Objectives: Antineutrophil cytoplasmic antibody (ANCA) may appear in the course of rheumatic diseases (RD) but the kidney involvement is very rare and the prognosis poorly defined.
Methods: We retrospectively identified patients with RD among 153 patients with ANCA glomerulonephritis (ANCA-GN). Their clinical/histological presentation and outcome were compared with that of primitive ANCA-GN patients (1:4) matched for sex, age, ANCA type and follow-up.
Results: Nine patients (5.9%) were included: three had rheumatoid arthritis, two systemic sclerosis, two psoriatic arthritis, one ankylosing spondylitis and one seronegative spondylarthritis. Seven patients were MPO positive, two PR3 positive. ANCA-GN developed 74 months after RD with microscopic haematuria and acute kidney dysfunction in all but two patients. After 68-month follow-up, four patients (44.4%) achieved response to therapy defined as eGFR >60/min/1,73 m2 or stable, no microscopic haematuria and negative ANCA. At ANCA-GN diagnosis, serum creatinine and C-reactive protein were significantly lower in RD-ANCA-GN (2.38 vs. 3.34mg/dl, p=0.05 and 2.3mg/dl vs. 7.2mg/dl; p=0.05, respectively) while haemoglobin was higher (12.3g/dl vs. 9.3g/dl p<0.01) than in the 36 primitive ANCA-GN patients of control group. At kidney biopsy, focal forms were more frequent in RD patients (44.45% vs. 18.75%, p=0.11). The treatment between the two groups was not significantly different. At last observation, the percentage of patients with ESKD was lower in RD than in controls (11.1%vs. 30.5%; p=0.23).
Conclusions: Patients with RD seem to develop ANCA-GN with less severe clinical/histological kidney involvement, and better long-term kidney survival than primitive ANCA-GN. This is probably due to the strict monitoring of RD patients that allows a prompter ANCA-GN diagnosis and treatment.