PADI4 and myocarditis: This review summarizes the role of neutrophil secretion, phagocytosis and their relationship in myocarditis, and discusses the function of certain agents, such as chemokine antagonists, midkine blockers and neutrophil peptidyl arginine deiminase 4 (PAD4) inhibitors in inhibiting neutrophil secretion and phagocytosis, to provide perspective for myocarditis treatments through the inhibition of neutrophil secretion and phagocytosis.