What is spinal muscular atrophy (SMA) in Maine Coons?
SMA is a recessive genetic condition identified in the Maine Coon breed that affects the motor neurons controlling muscles in the lower body, typically leading to hind-leg muscle weakness starting at a few months of age.
It's generally not considered painful and is not thought to shorten lifespan, but it does affect mobility. Affected kittens typically appear normal at birth, with a gradual, progressive weakness in the hind legs becoming noticeable around three to four months of age — this can show up as an unsteady or "bunny-hopping" gait, difficulty jumping to heights the cat previously managed easily, or muscle wasting in the hindquarters visible over time. Front-end mobility, appetite, litter habits, and mental alertness are generally not affected by SMA itself, and many affected cats adapt well to indoor life with some accommodations, such as easier access to litter boxes and resting spots without requiring high jumps.
Because SMA is recessive, a kitten only becomes affected if it inherits a copy of the mutated gene from both parents. A cat with just one copy is a carrier — clinically normal and unaffected itself, but able to pass the gene on. A DNA test can sort breeding cats into three categories: clear (no copies), carrier (one copy), or affected (two copies), which lets breeders make informed pairing decisions. Pairing a clear cat with a carrier, for instance, can still produce carrier kittens but no affected kittens, while carrier-to-carrier pairings are the ones responsible breeders specifically avoid.
Because presentation and progression can vary between individual cats, any concerns about a cat's gait, mobility, or muscle development are best evaluated directly by a veterinarian rather than diagnosed at home. If you have questions about SMA testing status for a specific kitten's parents, contact us — we're glad to discuss it, and you can view available kittens as well.