What is NSM?

Maine Coon cats, like cats of many other breeds, have a number of genetic diseases.

The most fatal is NSM - hypertrophic cardiomyopathy of the heart. This pathology is inherited autosomally dominant and has variable penetrance.

And now with the translation, as they say ;)

Coons, as a breed of cats, have a number of features, many of which are simply wonderful: character, size, appearance. BUT there are also unpleasant breed diseases.

Hypertrophic cardiomyopathy of the heart is a genetic mutation, "broken genes" cause the body to malfunction, namely, they reduce the production of myomysin, a protein that is responsible for the normal functioning of the heart muscle (myocardium). The muscle cannot work properly, it loses tone, mobility and becomes less elastic, gradually thickening, which leads to a decrease in the volume of the left atrium.

The first signs of the disease may be shortness of breath, increased fatigue of the Maine Coon. In the future, the development of the disease leads to serious violations of blood circulation and death of the animal.

Unfortunately, a whole complex of genes leads to the development of this disease.

At the moment, genetic tests are being carried out and practiced by many nurseries for all producing animals. They are tested for 2 genes that are most common in the Maine Coon population and are most directly related to the development of the disease. Again, it is worth noting that mutations are just a genetic tendency to develop a particular disease.

Transcript of animal tests:

NSM /NSM is a homozygous pathological mutation, the probability of developing the disease is very high, this status shows an increased genetic predisposition to the development of the disease. Offspring from such an animal will have NSM - heredity, even when mating with a healthy animal according to tests.

NCM/N is a heterozygous mutation, a carrier of a pathological mutation, there is a risk of the disease, since the pathology is inherited autosomally dominant, and therefore, under unfavorable circumstances, there is a risk of developing cardiomyopathy. In breeding such animals, they are used extremely carefully, mating is possible only with animals that are negative according to tests.

N/N - absence of pathological mutations. This status indicates that the animal does not have mutations in the tested pair of genes, the risk of developing the disease is minimal. These are the most suitable animals for breeding work.

It is permissible to use heterozygous animals in breeding programs of nurseries if the animals have a special breeding value for the breeder, but an animal with no pathological mutations should be selected as a partner.

Binding of NCM/N and N/N according to animal tests will never give homozygotes with a pathological mutation. As a rule, when receiving a descendant in the right type from a heterozygous parent without pathological mutations, the carrier is removed from breeding.

The mating of animals with unknown statuses for this disease is by no means unacceptable. This is blind mating: if you're lucky, you won't be lucky!

Mating of two animals with NCM/N tests is also unacceptable, since 50% of kittens from such mating will be carriers of a pathological mutation, 25% will be born with the status of NCM/NCM and another 25% with the status of N/N. Do not rely on luck and believe in the miracle laws of genetics, as the laws of meanness. It is very likely to get all the kittens in the litter of NSM / NSM!

An even greater risk is the mating of NSM/NSM and NSM/N - definitely with such partner statuses there will not be a single kitten without a pathological mutation, 50% of kittens will be born with NSM/NSM.

I would also like to note that the test is not a verdict, but also not an insurance, the test is a tool.

Cardiomyopathy can also affect an animal that is clean according to tests, however, given the increased genetic predisposition to this disease in animals with the status of NSM / NSM and partly NSM / N, annual ultrasound of the heart and cardiologist consultations are recommended.

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. With HCMP, the walls of the heart thicken and the volume of the left ventricle decreases due to this, from where blood enters the general bloodstream when the heart contracts.

Hypertrophic cardiomyopathy can be primary and secondary. Primary HCMP is an inherited disease.  The heritability of this disease has been proven in Maine Coons. Now it is possible to test cats for the presence of this gene by conducting blood tests. In addition to Maine coons, ragdolls, sphinxes, British and American shorthair and their varieties, Norwegian forest cats are predisposed to the development of GKMP. Among other breeds, pathology is less common and the transmission of these genes by inheritance has not been proven. Clinical signs of primary HCMP most often develop at a young age, up to three years.

Secondary HCMP is when changes in the myocardium (heart muscle) develop under the influence of other diseases (for example, hyperthyroidism). In such animals, signs of heart failure can develop either at a significantly older age, or they do not have time to develop at all.

A distinctive feature of this disease is the significant complexity of early diagnosis. In a cat with HCMP, the presence of the disease may first manifest itself as pulmonary edema or death. That is, the signs will not develop for a long time and gradually, they will not be noticed by the owner, but severe (extreme) manifestations of the disease will develop immediately and sharply. Why is this happening? Due to the fact that a cat living in an apartment with a heart condition will not show the owners signs of load intolerance and cats do not cough due to heart disease - this is what dog owners primarily pay attention to and what serves as a reason for a visit to the doctor. They can easily note that the dog used to run 10 km behind the bike, and now when walking often sits down and can't catch his breath. The cat in this situation ceases to put itself under stress - it just sleeps more, moves less, and the owners do not attach importance to this, believing that they just have a lazy cat. And it is almost impossible for a doctor at the reception after interviewing the owners to distinguish a phlegmatic cat with a calm character from a cat that does not move because it cannot. Often we encounter in such cases that signs of heart failure (mainly shortness of breath - frequent breathing and /or breathing with an open mouth) a cat or cat begins to show after stress, which is either the transportation of an animal or a visit to a veterinary clinic for some reason not initially associated with heart disease. Only a small percentage of cat owners with diagnosed GKMP can recall that they noticed that the cat was breathing heavily after the load (provoked by the owner or another animal of the game). At the same time, the insidiousness of this pathology lies in the fact that during examination, auscultation and even on a chest X-ray in the absence of complaints, more than half of the animals with HCMP may not have any deviations.

The mechanism of GKPM development. There is (due to hereditary factors or the action of other causes) hypertrophy (thickening) of the wall of the left ventricle, which reduces its ability to stretch (that is, its "stiffness" increases). In this regard, the pressure in the left ventricle increases, the pressure in the veins of the lungs increases, which with further progression of pathology leads to the development of pulmonary edema or fluid accumulation in the pleural cavity (hydrothorax). The volume of the cavity of the left ventricle decreases due to thickened walls, the volume of blood passing through it decreases and, accordingly, cardiac output.

In the enlarged left atrium, turbulent blood flows (vortices) are created, which contribute to the formation of blood clots in the cavity of the left atrium. Detached blood clots, getting into the central bloodstream, lead to such a serious condition as thromboembolism. Most often, blood clots clog the vessel in the area of femoral artery bifurcation, which is clinically manifested by sudden loss of pelvic limb support and acute pain. Often this complication becomes fatal for a cat, an extremely small percentage of patients recover, more often these are animals with mild symptoms. A recovered animal has a high probability of relapse (repetition of the situation) in the coming months. Of course, the sooner the patient goes to the doctor, the more chances there are to restore blood flow.

Due to the fact that symptoms can develop dramatically and unpredictably, the importance of early diagnosis of HCMP becomes clear.  Examination of young animals without complaints of risk group breeds is necessary for further breeding of healthy animals, patients should be excluded from breeding. Foreign clubs allow animals to breed after several types of tests, the results of which must be confirmed annually.

When should an echocardiography be performed on a cat that has no complaints about the state of health:

1. if it is a cat of a breed from the risk group,
2. if you notice that the cat does not move much or breathes with an open mouth after exertion,
3. if one of the first two signs is combined with the fact that your pet needs general anesthesia.
 
As we wrote above: the disease may not manifest itself, the doctor at the reception during the examination before anesthesia does not detect changes, while in a cat with HCMP, general anesthesia can lead to serious complications in the form of pulmonary edema and death in the coming hours or days after surgery. This applies primarily to young animals who have applied to the clinic for castration. As a rule, these are patients aged about a year, and the vast majority of those who were diagnosed with HCMP had no signs of the disease. The reason for the echocardiography in this case was either the doctor's alertness about the presence of HCMP, or the owners' increased anxiety about the upcoming anesthesia. The detection of HCMP in these animals is not an absolute contraindication to general anesthesia, but it is a higher degree of anesthetic risk, it is a different approach to general anesthesia, it is the need for longer and careful postoperative observation, the possibility of owners in the coming days after surgery in case of complications to urgently contact the clinic.

A source: https://www.oldbluzcoon.com