MP204
SLOWLY PROGRESSIVE GLOMERULONEPHRITIS IN PATIENTS WITH ANCA ASSOCIATED VASCULITIS (AAV)

INTRODUCTION AND AIMS: Renal involvement in anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is common and usually occurs in 70% of patients with granulomatosis with polyangiitis(GPA) and in almost 100% of patients with microscopic polyangiitis (MPA). Renal involvement in AAV is characterized by rapidly progressive renal failure and histologically by necrotizing crescentic glomerulonephritis. Anecdotal cases of AAV with slower progression to end-stage renal disease (ESRD) have been reported. The purpose of this study is to describe a particular subset of AAV patients with slow renal progression.

METHODS: We included patients with a diagnosis of AAV, classified as GPA or MPA using the ACR 1990criteria and/or 2012 Chapel Hill Consensus Conference definitions, whose renal involvement was characterized by slow progression, i.e. reduction of eGFR > 60 mL/min to < 30 mL/min over at least 9 months. All patients had to have a sufficient renal follow-up before and after AAV diagnosis (> 12 months prior to and > 12 months after diagnosis); the pre-diagnosis observation was required to confirm the slow disease progression.

RESULTS: A total of 25 patients were identified by searching the AAV databases of 5 different centres. At first detection of pathological eGFR values, all patients had urinary abnormalities (e.g. hematuria and proteinuria). The median time from the first pathological eGFR value to AAV diagnosis was 13 months (IQR 9-34). At diagnosis, the median age was 72 years (IQR 67-79), the median creatinine 3.4 mg/dL (IQR 2.1-4.5). 25/25 patients were P-ANCA and/or MPO-ANCA positive. 9/25 patients had interstitial lung lesions and 3/25 had peripheral neuropathy. Only 2 patients had alveolar hemorrhage. AAV-related glomerulonephritis was histologically confirmed in 15/25 patients. 9/15 patients had a sclerotic form and 6/15 had a mixed form according to Berden’s classification; no case was classified as focal or crescentic; no one had fibrinoid necrosis. At diagnosis 5/25 patients had ESRD requiring dialysis, and 20/25 had varying degrees of renal failure. 21/25 patients received immunosuppression (5/21 steroid therapy, 5/21 steroids plus conventional immunosuppressive drugs, 11/21 rituximab). Twelve months after diagnosis, 10 of the 21 treated patients had renal function improvement, 5/21 had stable renal function and 2/21 worsened renal function.

CONCLUSIONS: A subset of AAV has a slowly progressive course. This subset usually has an MPA phenotype, is MPO-ANCA positive and has few extra-renal manifestations except for a high prevalence of interstitial lung disease. Renal histology usually shows sclerotic or mixed phenotypes. Treatment of this patient subset may dampen progression of AAV-related renal disease.