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Genetics: Maine Coon Cat Hypertrophic Cardiomyopathy (HCM)

Maine Coon cat hypertrophic cardiomyopathy (HCM) usually does not show up until they are an adult although the genetic mutation is present at birth. 

Maine Coon Cat Hypertrophic Cardiomyopathy (HCM) Testing Price: $35.00 per cat, $25 per kitten for two or more kittens from the same litter

Maine coon resting at home

Most Maine Coons develop the disease after 3 years of age but some do not develop it until much later (6- 8 years of age). The Maine Coon DNA mutation is a single base pair change in the DNA.

Several studies indicate that the genetic mutation is fairly common in Maine Coon cats and about 30% of Maine Coons carry the mutation. The disease is referred to as having “incomplete penetrance”. This means that even if a cat has the genetic mutation, the mutation may not actually “penetrate” or lead to the development of full disease in that cat.

DNA test results will indicate if the cat has the mutation on 1 copy of its 2 gene copies (heterozygous) or both gene copies (homozygous). Most cats that are heterozygous for the mutation will NOT get sick. However, most cats that are homozygous (have 2 copies of the gene) will eventually develop the disease and may become sick.

Once you run the DNA test we will send you results that state your cat’s results are either:

Negative – This means that your cat does not have the genetic mutation for Maine Coon HCM. However, this does not mean that your cat can never get HCM since there may be other causes of the disease; it means that it will not get HCM from the MC DNA mutation.

Positive Heterozygous – This means that your cat has 1 copy of the genetic mutation and 1 copy of a normal gene. In the Maine Coon the majority of these cats never get sick. We do not recommend any medications or additional monitoring for your pet, however, if your veterinarian does ever detect any signs of heart disease (murmur, etc) an evaluation with a cardiologist is recommended.

Breeding recommendations

Since it is estimated that about 30% of the Maine Coon population has the mutation we do not recommend withholding all positive heterozygous cats out of the breeding program. Since most cats that are positive heterozygous do not get sick from the disease it may be reasonable to consider breeding these cats to a Negative cat, screening the kittens and trying to select a Negative kitten to keep as a replacement breeding animal in the next litter or so. We would never recommend breeding a positive heterozygous cat to a positive heterozygous cat since this could produce homozygous cats, which are more likely to become sick from this disease.

  • Positive Homozygous– This means that your cat has 2 copies of the genetic mutation. It has the highest risk of developing the disease and has 100% chance of passing the mutation on to all of its kittens. We would not recommend using these cats for breeding purposes.