Genetics and Health: Part 3 — Entropion & Hip Dysplasia

Today we’re going to talk about two conditions that often cause confusion among cat owners and even veterinarians: entropion (eyelid rolling inward) and hip dysplasia.

And the very first thing every cat owner must know:There are NO genetic tests for these conditions.Because neither entropion nor hip dysplasia are genetic diseases.They do not come from DNA mutations.They cannot be detected by a lab.They are not part of any official genetic screening panel.

Yet many vets — and many owners — keep repeating that these issues are “hereditary.”

And here is what usually happens:• a cat develops a problem• the veterinarian says: “This is hereditary.”• the owner runs to the breeder: “You sold me a sick kitten.”• the breeder is confused and helpless, because all DNA panels are clear

Some breeders even end up paying other people’s vet bills.

So let’s break this down scientifically and calmly.

Veterinary specialists note that Maine Coons are more prone to entropion and hip problems than many other breeds.

There is a simple explanation for this:Maine Coons are a large, slow-developing breed.Their growth continues for up to 3.5 years, while most other breeds finish developing by around 9 months.

This makes them more likely to show mild entropion while the face is still maturing, because the entire skull and skeletal structure continue to develop for years — and the same prolonged growth period also explains why Maine Coons can temporarily show mild joint or hip instability during adolescence.

But here is the important part:There is no proven inheritance pattern and no identified mutation for either entropion or hip/joint issues in cats.

Entropion

Entropion is a mechanical or anatomical issue of the eyelid.The eyelid rolls inward, causing the eyelashes to rub against the cornea.

Hip dysplasia follows the very same principle — it is also a mechanical or structural problem, not a genetic one.Hip dysplasia simply means that the hip joint is not sitting perfectly in place or has been affected by trauma, inflammation, or uneven development during growth.It is a physical alignment issue, not a DNA mutation.

In both conditions — entropion and hip dysplasia — the underlying mechanism is the same.

There are three general causes:

1. Congenital (from birth) — very rareEven in these cases, the cause is anatomical, not genetic.A kitten may temporarily have unusual proportions: rounder cheeks, larger eyes, weaker eyelid muscle tone.This can slightly change the eyelid angle.As the kitten grows and the face stretches out, the condition typically resolves on its own.

Entropion can only develop from acquired causes.This happens because of: trauma, inflammation, allergies, infection, irritation, swelling.When the eye becomes irritated, the tissues react.The eyelid position changes as a response to irritation, not genetics.

Sometimes a tiny irritant — dust, debris, a scratch, infection, or allergy — triggers a protective spasm of the surrounding muscles.The muscle tightens, pulls the eyelid inward, the eyelashes begin to rub against the cornea.

This is a mechanical, tissue-level reaction, not a hereditary disease.

Hip issues in cats can be:

• congenital (present at birth, but not genetic)• acquired (developing later due to injury or physical stress)

And this is where a huge confusion happens:Many owners — and even some veterinarians — treat congenital and genetic as the same thing.

They are NOT the same.

Congenital hip dysplasia can occur because of:• incorrect fetal position in the womb• maternal trauma during pregnancy• complications during birth• mechanical injury while the kitten is being delivered

These are physical events, not DNA mutations.

And here is the key:If a kitten truly had congenital hip dysplasia, it would be obvious immediately:— the kitten would not be able to stand on its hind legs— it would not walk— the defect becomes visible at 2–3 weeks of age, when kittens begin to stand

A kitten with real congenital dysplasia cannot walk normally from day one.

Crucial Point:If a kitten leaves the breeder’s home walking normally on all four legs, without pain — it does NOT have congenital hip dysplasia.

A healthy kitten cannot suddenly “develop” dysplasia out of nowhere.There must be an external, physical cause.

Acquired hip issues come from trauma — exactly like in humans.This can happen when a cat miscalculates a jump, slips, twists a leg, overstretches or tears ligaments, falls from a height, injures the hip during a sudden movement, or gets into rough play.

Anything that can happen to a human ankle or kneecan happen to a cat’s hip.

And just like people don’t blame their ancestors when they twist an ankle — cats don’t get joint injuries from “genetics.”It is a mechanical injury, not a hereditary defect.

The Marketing Myth

I need to clarify one very curious marketing invention.I don’t know who came up with it, but honestly — it’s brilliant in its own twisted way.

Some veterinary clinics have started replacing real genetic testing with X-ray images.Yes, you heard that right.

They loudly declare that hip problems in cats are “genetic,” and therefore they invented a brand-new “genetic test”: expensive hip X-rays under anesthesia for breeding cats.

And the funniest part?Some breeders actually do it — simply because nobody ever explained the difference to them.

Let me explain clearly.

A genetic test analyzes DNA mutations inside living cells.A DNA panel gives objective results — Clear, Carrier, or At Risk — based on known, mapped, scientifically verified genes.

Hip dysplasia is not one of these genes, because:• no mutation has been identified• no inheritance pattern is confirmed• no DNA marker exists• no laboratory in the world offers such a test

So the phrase “genetic hip dysplasia” in cats is… scientifically meaningless.It might as well be “genetic pink unicorn syndrome.”

But since there is no gene and no DNA test, clinics had to get creative.So a new revenue stream appeared: hip X-rays for breeding cats — under anesthesia, of course, to make it extra dramatic and extra expensive.

What does a hip X-ray show?Only the shape of bones.

What does it NOT show?— DNA— inherited traits— genetic disease

It can reveal trauma, misalignment, inflammation, muscle imbalance, or an old injury — but it will never tell you whether something was inherited.

And yet many vets confidently tell owners:“This is genetic, we need to X-ray the parents.”

Why?Because X-rays under anesthesia pay well.

Breeders — who usually aren’t experts in molecular genetics — get scared and worried about their reputation, and end up X-raying perfectly healthy breeding cats, exposing them to unnecessary radiation and unnecessary anesthesia.

This is not animal welfare.This is not genetics.This is simply a misunderstanding being used as a profit machine.

Supporting Healthy Bone and Eye Development

The most important foundation for strong bones, stable joints, and healthy eyes is a proper lifestyle — not a genetic test, not an X-ray, and not a magic supplement.

A cat needs three things:• balanced nutrition with calcium, phosphorus, high-quality protein, and natural vitamin D;• regular movement to strengthen muscles and stabilize joints;• fresh air and real sunlight to support natural metabolic processes.

Please remember:Vitamin D cannot be produced effectively through a window, and you cannot replace it with supplements alone.The feline body requires natural UVB light to synthesize vitamin D — and proper vitamin D levels are essential for calcium absorption and the development of strong bones, cartilage, and connective tissue.

If safe outdoor time isn’t possible, you can use a UVB light source (such as a reptile UVB lamp) for 1–2 hours per day.This helps stimulate natural vitamin D production and supports healthy skeletal and ocular development.

Strong bones, healthy joints, and clear eyes — these are the results of biology, care, and environment, not “genetics” invented in a clinic.