Our observation that an association between platelets, kidney injury and complement C3 is not present in disease controls (IgA nephropathy, diabetic kidney disease, and acute interstitial nephritis) and specifically observed in the MPO-ANCA subgroup implicates distinct pathomechanisms dependent on seropositivity for MPO-ANCA or PR3-ANCA. This evidence concerns the gene C3 and IgA glomerulonephritis.