Objectives Childhood-onset systemic lupus erythematosus (cSLE) is a multisystemic autoimmune disease characterized by inflammatory organ damage by means of vasculitis. Pentraxin-3 (PTX3) is expressed locally at the sites of inflammatory processes, predominantly from endothelial cells. In adult studies, PTX3 has shown to be an indicator of active vasculitis both in large-vessel and small-vessel vasculitides, as well as in SLE. Moreover, in SLE it has found to be correlated with disease activity, and with some of the clinical manifestations and laboratory parameters. We aimed to ascertain if PTX3 might be a significant mediator in cSLE and if it might indicate active vasculitis during the course of the disease.