1. Anti-PTX3 antibodies were detected in 29.7% AAV patients, significantly more common in EGPA (44.7% vs. 25 and 19%). 2. The presence of anti-PTX3 was associated with a lower prevalence of systemic, ENT, and renal manifestations. 3. Among ANCA negative patients, 35.7% displayed positive anti-PTX3 antibodies. 4. The prevalence of anti-PTX3 antibodies was significantly higher in AAV patients than in healthy controls and other CDT patients, but lower than in SLE. The gene discussed is PTX3; the disease is systemic lupus erythematosus.