HCM IN SPHYNX

What is HCM?

Hypertrophic Cardiomyopathy – the most common of acquired heart diseases in all breeds of cat including domestic cats. It is a heart muscle disease where the left ventricle becomes thickened over time. It can happen at any age. It causes the heart to stop functioning as it should which can in turn cause blood clots, and it otherwise affects the structure and functioning of the heart. There is no cure, but the condition can be medicated. Some cats with HCM can live long and happy lives as long as they are medicated. It is a disease also know in humans. Some cats will only have a mild case, whilst others may be severe which may cause death.

Is sphynx the only breed it happens to?

There are many breeds known to be affected by HCM, including domestic cats, Maine Coons, Ragdolls, Norwegian Forest Cat, Siberian, just to name a few.

Why should that mean anything to me?

With sphynx, HCM is thought to be genetic, although it can skip generations and turn up at any time. If an ancestor of a sphynx has been diagnosed for HCM, there is a disposition for the risk, but it does not mean the cat will develop HCM.

How can you test for it?

We recommend that all sphynx are tested both by the new HCM DNA test and by cardiologist scanning. Due to the nature of the disease, you cannot test by cardiologist scan until they are fully grown, usually around 12 months old. We recommend this for all breeding cats and then annually. For all pet sphynx we recommend testing at least every 18 months from 12 months of age. Testing can vary in cost and is expensive, but worthwhile.

In late 2020, Dr Kate Muers of North Carolina State University discovered the gene responsible for 60% of HCM cases in sphynx - indicating that there is more than one gene responsible for HCM in sphynx, with each sphynx carrying two genes which may be of different sequences. The current cost of the test is US$40, and Further information is available here. This one off test is recommended for all sphynx and can have varying results:

Negative – This means that your cat does not have the known genetic mutation for Sphynx HCM and is unlikely to be affected by this mutation. 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 known Sphynx DNA mutation.
Positive Heterozygous – This means that your cat has 1 copy of the genetic mutation and 1 copy of a normal gene.
Positive Homozygous – This means your cat has 2 copies of the known genetic mutation and could be affected by HCM.

Recommendations for Breeders:

At this time, NCSU does not recommend withholding all positive heterozygous cats (1 positive gene) out of the breeding program. Since many cats that are positive heterozygous may 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. NCSU does not recommend breeding a positive heterozygous cat to a positive heterozygous cat since this could produce homozygous cats, which will most certainly pass on the mutation. It is also not recommended that any positive homozygous cats are bred.

Please Note:

There is no value in dna testing sphynx for HCM using HCM tests for other breeds, only the sphynx specific HCM DNA test
Pro-BNP Blood test may indicate an issue with the heart, but it is not HCM specific. There is also a large error factor when using this test to diagnose HCM in sphynx
Echocardiogram – this is the gold standard for testing sphynx for HCM, and should be done by a feline cardiologist, not a general vet. There are currently 7 certified veterinary cardiologists in Australia. When purchasing a sphynx please ask to see original documentation of HCM results and if not possible, then ask for authority to contact the specialist to verify results.

Australian Based Cardiologists:

Dr Fiona Meyers (formerly Campbell) BVSc(Hons), MANZCVS, PhD, Dip ACVIM (Carrara, QLD) www.vss.net.au
Dr Brad Gavaghan BVSc MACVSc FACVSc (Brisbane, QLD) www.vss.net.au
Dr Geoff Nicolson, BVSc, MVS, DECVS (QLD, mobile Australia) www.vcsaustralia.com.au
Dr Richard Woolley, BVetMed DipECVIM-CA(Cardiology) MRCVS, www.cprvictoria.com.au
Dr Rita (Manreet) Singh BSC,BVNS(Hons) Dip Vet Clin Stud, FACVSc, Dip AVCIM (Sydney) www.sashvets.com
Dr Damon B Leeder, BVSc (Hons 1), DACVIM (Cardiology) www.vetcardiacimaging.com/
Dr Niek Beijerink DVM, PhD, Dip ECVIM-CA (Camperdown, NSW) www.uvths.com.au (now based in Netherlands, part time UVTH)
Dr Chris Lam, BA BVSc (Hons 1st Class), Cardiology Resident www.vss.net.au

New Zealand Based Veterinary Cardiology Specialists:

Dr Jacqui Huxley BVSc CertVC DVC MVM MRCVS, Christchurch, Palmerston North, ad-hoc NZ mobile service www.apexcardiology.org
Dr Richard Lucy, BVSc MANZCVS (Radiology) Cert VC DipVCS, various locations throughout NZ - www.thereferralcentre.co.nz
Dr Joon Seo, BVSc MVetMed(dist) DACVIM (Cardiology) MRCVS, Schnapper Rock, www.arcvets.co.nz
Dr Mark Owen, BVSc DipECVDI FANZCVS (Radiology), www.nzradvet.co.nz

What does this mean for my naked?

When you are considering buying a sphynx, please verify the breeders stance on testing and ask for copies of current documentation (Scan and DNA results) and/or guarantees against HCM. Also ask for a copy of the pedigree and use the following websites to investigate the known incidence of HCM in those pedigrees before purchasing (there are more websites available, but not all breeders list results):

http://www.pawpeds.com/db/?p=sph&date=iso

http://www.sphynxrexbreeders.nl/HCM/view/

http://www.sphynxclub.fr/basecmh/

http://www.archcertify.org/

FAQ

The HCM testing ultrasounds only prove at that time that the cat does not have hcm.

This is true, much the same way that when a human tests negative for any virus or disease they could test positive at any time afterwards if predisposed or exposed. However measurement taken by the cardiologist give a good indication of what will happen in the next 12 months, particularly when compared to previous results from the same cat. It is important to have regular scans to indicate ongoing heart health.

Avoid inbreeding as that is a factor in hcm.

Partially true – if ancestors carry hcm it is more likely that offspring will carry it. However in sphynx this is a big unknown at this time as it can skip through generations and no pattern has been identified. With the identification of one of the genes responsible for HCM in sphynx, it is important that breeders progress their lines to no known HCM genes within breeding cats.

Previous breeders of the same lines have scanned and have no positive results, so there is no need to test.

False Breeders who don’t test can easily they have no hcm as if there is no testing there can be no identification. Also many breeders who do test do not advertise that they have had a positive cat.

An hcm scan per cat is $330 or more and is not a true indication whether the cat will develop for hcm.

False – an ultrasound hcm scan annually is currently the gold standard for testing. The test works by measuring tissues and comparing to the standard for HCM diagnosis as well as the cats previous scans, this is the best indicative test that currently exists at this time.

HCM scanning is a waste of money.

False – when cats are tested regularly and the tests (with pedigrees) submitted to research organisations/databases no matter what the result, these worldwide results can be researched together and hopefully a pattern of affection identified. The 2020 identification of one gene responsible for HCM in sphynx is another tool to be used conjointly with scanning. For future owners of breeds that suffer HCM, these tests should be compulsory for current owners and breeders.

Do breeders guarantee their kittens against hcm

Some provide a warranty. Until the exact cause and all genes are known it is impossible for any breeder to predict what will be affected – but what responsible breeders do will be to provide you a warranty against HCM – it does require some actions required by the owner and also provides actions that the breeder will take if a cat is diagnosed as HCM positive.

Some breeders use cats whose ancestors have had hcm

Yes, this is true for all sphynx. Particularly when the sphynx breed was first identified in the 1960’s and HCM testing was not done. It was later found in older cats and this is how it was identified as an issue – particularly when those cats had bred for a number of years. It is possible that all sphynx have HCM cats in their pedigrees – in older generations. It did not help that outcrossing was done with other HCM affected breeds such as Devon Rex and Ragdolls. If a current breeding cat is diagnosed with HCM the responsible breeder will desex the cat immediately, notify all buyers of those lines and have the cat assessed for treatment

Pet owners think that by hcm scanning and/or DNA testing that means that their kittens are safe

False. If the buyer is not already aware, a good breeder advises them on all aspects of HCM

North Carolina State University Notes:

Sphynx cat hypertrophic cardiomyopathy (HCM) usually does not show up until they are an adult although the genetic mutation is present at birth. The age of presentation of disease is variable with many cats developing the disease between 2-3 years of age and some developing it much older (8 -10 years of age).

We identified a DNA mutation 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. This is also a common finding in Maine Coons, Ragdolls and human beings with genetic mutations associated with Hypertrophic cardiomyopathy.

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

DNA test results will indicate if the cat has the mutation on 1 copy of its 2 gene copies (called heterozygous) or both gene copies (homozygous). At this time, we do not know if the risk of developing disease is higher in cats that are homozygous for the mutation than heterozygous.

HCM is not necessarily a death sentence. Many different breeds are affected including domestic cats. Whilst there is no cure, there are different medications available to help to control the disease. There are HCM affected cats who have lived to 15+ years and have passed from other causes.