Analysis of renal pathology and drug history in 158 Japanese patients with rheumatoid arthritis.

To clarify the characteristics of renal pathology and its correlation with disease-modifying antirheumatic drugs (DMARDs) in patients with rheumatoid arthritis (RA), renal biopsy findings from 158 Japanese RA patients with urinary abnormalities and/or renal dysfunction were analyzed retrospectively in the period between 1979 and 1996. Urologic abnormality and urinary tract infection were ruled out in all patients. Light and immunofluorescence (IF) microscopy were performed in all patients. Mesangial proliferative glomerulonephritis (MesPGN) was diagnosed in 54 patients, membranous nephropathy (MN) in 49, and secondary amyloidosis (AM) in 30. Renal dysfunction was more frequent in patients with AM (22/30) than in patients without (40/128). Forty of 49 MN patients developed renal disorders during DMARDs therapy. The prevalence of DMARD-related MN increased during the period of observation. The fact that DMARDs are of very frequent use in recent Japanese RA patients may reflect the prevalence of MN in this study. Two thirds of patients with MesPGN developed renal disorders when no DMARDs were used. One half of 54 MesPGN patients demonstrated IgA glomerulonephritis (GN) by IF. The prevalence of primary renal diseases in Japan may reflect the frequency of IgA GN in Japanese RA patients. Furthermore, diffuse thinning of the glomerular basement membrane (GBM) was observed in 30 of 81 patients with electron microscopy. RA itself may underlie the pathogenesis of GBM thinning, and drugs used for RA treatment may also accelerate the development of this lesion. In conclusion, although MesPGN, MN, and AM may be relatively more common, IgA GN and GBM thinning also were other frequent entities in Japanese RA patients. No correlation was observed between DMARDs and renal disorders excepting MN.