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Kidney Week

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

Authors

  • 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).
Background

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.

Methods

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.

Results

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.

Conclusion

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.