Studies have also demonstrated a higher frequency of Z-allele carriers in Caucasian GPA cohorts.18, 19, 20, 21 More recently, two Genome-Wide Association Studies (GWAS) confirmed the association between SERPINA1 SNPs with AAV, especially GPA and anti-PR3 antibody positivity.8 This evidence concerns the gene PRTN3 and granulomatosis with polyangiitis.