These features in association with positivity for c-ANCA and the presence of anti-proteinase 3 antibodies at high titre (39 U/mL; reference 0–5 U/mL), alongside negative cultures for microorganisms of the patient's CSF, blood, urine, and other potential sources of infection, confirmed the diagnosis of GPA [6, 7]. Here, PRTN3 is linked to granulomatosis with polyangiitis.