· 2 min read
Maine Coon SMA: the test that worries buyers more than it should
Spinal muscular atrophy sounds alarming and is easy to screen out. What the SMA test detects, what an affected cat's life looks like, and why carriers are fine.
Anna Bronsky
Co-Founder of TrueKitten, a verified Maine Coon marketplace
Short answer: SMA is fully preventable with a cheek swab, and it is not the death sentence the name suggests. Spinal muscular atrophy in Maine Coons is autosomal recessive — a cat needs two copies to be affected — so a single DNA test on the parents removes the risk entirely.
What the test detects
SMA is caused by a known deletion affecting the LIX1 gene. Because it is recessive, three outcomes exist:
- Clear — no copies. Cannot produce affected kittens with any partner.
- Carrier — one copy. Completely healthy, and safe to breed to a clear cat.
- Affected — two copies. Develops the condition.
Two carriers bred together is the only combination that can produce affected kittens. That is why the test is powerful: it takes one swab per parent to make the outcome impossible.
Why a carrier is not a problem
This is where SMA differs sharply from HCM, and where buyers often over-react. An SMA carrier is a healthy cat with normal life expectancy. Excluding every carrier from breeding would shrink an already limited gene pool for no health benefit — carrier-to-clear pairings produce no affected kittens.
If a breeder tells you a parent is an SMA carrier and the other parent is clear, that is a breeder who tested and understands their own results. It is a good sign, not a red flag.
What an affected cat’s life is like
Affected kittens show signs in the first few months — an unsteady, swaying gait and reduced muscle mass in the hindquarters. The condition affects movement rather than causing pain, and affected cats can live comfortably as indoor pets.
That matters for how you read the word “atrophy” on a health sheet. It is not a comparison to the human condition of the same name.
What to ask for
Ask for the SMA status of both parents, on a lab document naming each cat. Clear-to-clear and clear-to-carrier are both fine; carrier-to-carrier is the pairing to ask about.
And keep SMA in proportion: it is a solved problem with a swab, unlike HCM, where the DNA test alone is not enough. If you want the full list, these are the questions worth asking.
Keep reading
Yes. UC Davis puts HCM incidence at 5.4% in Maine Coons without the A31P mutation and 5.4% in cats with it — the DNA test cannot see the heart.
An echocardiogram is a snapshot, not a certificate. Why breeding cats are rescreened on a schedule, and how to tell whether a result is still meaningful.
Negative, carrier and affected are three different things, and two of them get confused constantly. How to read an A31P result without over- or under-reacting.
