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Abstract: SA-PO837

Interstitial Fibrosis in ANCA-Associated Vasculitis: Myeloperoxidase (MPO) vs. PR3

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis


  • Marco, Helena, Fundacio Puigvert, Barcelona, Catalunya, Spain
  • Vilardell, Jordi, Fundacio Puigvert, Barcelona, Catalunya, Spain
  • Silva, Irene, Fundacio Puigvert, Barcelona, Catalunya, Spain
  • Bardaji de Quixano, Beatriz, Fundacio Puigvert, Barcelona, Catalunya, Spain
  • Diaz Encarnacion, Montserrat M., Fundacio Puigvert, Barcelona, Catalunya, Spain

Group or Team Name

  • Group of Renal Inflammatory Diseases (GERI).

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a necrotizing vasculitis characterized by inflammation of small blood vessels, being the kidney one of the most frequently affected organs. AAV has a high morbidity and mortality rate, leading to rapidly progressive renal failure that may lead to end-stage kidney disease. Its pathogenesis is a complex and multifactorial process involving inflammation and fibrosis. PR3-AAV and MPO-AAV have clinical-demographic differences and different renal phenotypes observed in kidney biopsy. The histopathological subgrouping into four classes (focal, crescentic, mixed, and sclerotic) is useful for predicting long-term renal survival, the worst being sclerotic class.
Our aim is to determine whether interstitial fibrosis in AAV is at least as important as glomerular sclerosis in prognosis.


Retrospective single-center study of 95 AAV patients (78 MPO-AAV and 17 PR3-AAV) diagnosed by renal biopsy, with at least 1-year follow-up. Type of ANCA, immunosuppressant therapy and renal/patient survival were evaluated. Histomorphometric quantification using MetaMorph® software on trichrome-stained biopsies slides to measure the degree of fibrosis.
Data analysis performed under standard conditions.


PR3-AAV population was predominantly male (70%, mean age=62, mean follow-up=54 months), while MPO-AAV population was mainly female (65.8%, mean age=66, follow-up=65 months).
There were no statistically significant differences in renal function between MPO and PR3-AAV at diagnosis. Albeit renal function improved throughout follow-up in MPO (p<0.01) and PR3-AAV (p=0.05), MPO-AAV showed worse renal function than PR3-AAV (p=0.01) at the end of follow-up.
MPO-AAV showed more interstitial fibrosis at diagnosis than PR3-AAV (p=0.01). However, there were no significant differences in the incidence of glomerulosclerosis (p=0.26). PR3-AAV showed more crescentic proliferation (p=0.03) but less fibrotic crescents than MPO-AAV at diagnosis.


The method we used allows a quantitative assessment of renal fibrosis. Our data confirm that renal prognosis is better in PR3-AAV than in MPO-AAV. This could be explained by a greater interstitial fibrosis, as well as more fibrotic crescentic in MPO-AAV at diagnosis.