A rare presentation of acute myocarditis as a manifestation of adult-onset Still's disease: a case report.

Background: Adult-onset Still's disease (AOSD) is a rare systemic autoinflammatory condition characterized by a classical triad of symptoms that include prolonged fever, polyarthritis, and a characteristic salmon-pink skin rash. It can affect a variety of organ systems resulting in many different clinical presentations and is usually a diagnosis of exclusion. Myocarditis complicated by cardiogenic shock is a rare and life-threatening manifestation of AOSD, typically affecting younger patients. There is a limited experience and evidence in how best to manage this challenging patient cohort. Case summary: A previously fit and well 22-year-old male presented with fever, arthralgia, and general malaise. On clinical examination, he was pyrexial and hypotensive, requiring vasopressor support for presumed septic shock. Subsequent transthoracic echocardiography and cardiac MRI findings were in keeping with fulminant myocarditis. Further septic and auto-immune screens were negative although he responded well to high-dose intravenous corticosteroids. Attempts to wean immunosuppression were unsuccessful, and his ferritin was markedly elevated (20 233 μg/L). A diagnosis of AOSD was suspected after exclusion of other possible causes. The successful addition of tocilizumab (an interleukin-6 receptor antagonist) therapy allowed for gradual de-escalation of steroid therapy and disease remission, with on-going remission at 18 months on maintenance therapy. Discussion: This case highlights the importance of considering AOSD as a rare cause for myocarditis, especially when fever is present, or disease is severe. Failure to improve with first-line therapy involving high-dose corticosteroids, or inability to wean that therapy, should prompt consideration for escalation of therapy, with tocilizumab seemingly an effective treatment option.