Acute Severe Myocarditis as the Presenting Complaint of Adult-Onset Still's Disease: A Case Report

Abstract

Adult-onset Still’s disease (AOSD) is a rare systemic autoinflammatory condition characterised by a classical triad of symptoms: prolonged fever, polyarthritis, and a characteristic salmon-pink skin rash. It can affect a variety of organ systems, resulting in many different clinical presentations. Myocarditis complicated by cardiogenic shock is a rare and life-threatening manifestation of AOSD, typically affecting younger patients. There is limited experience and evidence in how to best manage this challenging patient cohort. Case: A previously fit and healthy 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 magnetic resonance imaging findings were in keeping with fulminant myocarditis. Further septic and autoimmune screens were negative, although he responded well to high-dose intravenous corticosteroids. Attempts to wean immunosuppression were unsuccessful. His ferritin was markedly elevated (20,233 ug/L), prompting haematological and rheumatological opinions. A diagnosis of AOSD was suspected using Yamaguchi criteria. The successful addition of tocilizumab (an interleukin-6 receptor antagonist) therapy enabled gradual de-escalation of steroid therapy with ongoing disease remission at 6 months. This case highlights the importance of considering AOSD as a rare cause of 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 being an effective treatment option.