In 65% (13/20), the myocardial involvement met the diagnostic criteria for the multisystem inflammatory response syndrome associated with SARS-CoV-2 (i.e., pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2; PIMS-TS), and in 20% (4/20), we identified specific IgA and IgM antibodies for Coxsackie B1, B2, and B3 and enteroviruses. This evidence concerns the gene CD79A and COVID-19–associated multisystem inflammatory syndrome in children.