Multisystem Inflammatory Syndrome in an Adult Following COVID-19 mRNA Vaccination: Successful Treatment With Medium-Dose Steroids and Colchicine.

Multisystem inflammatory syndrome in children and adults (MIS-C/A) was rarely reported as a complication of coronavirus disease 2019 (COVID-19) and potential adverse events following COVID-19 vaccination. Recently, the case definition of MIS-C/A was developed by the Brighton Collaboration Network. However, only a limited number of adult patients with MIS-A following immunization have been reported, and there is still little evidence for adequate treatment. A 57-year-old man presented with fever, headache, vomiting, and hypotension 24 days after receiving the second COVID-19 vaccination with the Pfizer-BioNTech vaccine. According to the Brighton Collaboration Case Definition, the patient met a definitive case of MIS-A after vaccination (level 1 of diagnostic certainty). After administration of medium-dose prednisolone (20 mg/d) with colchicine (1.2 mg/d), all symptoms and signs improved rapidly. The dose of prednisolone was gradually tapered from the third week, and the patient confirmed a full recovery without medication after 8 weeks. This is the first report showing that low-dose steroids in combination with colchicine may be an effective treatment option for MIS-A after vaccination.