MPO and granulomatosis with polyangiitis: Among patients receiving a clinical diagnosis of GPA, those positive for MPO-ANCAs more frequently have limited disease without severe organ involvement, a higher prevalence of subglottic stenosis, a less frequent need for cyclophosphamide or rituximab therapy and fewer relapses than patients who are positive for PR3ANCA.20,21 These data indicate that ANCA specificity is a major determinant of the clinical presentation in AAV.