Hypertrophic cardiomyopathy (HCM) is the most common heart disease in Ragdoll, Main coon and crossbreed cats. One of the possible causes of the disease is the mutation R820W within the MYBPC3 gene encoding the myosin binding C protein which is a component of sarcomeres. This mutation is autosomal dominant and it is a point mutation associated with the conversion of highly conserved arginine to tryptophan. The arginine replacement by tryptophan leads to changes in the myosin structure that are important for the functioning of the entire sarcomere and results in abnormal interactions between the myosin binding protein C –and other proteins. The disease progresses to congestive heart failure. The characteristic symptoms of the disease are short breath, pulmonary edema and exercise intolerance. Symptoms resulting from thromboembolic episodes as well as sudden cardiac death are also frequently observed.