To determine if kidney disease trajectories differ between MPO-ANCA and PR3-ANCA-seropositive participants matched for kidney function at diagnosis, we evaluated the change in eGFR from diagnosis to follow-up at 6 and 12 months in participants with normal to mildly reduced kidney function (KDIGO stages 1–2), moderately reduced kidney function (KDIGO stage 3) and severely reduced kidney function to kidney failure (KDIGO stages 4–5) at diagnosis. This evidence concerns the gene MPO and kidney disorder.