Causes of restrictive cardiomyopathy are -

Restrictive cardiomyopathy is characterised by a primary decrease in ventricular compliance , resulting in impaired ventricular filling during diastole. Restrictive cardiomyopathy can be idiopathic or associated with systemic disease that also happen to affect the myocardium for example radiation fibrosis, amyloidosis, sarcoidosis, or products of inborn errors of metabolism Robbins 9 th edition page no. 401