A novel missense mutation in the myosin binding protein-C gene is responsible for hypertrophic cardiomyopathy with left ventricular dysfunction and dilation in elderly patients.

We studied the clinical features of hypertrophic cardiomyopathy (HCM) caused by a novel mutation in the myosin binding protein-C (MyBP-C) gene in patients and family members of Japanese descent. Previous reports have demonstrated that the clinical features of HCM associated with mutations in the MyBP-C gene include late onset and a favorable clinical course. Recently, some mutations in genes encoding sarcomeric proteins have been reported to be a cause of dilated cardiomyopathy (DCM), as well as HCM. However, mutations of the MyBP-C gene have not been reported as a cause of DCM up to now. We analyzed MyBP-C gene mutations in 250 unrelated probands with HCM and in 90 with DCM. We used electrocardiography (ECG) and echocardiography to determine clinical phenotypes. We identified 17 individuals in 8 families (7 HCM, 1 DCM) with an Arg820Gln mutation in the MyBP-C gene. Overall, 2 (40%) of 5 carriers age >70 years displayed "burnt-out" phase HCM, and one of them had been diagnosed as having DCM before genetic identification. The disease penetrance in subjects age >50 years was 70% by echocardiography and 100% by ECG, and that in those age <50 years was 40% and 50%, respectively. Elderly patients with Arg820Gln mutation may show "burnt-out" phase HCM, and patients with this mutation may be included among those diagnosed as having DCM. Screening of patients with DCM, as well as HCM, for this mutation is of significant importance because patients with this mutation may be diagnosed clinically as having DCM.