**4. Restrictive cardiomyopathy**

Familial restrictive cardiomyopathy (RCM) is a rare disease which is inherited in autosomal dominant pattern with incomplete penetrance (Katritsis 1991). The exact prevalence of RCM is unknown (Elliott, 2008). In childhood, RCM accounts for 2–5% of cardiomyopathies and has a grave prognosis (Kaski, 2008.)

RCM is characterized by abnornal diastolic function, which has a restrictive filling pattern, a reduced diastolic volume of one of the ventricles or both ventricles, enlargement of the atria, pulmonary hypertension and heart failure. In the early stages of the disorder the systolic function may be normal, but as the disease progresses, the systolic function generally declines (Kushwaha, 1997).

The familial RCM is linked to the cardiac troponin genes. RCM1 is caused by a mutation in the *TNNI3* gene on chromosome 19q13. This gene encodes the cardiac muscle isoform of troponin 1. RCM2 has been mapped to chromosome 10q23. RCM3 is caused by mutation in the *TNNT2* gene. Mutations in the sarcomere gene, alpha-cardiac actin gene (*ACTC*) have also been reported to cause RCM,

In many cases RCM can be observed overlapping with either HCM or DCM. (Kamisago, 2000; Olson, 2002; Zang, 2005; Kaski, 2008).
