Hypertrophic Cardiomyopathy (HCM) is a disease that causes thickening of the heart muscle. As the muscle becomes progressively thicker, less blood volume is pumped around the body. This leads to symptoms of heart failure including labored breathing, lethargy, weakness, collapsing episodes, and even sudden death. HCM is the most common form of heart disease in cats.
While the cause of HCM is not known, researchers have discovered that there is a genetic component that predisposes some cats to developing HCM.
DNA Tests For HCM Are Breed Specific
There are currently three HCM genetic mutations that have been identified in three breeds of cats:
- Maine Coons: In 2005, the gene that causes HCM in Maine Coons was identified and shortly after, a DNA test for the gene was available to the delight of breeders. Although scientists had identified one HCM mutation in Maine Coons, they know that this mutation to not responsible for ALL cases of HCM in the breed. Already, there have been cases of Maine Coons that have been diagnosed with HCM that when DNA tested were not positive for the HCM gene. This means that there is most likely more than one mutation in Maine Coons that causes HCM.
- Ragdolls: In 2007, a different gene mutation for HCM was identified in Ragdolls. To date, all Ragdolls confirmed with HCM by ultrasound have also tested positive for the Ragdoll HCM gene mutation, suggesting that there may be only one mutation in Ragdolls that predisposes the cat to develop HCM.
- Sphynx: In 2020, a DNA mutation was identified in about 60% of affected Sphynx Cats. This mutation is also found occasionally in healthy adult Sphynx cats who do not have the disease. This referred to as “incomplete penetrance”. This means that even if a cat has the genetic mutation, the mutation may not actually penetrate or lead to the development in full disease in that cat. Importantly since this mutation only appears to have identified about 60% of affected cats, it appears likely that there is at least one other Sphynx cat HCM Mutation.
HCM
HCM can also result from other diseases so when HCM is diagnosed other causes such as high blood pressure or thyroid problems must be ruled out.
In humans, over 130 mutations spread over 10 genes that lead to HCM have been identified, suggesting there could be more than one HCM gene mutation in any single breed of cat.
The gene which causes HCM is not the same from one breed to another, therefore, none of the DNA tests for detecting HCM in Maine Coons, Ragdolls or Sphynx is applicable to other breeds of cats.
Research To Identify Other HCM Gene Mutations
Research To Identify Other HCM Gene MutationsMutations responsible for HCM in breeds of cats other than the Maine Coons, Ragdolls and Sphynx have not yet been identified (2323). If or when HCM gene mutations are identified in other breeds, they won’t be the same mutations that cause this disease in Maine Coons, Ragdolls or Sphynx.
There is currently ongoing research looking for further mutations that may contribute to HCM in Maine Coons and Ragdolls, along with other breeds in which a higher prevalence of HCM has been reported or suggested. The breeds include Persians, Bengals, Norwegian Forest Cats and Sphynx.
Around 30% of Maine Coons have genetic mutations associated with risk of developing HCM, and Ragdolls are also known to be at higher risk for the disease. Other at-risk breeds include the Persian, Birman, Bengal, Turkish Van, and the Abyssinian. Research has also demonstrated the prevalence of HCM in British Shorthairs (see Granström et al., 2011).
- Maine Coons: A31P & MYBPC3 mutations associated with HCM in Maine Coon cats and their outcrosses.
- Ragdolls: R820W & MYBPC3 mutations associated with HCM in Ragdoll cats and outcrosses as described by Meurs et al. 2007. Autosomal dominant (incomplete penetrance).
- Sphynx: The ALMS1 gene mutation was identified and found in about 60% of affected Sphynx Cats. This mutation is also found occasionally in healthy adult Sphynx cats who do not have the disease. This referred to as “incomplete penetrance”. This means that even if a cat has the genetic mutation, the mutation may not actually penetrate or lead to the development in full disease in that cat.
- Scottish Fold: A variant in the ALMS1 gene has been identified in this breed and is being studied for its link to HCM.
- Munchkin: This breed has also been identified as carrying the ALMS1 variant found in Scottish Folds.
- Minuet: This breed, related to the Munchkin, has also been identified as carrying the ALMS1 variant.
- Devon Rex: Studies are underway to identify genetic markers for HCM in this breed.MYH7
Incomplete Dominance of HCM mutations is a common finding in Maine Coons, Ragdolls, Sphynx and human beings with genetic mutations associated with Hypertrophic cardiomyopathy.
Good News For All Breeds
While the DNA tests applicable to Maine Coons, Ragdolls and Sphynx are for those specific breeds, because they haves similar “house cat” ancestry as the Persian/Exotic, American Shorthair and British SH, it is hoped that further research and testing may reveal the HCM gene for these breeds and produce a viable DNA test for them.
