The diagnosis of AAV involves a comprehensive approach that includes clinical manifestations, serologic testing [immunoassays for PR3‐ANCAs and MPO-ANCAs, eosinophils, exclusion of anti–glomerular basement membrane disease and systemic lupus erythematosus (SLE)] and when feasible tissue biopsy. The gene discussed is PRTN3; the disease is systemic lupus erythematosus.