#1356 Kidney phenotype in interstitial lung disease associated with ANCA-vasculitis: European Multicentre Study

Abstract Background and Aims Interstitial lung disease (ILD) in ANCA-associated vasculitis (AAV) has the appearance of a progressive fibrotic disease on imaging and primarily affects the interstitial lung compartment and is usually associated with MPO-ANCA. Whether patients with AAV-ILD display a similar fibrotic pattern in their kidneys is unclear. Method A European multicentre retrospective study included patients with AAV-ILD. The diagnosis of ILD was confirmed by a CT chest pattern of usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), organising pneumonia or chronic hypersensitivity pneumonia. We aimed to determine if kidney involvement in AAV-ILD exhibited a more fibrotic pattern compared to AAV-related nephritis without ILD, using data from the Cambridge AAV cohort. Results 135 patients with AAV-ILD were included; 94 (70%) had also kidney involvement, in whom the mean age was 71 ± 11 years and 87% MPO-ANCA positive. The ILD diagnosis preceded AAV in 17%, 64% presented concurrently with kidney involvement, 20% with pulmonary haemorrhage. The most common lung radiological pattern was UIP (67%). At presentation, the median glomerular filtration rate (GFR) was 27 ml/min per 1.73 m2 (interquartile range 12-50), with a median albumin-to creatinine ratio 23 mg/mmol (IQR 10-97). Among 72 patients with available kidney biopsy, the most prevalent Berden class was focal in 45%, followed by mixed in 33%, crescentic in 18% and sclerotic in 4%. Although, the prevalence of Berden classes did not significantly differ between ILD-nephritis and no ILD-nephritis groups, the former group had a higher baseline GFR (p = 0.05), lower albuminuria level (p = 0.002), higher percentage of normal glomeruli (p = 0.027), lower glomerular necrosis percentage (p = 0.002) and higher interstitial fibrosis score (p = 0.049). Within five years, the ILD-nephritis group demonstrated renal recovery, as indicated by an adjusted mean delta GFR of 13.4 ml/min per 1.73 m2, without a significant difference compared to the no ILD-nephritis group. Over a median follow-up of 4.9 years (IQR 2-9), the progression to end-stage kidney disease (ESKD) was comparable between the groups. However, notably, the ILD-nephritis group experienced significantly poorer survival rates (mean 10.9 years vs 17.9 years, log-rank p 0.001). Conclusion In AAV-ILD, kidney involvement is often characterized by fewer inflammatory and a higher prevalence of fibrotic lesions than on non-ILD-AAV. Despite initial differences in renal pathology and kidney function between these groups, both demonstrated similar risks of progressing to ESKD. Nevertheless, it's crucial to underscore the significant influence of ILD on the overall outcomes of AAV patients with kidney involvement.