Going Beyond the Glomerulus in ANCA Vasculitis

Document Type

Conference Proceeding

Publication Date

4-2024

Publication Title

American Journal of Kidney Diseases

Abstract

Isolated tubulointerstitial involvement may represent a novel subtype of renal involvement in ANCA-associated vasculitis(AAV). A 71 yo male with history of HTN and BPH presented with bilateral lower extremity edema, myalgias, unintentional weight loss (15 lbs) for 6 months. He later developed severe dyspnea prompting admission. Initial exam also showed a new non-pruritic purpuric rash on bilateral ankles. Initial labs showed normocytic anemia, mild leukocytosis and S.Cr 3.47 (baseline of 1.1-1.5 two months ago). UA showed 3-5 RBCs/HPF without any dysmorphic RBCs or erythrocyte casts. Spot UPCR was elevated at 380mg/g. Ultrasound of the kidneys and bladder was unremarkable. Given concern for RPGN, he underwent further workup with complement levels and other serologies including ANA and anti-GBM Ab which were normal. CANCA titers were noted to be elevated (1:320). Anti-MPO Ab were also detected. Biopsy showed acute tubulointerstitial nephritis with moderate interstitial fibrosis and tubular atrophy, without glomerular hypercellularity, crescents, thrombi or necrosis. He was treated with pulse dose steroids and rituximab and symptoms subsequently improved with continued immunosuppression. Reduction in c-ANCA and anti-MPO Ab titers was also noted. At 2 months follow up, patient was noted to be doing well with stabilization of S.Cr to 2.7-2.8 and improvement in spot UPCR to 200 mg/g. The current classification of renal involvement in AAV is primarily based on glomerular lesions. However, isolated tubulointerstitial involvement has been increasingly reported. Many hypotheses about pathogenesis(peritubular capillaritis, extravascular granulomas, lysis of the tubular basement membrane) have been proposed. It is mostly seen in elderly population and most exhibit variable levels of MPOANCA positivity. Relatively lower levels of S.Cr elevation, proteinuria and hematuria are seen. Prior to making a diagnosis, other causes of AIN like allergic reaction, infection and drug toxicity must be excluded. Immunosuppression has proven to be effective in majority of cases. Given rising incidence of isolated tubulointerstitial involvement in AAV, further research is needed due to lack of unified diagnostic criteria, prognostic indicators and treatment strategies

Volume

83

Issue

4 Suppl 2

First Page

S12

Comments

National Kidney Foundation 2024 Spring Clinical Meetings, May 14-18, 2024, Long Beach, CA

DOI

10.1053/j.ajkd.2024.01.042

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