Biallelic PTVs in MYBPC3, TNNI3, MYL2 and MYL3 are associated with severe, early-onset CM phenotypes, which can include additional features such as atrial and ventricular septal defects and skeletal myopathy (Fig. 4a,b, Extended Data Fig. 3a and Supplementary Table 5). The gene discussed is MYBPC3; the disease is cutaneous mastocytosis.