Cardiology Letters 2026, 35(2):113-117

Acute perimyocarditis as the initial manifestation of adult-onset Still's disease

Luís Cotrim¹, António Carvalho¹, Mariana Gaspar², Mariana Marques Silva², Pedro Custódio¹

Cardiologia, Hospital Vila Franca de Xira, Estrada Carlos Lima Costa Nº2, 2600-009 Vila Franca de Xira, Lisboa, Portugal

Adult-onset Still's disease (AOSD) is a rare systemic autoinflammatory disorder characterized by quotidian high-spiking fever, inflammatory arthralgia, and an evanescent salmon-coloured rash. Cardiac involvement is uncommon but may include pericarditis and, less frequently, myocarditis. We report the case of an 18-year-old male presenting with persistent fever, myalgias, and arthralgia. Laboratory investigation demonstrated markedly elevated C-reactive protein (CRP 419 mg/L) and increased high-sensitivity cardiac troponin T (10511 ng/L). Electrocardiography showed sinus tachycardia with T-wave inversion in the inferolateral leads, and transthoracic echocardiography revealed a small posterior pericardial effusion without ventricular dysfunction. A diagnosis of noncomplicated acute perimyocarditis was established, and anti-inflammatory therapy was initiated. During hospitalization, recurrent high-grade fever spikes were associated with progression of an evanescent maculopapular rash and dynamic troponin variation. Marked hyperferritinaemia (11495 µg/L) was subsequently documented. Extensive infectious and autoimmune evaluation was unremarkable. The constellation of clinical and laboratory findings fulfilled classification criteria for AOSD. High-dose intravenous methylprednisolone led to rapid clinical and biochemical improvement. Corticosteroids were gradually tapered, and adalimumab was introduced as a steroid-sparing strategy, with no recurrence during follow-up. This case highlights acute perimyocarditis as a potential initial manifestation of AOSD and underscores the importance of considering systemic autoinflammatory disorders in patients presenting with inflammatory myopericardial syndromes and persistent systemic inflammation.

Keywords: Adult-onset Still's disease; Perimyocarditis; Hyperferritinaemia; Autoinflammatory disease

Published: February 1, 2026  Show citation