Abstract
Whether Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) temporally associated with SARS-CoV-2 infection are two distinct syndromes or part of the same spectrum is not fully understood. In this report, we present the case of a five-year-old boy who fully satisfied the diagnostic criteria for both KD and MIS-C associated with SARS-CoV-2 infection. He tested positive for SARS-CoV-2 on an oropharyngeal swab antigen test approximately four weeks before the onset of symptoms. He had severe abdominal pain. Abdominal ultrasound showed ascites. He improved with initial (2 g/kg) and additional (1 g/kg) intravenous immunoglobulin (IVIG) therapy and intravenous methylprednisolone (initial dose, 2 mg/kg/day). Our case may lead to clarification of the pathogenesis of both diseases. Additionally, the recent history of SARS-CoV-2 infection for children with prolonged fever and no clear focus of infection should be checked, and, if present, clinicians should consider MIS-C temporally associated with SARS-CoV-2 infection. IVIG therapy is important for children with MIS-C who meet the diagnostic criteria for KD, even if diagnosed with MIS-C.