Objectives We assessed the frequency, clinical features and prognosis of renal involvement in granulomatosis with polyangiitis (GPA) and current treatment approaches.

Methods We performed a retrospective analysis of 234 patients with GPA, diagnosed according to Chapel-Hill Consensus Conference 2012 classification, 81 male and 153 female, aged 53 (41; 62) years. 54 patients (23.1%) had localized GPA. 174 (74.4%) were ANCA positive. Median follow up was 61.5 (32; 105) months. 103 patients (44%) had a history of renal involvement. Frequencies of proteinuria, hematuria, hypertension, rapidly progressive glomerulonephritis (RPGN), acute kidney injury (AKI) and chronic kidney disease (CKD) grades were analyzed.

Results In 25 patients (24.3% of 103) renal involvement developed at disease onset, the other 78 patients (75.7%) developed glomerulonephritis after a median of 3 (1; 12) months. Hematuria was present in 94 (91.3%), proteinuria in 85 patients (82.5%), nephrotic syndrome in 11 patients (10.7%), hypertension in 31 patients (30.1%). Rapidly progressive glomerulonephritis (RPGN) defined by the doubling of serum creatinine within ≤3 months developed in 29 patients (28.2% of 103). Myeloperoxidase-ANCA-positive patients (n=12) developed RPGN significantly more often than proteinase-3-ANCA-positive patients (n=78): 7 (58.3%) vs 22 (28.2%) (p=0.0499). 11 (10.7%) patients developed AKI, stage 3 being the most common (in 8 patients). 40 (38.8%) patients exhibited indolent renal disease course, i.e. without worsening of renal function. By the end of the follow-up, 33 (32.0%) patients were diagnosed with CKD grade 3b-5, among them 11 patients (10.7%) developed end-stage renal disease (ESRD). 6 patients (5.8%) died. As the first line induction therapy all patients received corticosteroids in combination with cyclophosphamide in 93 patients (90.3%), rituximab (RTX) in 3 patients (2.9%), mycophenolate mofetil in 7 patients (6.8%). RTX was used for remission induction in 27 (26.2%) patients due to refractory or recurrent disease. During follow-up, 74 patients (71.8%) developed one or more severe relapses with a relapse rate of 0.27 per patient-year. 50 (48.5%) patients had renal relapses (0.096 per patient-year).

Conclusions Prevalence of renal involvement in the studied group was lower than expected, most likely because of a large proportion of patients with localized GPA. Our study showed that RPGN was not the most common feature of renal involvement. Almost 40% of patients developed indolent course of kidney disease. Nevertheless one third of patients developed CKD G3B or worse by the end of the follow up. Despite effective induction therapy with high-dose corticosteroids, cytotoxic agents and/or RTX relapses, both renal and extrarenal, are frequent.

Disclosure of Interest None declared