Fulminant myocarditis in a young woman with mixed connective tissue disease: a case report.

Background: Although cardiac involvement is relatively common in mixed connective tissue disease (MCTD), few reports on MCTD-associated fulminant myocarditis are available.

Case Summary: A 22-year-old woman diagnosed with MCTD was admitted to our institution for cold-like symptoms and chest pain. Echocardiography revealed that the left ventricular ejection fraction (LVEF) had rapidly decreased from 50 to 20%. Because endomyocardial biopsy revealed no significant lymphocytic infiltration, immunosuppressant drugs were not started initially; however, steroid pulse therapy (methylprednisolone, one1000 mg/day) was initiated due to prolonged symptoms and unimproved haemodynamics. Despite strong immunosuppressant therapy, the LVEF did not improve, and severe mitral regurgitation appeared. Three days after steroid pulse therapy initiation, she experienced a sudden cardiac arrest; thus, venoarterial extracorporeal membrane oxygenation (VA-ECMO) and intra-aortic balloon pumping (IABP) were initiated. Subsequent immunosuppressant therapy was continued with prednisolone (100 mg/day) and intravenous cyclophosphamide (1000 mg). Six days after steroid therapy initiation, the LVEF improved to 40% and then recovered to near-normal levels. After successful weaning off of VA-ECMO and IABP, she was discharged. Thereafter, a detailed histopathological examination revealed multi-focal signs of ischaemic micro-circulatory injury and diffuse HLA-DR in the vascular endothelium, suggesting an autoimmune inflammatory response.

Discussion: We report a rare case of fulminant myocarditis in a patient with MCTD who recovered with immunosuppressive treatment. Despite the absence of significant lymphocytic infiltration findings on histopathological examination, patients with MCTD may experience a dramatic clinical course. Although it is unclear whether myocarditis is triggered by viral infections, certain autoimmune mechanisms may lead to its development.