To determine if common indicators of inflammation (blood cell counts, ESR, CRP, Hb) and S100A12 correlate with disease activity over the course of CPV, we analyzed a total of 117 serum samples obtained concurrent with clinical data from 56 children with systemic vasculitis; 48 samples were collected at times likely to correspond to high disease activity (diagnosis and flare), and 69 samples at follow up visits when disease activity should be reduced. This evidence concerns the gene GSTM1 and necrotizing vasculitis.