Background: Several cases of rheumatoid arthritis (RA) with myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated crescentic glomerulonephritis (CrGN) have been reported. However, its clinical characteristics are not clear.
Methods: We summarized 3 patients of concurrent RA and MPO-ANCA-associated CrGN, diagnosed in our hospital from 1992 to 2006, and compared their clinicopathological data with those of 10 MPO-ANCA-associated CrGN patients without RA in the same period.
Results: All three RA patients were middle-aged or young adult women with 7-14 years of RA history. The initial clinical symptom was microhematuria, and mean duration from hematuria onset to histological confirmation of CrGN was 17 months. At renal biopsy, serum creatinine concentration (sCr) was modestly elevated, with the mean value of 3.4 mg/dl. Crescents were detected in 30% of glomeruli, whereas advanced glomerular sclerosis, tubular atrophy, and interstitial fibrosis were also observed. In comparison with patients without RA, patients with RA were significantly younger and showed a longer duration from the onset to histological confirmation of CrGN. Serum creatinine concentration at referral was significantly lower; however, estimated glomerular filtration rate (eGFR) was comparable. The Birmingham Vasculitis Activity Score and the Disease Extent Index were significantly lower, and pathological examination showed less crescent formation and a tendency to advanced glomerular sclerosis in patients with RA.
Conclusions: In patients with RA, MPO-ANCA-associated CrGN appeared to develop at younger ages and often showed a slowly progressive deterioration of the renal function with slight extrarenal manifestations. These smoldering clinical features may result in late referral from rheumatologists to nephrologists and therefore poor prognosis.