Hypertrophic cardiomyopathy (HCM) is caused by mutations in sarcomeric proteins, the commonest being MYBPC3 encoding myosin-binding protein C. It is characterised by left ventricular hypertrophy but there is an important pre-hypertrophic phenotype with features including crypts, abnormal mitral leaflets and trabeculae. Here, MYBPC3 is linked to left ventricular hypertrophy.