Prolonged Fever and Multisystem Hyperinflammation in an Adolescent Following SARS-CoV-2 Exposure: An Atypical Multisystem Inflammatory Syndrome-Like Presentation

Abstract

Prolonged fever with multisystem inflammation in adolescents poses a significant diagnostic challenge, especially during the viral season. Multisystem inflammatory syndrome in children (MIS-C) is a post-infectious inflammatory condition that may mimic bacterial sepsis, systemic rheumatologic disease, oncohematologic processes, or postviral dysregulation. We present a case of a 13-year-old, previously healthy boy with hectic fever, severe myalgia, and pharyngitis accompanied by elevated inflammatory markers. The clinical course was characterized by persistent fever unresponsive to broad-spectrum antibiotics, Synovitis of the knees and hips, respiratory distress with radiographic evidence of pneumonia, pericardial effusion, and mitral valve dysfunction; laboratory values include elevated cardiac troponin levels and elevated inflammatory markers (IL-6, D-dimer, and ferritin), as well as transient liver dysfunction. SARS-CoV-2 IgG was positive. Extensive infectious, hematologic, and rheumatologic evaluation was unrevealing. The patient demonstrated rapid clinical and laboratory improvement following treatment with intravenous methylprednisolone and immunoglobulin. Although the clinical picture was most compatible with MIS-C or a MIS-C-like post-SARS-CoV-2 hyperinflammatory syndrome, atypical features, including predominant respiratory involvement, gradual progression, and absence of shock, suggested a broader disease spectrum. This case highlights the diagnostic challenges of post–COVID-19 hyperinflammatory syndromes, which may present with overlapping features of infection and immune-mediated diseases.