PRTN3 and necrotizing vasculitis: It is also important to note that some IgG4-RD patients may present with weakly positive ANCA, potentially linked to widespread immune system activation.[13] Although this patient had positive IgM rheumatoid factor and PR3-ANCA, kidney biopsy did not show necrotizing vasculitis or crescent formation, and clinical symptoms such as nasal destruction and lung cavitation, typical of granulomatosis with polyangiitis, were absent, thus excluding the diagnosis of ANCA-associated vasculitis.