Although the exact mechanism of viral pericarditis—whether by direct viral replication or indirectly by autoimmune or autoinflammatory mechanism—can be difficult to establish, in our series, parvovirus B19 was the likely etiology for pericarditis in patients 1 and 2 given the preceding viral illness, positive parvovirus B19 serology (including IgM antibodies), and subsequent pericarditis. Here, CD40LG is linked to pericarditis.