Feline Hypertrophic Cardiomyopathy in the Sphynx Cat
and Other Problems Concerning Diagnoses
by Judy Webb Gunby
One of the biggest myths about the Sphynx is that they are a breeze to take care of. A simple rub down with a baby wipe and they are ready to go. Due to a lack of hair, many think this should make them much easier to get ready for the show. Ask any Sphynx exhibitor and they will tell you this is simply not true.
Judges want to see clean Sphynx on their tables. This includes nails, ears, eyes, mouth, hind-ends and clean, clear skin.
This issue‘s grooming topic is going to focus mainly on some ideas for that perfect ―show bath to ensure your cat looks its best on show day. It‘s good to start thinking about the grooming steps you want to have in place at least one week prior to the show.
I like to do a thorough ear and nail cleaning sev-eral days prior with daily checks to remove any newly accumulated dirt and oil. This prevents last minute stress to the cat and also irritation to their ears (which can cause the cat to hold them funny). A mild ear cleaner, baby wipes & q-tips (being careful not to go too deep) will work well in cleaning the ears. Make-up & Facial cleaning cloths are great on getting grease off the nails. For those tough spots, a little nail scraping might be needed.
Feline hypertrophic cardiomyopathy (HCM) is a disease of the left ventricular myocardium. It may cause congestive heart failure, sudden death, or arterial thromboembolism in affected cats. Accurate diagnosis of HCM necessitates a com-bination of tools be utilized, such as thoracic radiography, and echocardiography.
Feline HCM has been found to be Autosomal Dominant.
While a specific marker has not yet been found in the DNA of the Sphynx cat, investigators have found a pattern in families of cats indicating an autosomal dominant mode of inheritance. Information published by the American Accredita-tion HealthCare Commission, and reviewed on 7/25/03 by Douglas R. Stewart, M.D., Division of Medical Genetics, Hospital of the University of Pennsylvania, Philadelphia, PA, for an autosomal dominant disorder: If one parent has an abnormal gene and the other parent a normal gene, there is a 50% chance each offspring will inherit the abnormal gene, and therefore the dominant trait. In other words, if it is assumed that 4 offspring produced from a couple in which one parent has an abnormal gene for a dominant disease, the statistical expectation is for: 2 offspring with no disease; 2 offspring with the disease. This does not mean that any offspring will necessarily be affected. What it does mean, however, is that each offspring in this case has a 50:50 chance of inheriting the disorder. It also means that offspring who do not inherit the abnormal gene will not develop or pass on the disease.
Breeders, therefore, can assume that an affected cat would produce kittens, each having a 50:50 chance of having the disease. If there was a fool-proof way to test cats, we would, of course, eliminate those affected from our breeding program. The autosomal dominant trait of this disease clearly explains how HCM can appear to simply ―disappear from a cattery line.
Evidence of HCM
In May of 2004, in an article entitled Feline Hypertrophic Cardiomyopathy: Advice for Breeders, by Mark Kittleson, DVM, PhD, DACVIM (Cardiology), School of Veterinary Medicine, University of California, Davis, Rebecca Gompf, DVM, MS, DAC-VIM (Cardiology), College of Veterinary Medicine, University of Tennessee, and Susan Little, DVM, DABVP (Feline), Vice-President, Winn Feline Foundation was published concerning HCM in felines. In this paper, reference is made to the fact that HCM has been proven to be an autosomal dominant trait in the Maine Coon and the American Shorthair. Sphynx breeders have been known to out-cross with the American Shorthair. In the American Shorthair, the disease is, in many cases, not detectible until later in life. However, one must consider in any breeding program that outcrossing to the American Shorthair could, and in fact will, convolute the genetic study with yet other genetic possibilities which are known to be breed specific.
Dr. Meurs, of Washington State University, has found genetic differences in felines expressing HCM which are similar to that in people (the beta-myosin heavy chain). However, those differences found in the beta-myosin heavy chain were not the same differ-ences which affected the production of the protein. Dr. Meurs was looking at other genes that make up the proteins which are part of the ―contractile element of the heart – the left ventricle – to see if they are responsible for familial HCM, which includes the myosin light chains and myosin binding protein C genes. As of 2007, Dr. Meurs turned her attention to the myosin binding protein C genes. According to the 2007 report to The Winn Feline Foundation, ―Her findings indicate that in affected cats, a mutation within the myosin heavy chain gene occurs, but that the mutations are at different locations within this specific gene for each breed. This finding is an important step in finding a genetic code for the expression of HCM in the Sphynx, and the other breeds in this study.
DNA research in genetics is new; in fact, so new that investigators learn new things every day as they test the DNA in blood samples drawn from affected felines, and information they receive from cardiologists around the world, which they input into their database. It is, and has been, through the cooperation of the catteries that have submitted their information, that great strides in learning more about this disease in our breed are underway.
How to Test for HCM
HCM is most accurately diagnosed using ultrasound of the heart, but it may not always detect the disease in cats where changes in the heart are minimal and have not yet led to degeneration. Other diseases that mimic HCM can be ruled out by blood pressure measurement and blood testing for hyperthyroidism. But the best test for HCM is an echocardiogram performed by a board-certified radiologist or cardiologist.
How Often Should My Cat Have an Echocardiogram?
It is recommended that breeding cats have an echocardiogram yearly during their breeding years. Examining retired cats periodically is also advantageous as this may allow the identification of affected cats that have offspring in a breeding program.
Can My Kittens Have HCM even when both parents test negative?
Usually one of the parents have the disease but was misdiag-nosed, although spontaneous mutations have occurred, accord-ing to Drs. Kittleson, Gompf, and Little. Therefore, there is no possibility of ever declaring a cattery ―HCM free due to the nebulous nature of this terminology.
Summary and Research Update
There is a lot of work yet to be done to find a genetic marker for HCM in the Sphynx breed. Research is costly, and this cost necessitated coordinating with other breeds similarly affected. Therefore, the Norwegian Forest Cat, the Ragdoll, and the Sphynx are all part of the same ―triage of study. This will eliminate costly redundancy in testing. Investigators do know that, in many cases, there is earlier onset of this disease in the Sphynx than in other breeds. The reason for this is currently unknown.
In 2007, Kathryn M. Meurs, DVM, PhD, DACVIM of Wash-ington State University released her findings in a report to The Winn Feline Foundation concerning her evaluation of the gene thought to play a part in identification of HCM in the triage of cats under study, the Ragdoll, Norwegian Forest Cat, and Sphynx. Her findings indicate that in affected cats, a mutation within the myosin heavy chain gene occurs, but that the muta-tions are at different locations within this specific gene for each breed. This finding is an important step in the discovery of a genetic code for the expression of HCM in the Sphynx, and the other breeds in this study.
In 2008, Dr. Meurs hypothesized that a mutation of the alpha tropomyosin gene could be associated with the expression of HCM. She is now studying both affected and unaffected Sphynx to do a comparative study of these genes. If anyone has a Sphynx that is HCM negative, and is at least 6 years of age or more, Dr. Meurs would like to have a blood sample. Please let me know if you would like to participate in this study, and I will send you the information. You may contact me at firstname.lastname@example.org.
The HCM study continually needs money, as every year approval is sought for re-admission to the study. Winn, working through the University, matches money every year given by the many breeders that continue to help with this project. They need participating catteries for pedigrees, ultrasounds, and blood samples, and people who are willing to help fund this on-going project.
If you are willing to help, please go to this website, mark the amount you wish to donate, and then mark your donation for Sphynx HCM research. Your donations are tax deductible.
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