Distinct clinical and immunological features of SARS-COV-2-induced multisystem inflammatory syndrome in children.

Background Pediatric SARS-CoV-2 infection can be complicated by a dangerous hyperinflammatory condition termed multisystem inflammatory syndrome in children (MIS-C). The clinical and immunologic spectrum of MIS-C and its relationship to other inflammatory conditions of childhood have not been studied in detail. Methods We retrospectively studied confirmed cases of MIS-C at our institution from March to June 2020. The clinical characteristics, laboratory studies and treatment response were collected. Data were compared with historic cohorts of Kawasaki disease (KD) and macrophage activation syndrome (MAS). Results Twenty-eight patients fulfilled the case definition of MIS-C. Median age at presentation was 9 years (range 1 month to 17 years); 50% of patients had pre-existing conditions. All patients had laboratory confirmation of SARS-CoV-2 infection. Seventeen patients (61%) required intensive care, including 7 patients (25%) requiring inotrope support. Seven patients (25%) met criteria for complete or incomplete KD and coronary abnormalities were found in 6 cases. Lymphopenia, thrombocytopenia, and elevation in inflammatory markers, D-dimer, B-type natriuretic peptide, IL-6 and IL-10 levels were common but not ubiquitous. Cytopenias distinguished MIS-C from KD and the degree of hyperferritinemia and pattern of cytokine production differed between MIS-C and MAS. Immunomodulatory therapy given to MIS-C patients included IVIG (71%), corticosteroids (61%) and anakinra (18%). Clinical and laboratory improvement were observed in all cases, including 6 cases that did not require immunomodulatory therapy. No mortality was recorded in this cohort. Conclusion MIS-C encompasses a broad phenotypic spectrum with clinical and laboratory features distinct from Kawasaki disease and macrophage activation syndrome. Funding This work was supported by the National Institute of Health / National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) K08-AR074562 (PYL), K08-AR AR073339 (LAH), R01-AR065538, R01-AR073201 and P30-AR070253 (PAN); National Institute of Allergy and Infectious Diseases 5T32AI007512-34 (JL, JR, TB, AAN and RWN); Rheumatology Research Foundation Investigator Awards (PYL and LAH) and Medical Education Award (JSH); Boston Children's Hospital Faculty Career Development Awards (PYL and LAH), the McCance Family Foundation (JWN), and the Samara Jan Turkel Center (JC, RPS, MBS).