Autoimmunity Against the Heart and Cardiac Myosin in Children With Myocarditis.

•Levels of antibodies to cardiac myosin in children with clinical myocarditis were higher than in control children.•Neither antibody levels at initial presentation or at follow-up corresponded to recovery of normal cardiac function according to echocardiography.•Antibody-mediated activation of protein kinase A was higher at presentation in children with myocarditis who did not recover by 12 months after diagnosis.•Differences in antibody-mediated cell signaling, rather than just antibody levels, may play a role in cellular damage and possibly outcomes in children with myocarditis.