A retrospective study on outcome of microscopic polyangiitis in chronic renal replacement therapy

Pauci-immune vasculitis is a heterogeneous disorder with an unfavourable prognosis. Renal involvement is frequently observed in antineutrophil cytoplasm autoantibody (ANCA)-associated small-vessel vasculitis and is an important cause of end-stage renal disease (ESRD). Renal replacement therapy (RRT) is frequently required. Although better prognosis under dialysis is well known, the long-term follow-up of pauci-immune renal vasculitis with RRT is rarely reported.

We described 24 patients with pauci-immune vasculitis and requirement of dialysis who were admitted in our institutions from January 1989 to December 2008. Mean age was 65 ± 12 years at the beginning of dialysis. There were 12 males and 12 females. Patients with Wegener's granulomatosis, Churg-Strauss syndrome or evidence of anti-glomerular basement membrane were excluded. The study group was formed by patients with a diagnosis of necrotizing extracapillary glomerulonephritis and microscopic polyangiitis.

The distribution according to ANCAs was 14 p-ANCA (58%), 5 c-ANCA (21%) and 5 ANCA-negative (21%) pauci-immune renal vasculitis. Pulmonary renal syndrome (PRS) was observed in 10 patients at the onset of vasculitis. Corticosteroids and daily cyclophosphamide were administered to 18 patients, and one patient had intravenous cyclophosphamide. Five patients received isolated corticosteroid therapy. Early reduction in cyclophosphamide dosage was required in five patients due to leucopaenia. Mean follow-up after first dialysis was 89 ± 66 months (range 2-208). Twenty patients were included in haemodialysis (HD), and four patients were included in peritoneal dialysis (PD). At the end of the study, nine patients had received a cadaveric kidney transplant (KT). Relapses rate after the onset of dialysis was 0.03 episode/patient/year. PRS-associated relapses after beginning dialysis were observed in four patients. Main therapy in relapses was also corticosteroids and cyclophosphamide. Survival rates for year 1, 2 and 5 was 91%, 91% and 85%, respectively. Overall mortality at the end of the study was 31.8%. Five patients died in the PRS group, but only one death was associated with progressive pulmonary fibrosis. Higher mortality was observed in PRS vasculitis present at the onset of RRT (50% vs 16.7%, P = NS). Better outcome in patients who received a renal transplantation was observed (88.8% vs 53.8%, P = NS). Conclusions. Despite a low number of patients in this series, pauci-immune vasculitis prognosis under dialysis seems equal to other causes of chronic kidney disease. This study observed a low rate of relapses after beginning dialysis. Poor prognosis is related to severe complications at the beginning of RRT. Today, kidney transplantation is an important therapeutic option for these patients.