A 17-Year-Old Boy with Chest Pain

This Case Records article describes a 17-year-old male with chest pain, syncope, and elevated cardiac biomarkers, initially diagnosed with myopericarditis. Despite symptom resolution after NSAIDs, recurrent episodes over 9.5 months revealed muscle weakness, persistent inflammation, and biochemical signs of myositis. Extensive testing ruled out infectious causes and supported an autoimmune origin. Laboratory studies showed markedly elevated antinuclear antibody (ANA) titers and positive anti-U1-ribonucleoprotein (RNP) and anti-Smith antibodies. Cardiac MRI confirmed myocardial and pericardial inflammation; echocardiography revealed concentric LV hypertrophy. The evolving clinical picture myopericarditis, myositis, Raynaud-like features, and hypertension was diagnosed as undifferentiated autoimmune rheumatic disease, consistent with mixed connective-tissue disease. Management included corticosteroids, rituximab, and mycophenolate sodium. The article emphasizes the importance of integrating cardiac, rheumatologic, and immunologic findings in adolescents with persistent systemic inflammation and overlapping autoimmune phenotypes.

This Case Records article describes a 17-year-old male with chest pain, syncope, and elevated cardiac biomarkers, initially diagnosed with myopericarditis. Despite symptom resolution after NSAIDs, recurrent episodes over 9.5 months revealed muscle weakness, persistent inflammation, and biochemical signs of myositis. Extensive testing ruled out infectious causes and supported an autoimmune origin. Laboratory studies showed markedly elevated antinuclear antibody (ANA) titers and positive anti-U1-ribonucleoprotein (RNP) and anti-Smith antibodies. Cardiac MRI confirmed myocardial and pericardial inflammation; echocardiography revealed concentric LV hypertrophy. The evolving clinical picture myopericarditis, myositis, Raynaud-like features, and hypertension was diagnosed as undifferentiated autoimmune rheumatic disease, consistent with mixed connective-tissue disease. Management included corticosteroids, rituximab, and mycophenolate sodium. The article emphasizes the importance of integrating cardiac, rheumatologic, and immunologic findings in adolescents with persistent systemic inflammation and overlapping autoimmune phenotypes.