The Multifaceted Presentation of the Multisystem Inflammatory Syndrome in Children: Data from a Cluster Analysis.

Background: The aim of this study was to evaluate the outcomes of patients with the multisystem inflammatory syndrome in children (MIS-C) according to phenotypes of disease and define the prognostic factors for the severe course. Methods: This cross-sectional study included 293 patients with MIS-C from seven pediatric rheumatology centers. A two-step cluster analysis was performed to define the spectrum of disease and their outcomes were compared between each group. Results: Four subgroups were identified as follows: cluster I, predominantly Kawasaki-like features (n = 100); cluster II, predominantly MAS-like features (n = 34); cluster III, predominantly LV dysfunction (n = 47); cluster IV, other presentations (n = 112). The duration of fever was longer in cluster II and the length of hospitalization was longer in both clusters II and III. Laboratory findings revealed lower lymphocyte and platelet counts and higher acute phase reactants (APRs) in cluster II, while patients in cluster IV showed less inflammation with lower APRs. The resolution of abnormal laboratory findings was longer in clusters II and III, while it was shortest in cluster IV. Seven patients died. Among them, four belonged to cluster II, while three were labeled as cluster III. Patients with severe course had higher levels of neutrophil-lymphocyte ratio, mean platelet volume, procalcitonin, ferritin, interleukin-6, fibrinogen, D-Dimer, BNP, and troponin-I, and lower levels of lymphocyte and platelet counts. Conclusion: As shown, MIS-C is not a single disease presenting with various clinical features and outcomes. Understanding the disease spectrum will provide individualized management