PRTN3 and granulomatosis with polyangiitis: A recent genome-wide association study (GWAS) of 2687 Northern European Caucasian patients with GPA and MPA suggested that GPA is associated with genetic variants within HLA-DP, SERPINA1 (encoding α1-antitrypsin), and PRTN3 (encoding PR3), whereas MPA is mainly associated with HLA-DQ [16].