The fact that GAS is antigenically complementary to CX, that laminin is complementary to collagen IV, that myosin is complementary to actin, and that all six are known targets of autoantibodies in RHD/AM, suggests that beyond MM, the role of antigenic complementarity in the pathogenesis of autoimmune forms of carditis must also be considered. The gene discussed is MYH14; the disease is rheumatic heart disease.