Conclusions
This report describes 2 cases of MIS-C within 1 week of receiving the first dose of BNT162b2. There is no specific test for MIS-C; although both patients met diagnostic criteria, alternative diagnoses were possible. Patient 2 had costovertebral angle tenderness, unilateral renal enlargement, and 10,000 CFU/mL growth of a uropathogen on culture. Given the low level of bacterial growth, lack of enhancement on her CT, and constellation of lab and imaging abnormalities not commonly seen with urinary tract infections, MIS-C remains her most likely diagnosis.
Patient 1 had a positive antinucleocapsid antibody suggesting community-acquired COVID-19 infection before MIS-C developed (P.D. Burbelo et al., unpub. data, https://doi.org/10.1101/2020.04.20.20071423). Salzman et al. describe 3 similar cases in which MIS or an MIS-like illness developed after COVID-19 vaccination, particularly in the setting of community-acquired COVID-19.[3] The chronology of events in these cases raises the possibility that vaccination may be involved in the pathogenesis of MIS-C when preceded by community-acquired SARS-CoV-2.
The pathogenesis of MIS-C is thought to involve immune dysregulation and hyperinflammation.[4] Studies have identified high levels of receptor-binding protein (RBD) antibodies in children with severe MIS-C.[5,6] Both natural SARS-CoV-2 infection and BNT162b2 vaccination have been shown to elicit RBD antibodies.[7]It may be possible that the immune responses to these 2 forms of exposure to SARS-CoV-2 interact to shape the manifestations of mild MIS-C in the postinfectious period of COVID-19.
