Acute cardiac complication in a patient with antimitochondrial M2 antibody-positive myositis on immunosuppressive therapy.

As the emerging disease concept of antimitochondrial M2 antibody (AMA-M2)-positive myositis gains wider recognition, reports of its cardiac complications are increasing. However, the clinical course and optimal management of cardiac involvements in patients with AMA-M2-positive myositis remain unclear. We report the case of a 53-year-old male with AMA-M2-positive myositis who had been receiving immunosuppressive therapy for four years. He presented with cardiogenic shock with an atypical clinical course that responded to corticosteroid pulse therapy. This case report provides valuable insights into the clinical course and potential treatment option for cardiac involvement in patients with AMA-M2-positive myositis. Learning objectives: This case highlights the unique clinical course of cardiac involvement in a patient with antimitochondrial M2 antibody-positive myositis under long-term immunosuppressive therapy, and suggests the potential efficacy of corticosteroid pulse therapy in the setting of acute exacerbations. Physicians should consider abrupt cardiac complications even during maintenance therapy. Rapid recognition and aggressive steroid treatment may yield favorable outcomes even in these complex cases.