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Hypertrophic Cardiomyopathy (MYBPC3 gene, Maine Coon)

Hypertrophic Cardiomyopathy (MYBPC3 gene, Maine Coon)

Hypertrophic cardiomyopathy is a disorder characterized by thickening of the myocardium, specifically by increased volume of cardiac muscle tissue in the left ventricle and ventricular septum. It is the most common cardiac disease in domestic cats.

Symptoms

The manifestation of symptoms of hypertrophic cardiomyopathy usually occurs between two and three years of age, although the age of diagnosis may be later. Most affected cats do not experience symptoms immediately. The main clinical signs include congestive heart failure, arterial thromboembolism and a minority even experience sudden death. Congestive heart failure may involve shortness of breath, lethargy and exercise intolerance, and thromboembolism may involve the hind limbs causing pain and bilateral ischemia.

Disease Management

There is no preventive or curative treatment for this disease. Treatment focuses on controlling the symptoms by means of drugs such as antithrombotics to reduce the risk of clot formation.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the cat, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected cat must be carriers of at least one copy of the mutation. Animals that only have one copy of the mutation are not at increased risk of developing the disease, but they can transmit the mutation to future generations. Breeding between cats that carry genetic variants that can cause a disease, even if they do not show symptoms, is not recommended.

Technical report

Hypertrophic cardiomyopathy is a disorder characterized by thickening of the myocardium. Among the genes that have been extensively investigated in relation to this disease is the gene that encodes cardiac myosin-binding protein C (MYBPC3), a protein with sarcomeric function, meaning it is involved in the process of muscle contraction. Although the precise role of the protein produced by MYBPC3 is not fully understood, it is believed that it could interact with myosin or actin, or establish interactions with other sarcomeric proteins. The first variant described (c.91G>C) in this gene was identified in the Maine Coon breed, where a base pair change was identified in a conserved region that affected the protein's conformation. This alteration leads to sarcomeric disorganization. Although initially classified as a dominant autosomal inheritance disease, statistical reports do not seem to find an elevated risk for heterozygous cats (one copy). It is true that this variant has been identified in other feline breeds; however, the guidelines established by the American College of Veterinary Internal Medicine do not recommend genetic testing for MYBPC3 c.91G>C in cats that do not belong to the Maine Coon breed.

Most affected breeds

Maine Coon
Munchkin
Scottish Fold

Bibliography

Akiyama N, Suzuki R, Saito T, et al. Presence of known feline ALMS1 and MYBPC3 variants in a diverse cohort of cats with hypertrophic cardiomyopathy in Japan. PLoS One. 2023 Apr 18