Similarly, another exome sequencing study17 identified defects in XIAP (OMIM 300079) and CYBB (OMIM 300481) in 3 of 18 sequenced patients with MIS-C, whereas RNA sequencing of patients with MIS-C revealed dysregulated cytotoxic lymphocyte responses to SARS-CoV-2 infection as major drivers.18 These genetic studies suggest dysregulation of the inflammatory response as a characteristic of MIS-C, although they were limited to a small number of patients who were mostly of European origin. Here, CYBB is linked to COVID-19–associated multisystem inflammatory syndrome in children.