Feline Endomyocardial Restrictive Cardiomyopathy Occurring in One Sibling Pair

Two sibling cats from a single litter died of aortic thromboembolism and congestive heart failure, respectively, at different times. Both of them were diagnosed pathologically as having the endomyocardial form of restrictive cardiomyopathy (RCM), suggesting a possible familial basis for feline endomyocardial RCM. There were significant differences in the pathologic features of the heart between the two sibling cats, and therefore it is likely that multiple genetic factors determining the pathologic phenotype may be involved in the development of this disease. This appears to be the first case report of the endocardial form of RCM occurring in sibling cats.