Restrictive cardiomyopathy (RCM)

RCM is a rare type of cardiomyopathy that is characterized by stiffening of the heart muscle, which impairs its ability to fill with blood. In restrictive cardiomyopathy (RCM), the muscle cells in the heart become replaced with abnormal tissue (such as scar tissue). This causes the muscle walls of the ventricles (the lower chambers of the heart) to become stiff, which restricts the movement of the heart. The pumping action of the heart is not usually affected, and the heart can contract to pump blood around the body. However, it is the filling function of the heart, where the heart muscle relaxes and the ventricles fill with blood, that is affected.

This poor filling function means that the ventricles receive less blood than normal, and so blood flow around the body and the heart is reduced. Also, blood gets 'backed up' as it cannot enter the heart as normal, which causes a build-up of pressure. This can cause the atria (top chambers of the heart) to enlarge.

Genetics in Restrictive Cardiomyopathy

RCM can be caused by variants in genes that encode for proteins that are involved in the structure and function of the heart muscle. RCM can be inherited in an autosomal dominant or autosomal recessive manner, depending on the specific gene involved. In some cases, RCM can also be caused by new (de novo) gene changes, which occur spontaneously and are not inherited from either parent.

Mutations in the TNNI3 gene are the most common cause of familial RCM. TNNI3 encodes for troponin I, which is involved in regulating the contraction of heart muscle cells. Other genes that have been linked to RCM include MYH7, MYBPC3, and TNNC1. 

Genetic testing is not always necessary for diagnosing RCM. The condition can also be diagnosed based on clinical symptoms, such as an enlarged liver or reduced heart function.

While RCM is a genetic disorder, it is important to note that not all cases of RCM are caused by genetic changes. Some cases may be due to other factors, such as amyloidosis or sarcoidosis.

For further information (including symptoms and treatment) on restrictive cardiomyopathy, click on the following link to the CardiomyopathyUK website - Cardiomyopathy UK- Restrictive Cardiomyopathy

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