This mutant recognized as many ANCA serum samples from patients with GPA as the wild-type human PR3-Val103 in both immunofluorescence assay and enzyme-linked immunosorbent assay (ELISA), while the Ser195Ala mutation is close to Epitope 5 of PR3 and remote from Epitopes 1, 3, and 4 as shown in Figure 1 (8, 11). This evidence concerns the gene PRTN3 and granulomatosis with polyangiitis.