Post-COVID multisystem inflammatory syndrome: diagnostic dilemmas outside the COVID-19 pandemic - a clinical case of therapeutic success

Abstract

Background: Pediatric Multisystem Inflammatory Syndrome associated with SARS-CoV-2 (MIS-C) is a rare complication that typically develops between two to six weeks after infection. It is characterized by a hyperinflammatory state with a well-established pathophysiological basis. Although its incidence has declined since the peak of the COVID-19 pandemic, MIS-C should still be considered in the differential diagnosis of pediatric patients presenting with systemic inflammation. Case Presentation:We describe the case of a 4-year-old girl with a nine-day history of upper respiratory tract symptoms, followed by mucocutaneous, systemic, and respiratory manifestations. Laboratory findings showed elevated acute-phase reactants, coagulation abnormalities with increased D-dimer levels, and positive COVID-19 IgG antibodies. The patient had not received prior COVID-19 vaccination. Based on WHO, CDC, and RCPCH criteria, the case was classified as Multisystem Inflammatory Syndrome associated with SARS-CoV-2. Management and Outcome: Treatment included immunomodulatory therapy with intravenous human immunoglobulin and corticosteroids, resulting in a favorable clinical response. Inflammatory markers progressively decreased, and the described symptoms resolved. Anticoagulation and thromboprophylaxis were adjusted according to thrombotic risk and coagulation parameters. The patient showed favorable clinical evolution without target organ involvement and an overall good prognosis. Conclusion: Maintaining clinical suspicion and ensuring early diagnosis of MIS-C are crucial for timely initiation of immunomodulatory therapy. Despite its current low incidence, MIS-C should remain an important consideration in the differential diagnosis of pediatric patients with compatible clinical findings.