Sarcomeric versus Non-Sarcomeric HCM

Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiovascular disorder and is characterized by left ventricular hypertrophy (LVH), which is unexplained by abnormal loading conditions. HCM is inherited as an autosomal dominant trait and, in about 40% of patients, the causal mutation is identified in genes encoding sarcomere proteins. According to the results of genetic screening, HCM patients are currently categorized in two main sub-populations: sarcomeric-positive (Sarc+) patients, in whom the causal mutation is identified in a sarcomeric gene; and sarcomeric-negative (Sarc−) patients, in whom a causal mutation has not been identified. In rare cases, Sarc− HCM cases may be caused by pathogenic variants in non-sarcomeric genes. The aim of this review is to describe the differences in the phenotypic expression and clinical outcomes of Sarc+ and Sarc− HCM and to briefly discuss the current knowledge about HCM caused by rare non-sarcomeric mutations.