If a cat has hyperthyroidism and is experiencing weight loss, increased thirst, and perhaps an unkempt coat, it’s probably something about the environment that caused it. She didn’t inherit the potential to develop the disease from the genes passed down by her parents. But there are a number of feline diseases that do result from what Tufts veterinary geneticist Jerold Bell, DVM, calls “disease-liability genes.” These genes and the illnesses they cause because of their DNA mutations are sometimes more prevalent in cats of particular breeds. But most cats breed randomly, and genetically based diseases are seen throughout the feline population. Dr. Bell has identified the top five, from most to least common.
1. Feline Lower Urinary Tract Disease, or FLUTD. FLUTD is the most common DNA-linked illness to befall cats brought to veterinarians. The incidence rate may be as high as one in 50 cats seen. Persians appear to be at increased risk, Dr. Bell says, while Siamese cats may be at a lower risk than cats of other breeds or mixed breeds. It should be noted that stress — an environmental factor — contributes to the development of FLUTD in cats, but in one experiment, only cats genetically predisposed to the disease developed clinical signs of it when exposed to stressors.
Signs. Straining to urinate, pain during urination, and sometimes blood in the urine.
Treatment. Treatment varies depending on the cause and ranges from anti-inflammatory drugs to surgery for dislodging an obstruction. To prevent recurrence, drugs may be continued after the initial problem has resolved. Dietary changes may also be prescribed along with measures to decrease environmental stress.
2. Diabetes. Diabetes is most commonly seen in cats that are bred randomly. But Dr. Bell says there is also a higher incidence in Burmese cats and possibly Siamese, Norwegian forest, Russian blue, and Abyssinian cats. Obesity is an environmental factor that triggers the genetic potential for diabetes to form. Interestingly, the gene that predisposes us to diabetes is very similar to the one found in cats.
Signs. Excessive thirst, increased urination, increased appetite, and unexpected weight loss.
Treatment. Twice-daily insulin injections, dietary changes and, when necessary, loss of excess weight are the mainstays of controlling feline diabetes. In some cases, the dietary changes (fewer carbohydrates, perhaps more fiber and fewer calories) can lead to a cat being able to stop taking insulin.
3. Lymphocytic (or Plasmacytic) Inflammatory Disease. This disease can strike a cat in one of two ways, either as gum disease (gingivostomatitis) or inflammatory bowel disease, commonly referred to as IBD. Breeds predisposed to these two conditions include Siamese and other Asian cats. The exact genetic mutations that lead to the illnesses in these breeds (and mixed breeds) have not been identified, but genes for IBD have been identified in German shepherds and people. Liability genes for the human version of feline gingivostomatitis have been found as well.
Signs of gingivostomatitis. Hunger with weight loss due to mouth pain. The pain is often made obvious when a cat paws at the mouth. A cat with the condition may also produce excessive and perhaps bloody saliva, in addition to having open sores on her gums (ulcerations) or gums that are swollen and/or bleeding.
Signs of IBD. Abdominal pain, weight loss, fatigue, and symptoms of gastrointestinal upset in the form of diarrhea, vomiting, and rumbling sounds from the abdomen.
Treatment. Control of both conditions in cats often includes dietary changes, anti-inflammatory and immunity-regulating drugs, and minimization of environmental stress. Cats with severe gingivostomatitis may also undergo one or more tooth extractions.
4. Hypertrophic cardiomyopathy. When Dr. Bell first compiled his list, this disease was number 5, not number 4. But more echocardiograms are now performed on cats, improving diagnosis.
By far the most common heart condition affecting cats, hypertrophic cardiomyopathy is characterized by a structural abnormality in the muscle enclosing the heart’s lower chambers, called ventricles. It results in a faulty blood flow, which eventually leads to congestive heart failure.
A genetic mutation that leads to the condition occurs in 33 percent of Maine coon cats. A different mutation in the same gene occurs in 20 percent of Ragdolls. And in 2021 a liability gene for hypertrophic cardiomyopathy was discovered in the Sphynx breed. Many other cats are affected as well, including Norwegian forest cats, Persians, Chartreux, Bengals, and Birmans, although the faulty genes have not been identified for those breeds. Mixed breeds may also develop hypertrophic cardiomyopathy.
Signs. Lethargy, loss of appetite, difficulty breathing, shortness of breath.
Treatment. Treatment depends on the severity of the disease. Hypertrophic cardiomyopathy cannot be cured. But medications can help keep symptoms from progressing as rapidly as they would otherwise, in some cases keeping a cat alive and happy for years.
5. Polycystic Kidney Disease. This condition used to be number 4 on Dr. Bell’s list. The increased availability of genetic testing in cats has decreased its rate of occurrence because of improve breeding.
It takes only one defective gene to cause polycystic kidney disease in a cat, which can lead to kidney failure and premature death long before she reaches age 10. A cat needs the faulty gene from only one parent to develop the illness. If she inherits it from both, she will die in utero.
The problem gene is present in 38 percent of Persian cats as well as in high frequencies in Himalayan and other Persian-derived breeds. It’s in 6 percent of all cats worldwide. Some cats are lucky enough not to proceed to full-out kidney failure and instead simply develop a few cysts that don’t interfere with kidney function.
Signs. Signs of the illness are similar to the signs of a number of other feline diseases: increased drinking and urination, diminished appetite and subsequent weight loss, nausea, vomiting, and lethargy. A proper workup is necessary to get to the cause.
Treatment. Treatment is the same as treatment for other diseases that lead to kidney failure: dietary manipulation, fluid therapy (sometimes it progresses to intravenous administration of fluids at a home), and medications to make a cat more comfortable.
Dr. Bell points out that only some hereditary diseases have genetic tests. For the others, any cat you’re thinking of breeding should undergo a pre-breeding health examination to ensure that they are not showing clinical signs of those diseases. Commercial genetic testing companies now run genetic testing panels for feline hereditary diseases, as well as genetic markers for oral biome health and other novel genetic testing.
My girl has hyperthyroidism! Right now she keeps her thtroid problem is a cbc and t4 and she uses hills throid cat food. And she uses the hill kibble as her cat food. And it helps !