogs and cats, preaxial polydactyl digits are typically not clinically relevant to limb function unless the extra digits become damaged or infected, and problematic digits often require amputation [1]. That is the scenario to prevent with good nail care and quick attention to injuries.

## Signs That Something Is Wrong With an Extra Toe

Most polydactyl cats never have a problem. When issues do arise, they usually involve the extra digit itself.

Watch for these signs:

- A nail curling into the paw pad or the side of the toe
- Swelling, redness, or warmth around one digit
- Limping, hopping, or refusing to bear weight on one paw
- Licking or chewing at one specific toe
- Discharge, bleeding, or a bad smell from the nail bed
- A nail that has torn or snagged on carpet, bedding, or a scratching post
- A digit that suddenly looks bent or angled differently than before

Any of these can point to infection, injury, or an ingrown nail. Your veterinarian can examine the digit, clean it, trim the nail, and decide whether treatment or removal is needed. Problematic digits often require amputation [1], but that decision is made case by case after an exam.

## Common Mistakes Owners Make With Polydactyl Cats

**Skipping the extra nails.** This is the most common mistake. Extra nails that do not touch the floor keep growing. They can curve back into the pad and cause pain.

**Assuming extra toes mean other health problems.** Polydactyly in cats is generally a non-syndromic preaxial polydactyly, meaning it appears on its own without a cluster of other defects [2]. It does not automatically mean your cat has a systemic disease.

**Breeding without thinking about genetics.** Because the trait is dominant, a polydactyl cat can pass it to kittens even when the other parent has normal paws [2]. If you breed cats, talk with a veterinarian about genetic testing before planning a litter.

**Confusing polydactyly with a dewclaw.** Cats normally have a dewclaw higher on the inner front leg. An extra toe from polydactyly is a separate digit, and it may or may not have a full claw and bone.

**Ignoring paw structure differences.** Polydactyly in Maine Coons affects not only digit number and conformation but also carpus and tarsus conformation [3]. If your cat's gait ever changes, mention the paw structure to your vet.

**Waiting on an injured toe.** A torn nail or infected digit can worsen quickly. Call your veterinarian the same day you notice it.

## Supplies and Home Setup That Help

A few simple items make polydactyl paw care easier.

- **Cat-specific nail clippers.** Human clippers can split the nail. Ask your vet which style they recommend for thick or curved nails.
- **Styptic powder.** Keep it on hand in case you nick the quick while trimming.
- **A bright light or headlamp.** Extra toes sit in shadowed spots, so good lighting helps you see the nail and the pad.
- **A nonslip mat.** If your cat has unusual paw conformation, a mat near food and litter boxes can add traction.
- **A paw journal.** Track nail trim dates and any changes in each extra digit. Bring it to appointments.
- **A treat jar.** Pair every paw handling session with a treat so your cat tolerates exams without stress.

If your cat has other skin or coat concerns, such as circular patches of hair loss, that is a different problem. See [Ringworm In Cats](/knowledge/veterinary-medicine/parasitic-diseases/ringworm-in-cats) for that topic.

## Limitations and When to Contact a Veterinarian

Polydactyly research in cats is still developing. The ZRS variants explain many cases, but the full picture of feline polydactyly genetics is not completely settled, and some inheritance patterns remain unclear [2][5]. Not every polydactyl cat will fit a neat genetic category. Your veterinarian evaluates your individual cat, not a general rule.

Contact your veterinarian the same day if you see:

- A nail growing into the paw pad
- Swelling, redness, or discharge around an extra toe
- Limping that started suddenly
- Bleeding from a nail or toe
- Your cat licking one paw constantly

Go to an emergency clinic now if:

- Bleeding will not stop after a few minutes of pressure
- A toe looks bent at an unnatural angle after a fall or jump
- Your cat cannot put any weight on the leg at all
- The paw is swollen, hot, and your cat cries when you touch it

Schedule a routine visit if:

- You just adopted a polydactyl cat and want a baseline paw exam
- You are unsure how to trim the extra nails
- You notice a gradual change in how your cat walks
- You want to discuss breeding or genetic testing

Individual cases need a veterinarian who can examine your cat in person. No article can replace that exam.

## Frequently Asked Questions

### Do polydactyl cats have more health problems?

Most polydactyl cats are healthy and have no extra health problems beyond the extra toes themselves. Preaxial polydactyl digits are typically not clinically relevant to limb function unless they become damaged or infected [1]. The main ongoing task is nail care and watching for injury.

### Is polydactyly in cats dominant or recessive?

It is dominant. A cat needs only one copy of the variant to have extra toes, which is why the trait appears in outbred cats, Maine Coons, and Pixie Bobs [2]. A polydactyl cat bred to a normal cat can still produce polydactyl kittens.

### Can a cat have extra toes on the back paws only?

Yes, though front paw involvement is more common. Polydactyly can appear on the medial or lateral side of a limb, and the pattern varies between cats [1]. In one case report, a cat had extra digits on both the front and rear limbs [6].

### Will my polydactyl cat need surgery?

Most polydactyl cats never need surgery. Surgery is considered only when an extra digit is damaged, infected, or causing problems, and problematic digits often require amputation [1]. Your veterinarian decides based on the exam and the specific digit.

### Does polydactyly affect how long a cat lives?

There is no evidence that polydactyly shortens a cat's lifespan. The trait affects limb development, not overall organ function [1][3]. Lifespan depends on routine care, diet, indoor safety, and regular veterinary checkups.

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## Related Articles

- [Ear Polyps in Cats: Signs, Diagnosis, Surgery, and Recurrence](/knowledge/veterinary-medicine/clinical-methods/ear-polyps-in-cats)
- [Cat Third Eyelid Protrusion](/knowledge/veterinary-medicine/clinical-methods/cat-third-eyelid-protrusion)
- [Cat Third Eyelid Showing Why](/knowledge/veterinary-medicine/clinical-methods/cat-third-eyelid-showing-why)
- [Polycystic Kidney Disease PKD in Persian Cats: Screening and Treatment](/knowledge/veterinary-medicine/urology-nephrology/polycystic-kidney-disease-pkd-in-persian-cats-screening-and-treatment)
- [Ringworm In Cats](/knowledge/veterinary-medicine/parasitic-diseases/ringworm-in-cats)
- [Calico Cat: Fascinating Facts and Genetics Explained](/knowledge/veterinary-medicine/symptom-guides/calico-cat-facts-genetics)
- [Polydactyl Cat Paws: Toes, Anatomy, and Care](/knowledge/veterinary-medicine/pet-care/polydactyl-cat-paws-toes)
- [Polydactyl Cat Personality: Myth vs Reality](/knowledge/veterinary-medicine/behavior/polydactyl-cat-personality)
- [Polydactyly in Dogs: Extra Toes, Causes, and Treatment](/knowledge/veterinary-medicine/preventive-and-routine-care/polydactyly-in-dogs-treatment)
- [Incomplete Dominance Gene](/blog/guides/incomplete-dominance-gene)

## References

1. [Congenital and Inherited Anomalies of the Musculoskeletal System in Dogs and Cats - Musculoskeletal System](https://www.merckvetmanual.com/musculoskeletal-system/congenital-and-inherited-anomalies-of-the-musculoskeletal-system/congenital-and-inherited-anomalies-of-the-musculoskeletal-system-in-dogs-and-cats). Merck Veterinary Manual.
2. [Genetic heterogeneity of polydactyly in Maine Coon cats](https://pubmed.ncbi.nlm.nih.gov/32067556/). Journal of feline medicine and surgery, 2020.
3. [Clinical characterisation of polydactyly in Maine Coon cats](https://pubmed.ncbi.nlm.nih.gov/26862149/). Journal of feline medicine and surgery, 2017.
4. [The chicken polydactyly (Po) locus causes allelic imbalance and ectopic expression of Shh during limb development](https://pubmed.ncbi.nlm.nih.gov/21465618/). Developmental dynamics : an official publication of the American Association of Anatomists, 2011.
5. [Mutation analysis of a large Chinese pedigree with congenital preaxial polydactyly](https://pubmed.ncbi.nlm.nih.gov/19066618/). European journal of human genetics : EJHG, 2009.
6. [Genetic Instability of a Polydactyl Hypopigmented Cat With Squamous Cell Carcinoma-A Case Report](https://pubmed.ncbi.nlm.nih.gov/32528983/). Frontiers in veterinary science, 2020.

## Further Reading

- [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners)
- [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)
- [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)