MYOM2 and rheumatic heart disease: The immune response against the M protein component of GAS leads to the production of autoreactive antibodies and T cells that cross-react with host tissues4 such as human cardiac myosin, tropomyosin and laminin,5 leading to rheumatic heart disease (RHD).6–8 Anti-endothelial cell autoantibodies, which infiltrate the valve surface endothelium, are thought to play a prominent role in cardiac tissue damage in RHD.8