Renal involvement in rheumatoid arthritis: analysis of renal biopsy specimens from 100 patients

We analyzed renal biopsy specimens from 100 patients to evaluate the characteristics of renal involvement in patients with rheumatoid arthritis (RA). Membranous nephropathy (MN) was the most common renal histological pattern (31%). Mesangial proliferative glomerulonephritis (GN) was found in 21% of cases (IgA nephropathy 12%, non-IgA GN 9%), minor changes in 17%, renal amyloidosis in 11%, interstitial nephritis in 9%, sclerotic GN in 4%, and crescentic GN in 2%. MN was relatively more frequent in men than in women, and most developed nephrotic syndrome, while a few developed renal failure. Disease-modifying antirheumatic drugs (DMARDs) correlated with MN in 26 of 31 cases. Mesangial proliferative GN showed high-grade hematuria. Amyloidosis correlated with long duration of RA; approximately half of the cases with amyloidosis also had nephrotic syndrome, and 82% developed renal failure. Of the 100 patients, 82% showed some tubulo-interstitial changes, which might be related to non-steroidal anti-inflammatory drugs. Because renal lesions in RA are very diverse, and early stage cases of MN and amyloidosis can be detected only by histological examinations, renal biopsy should be performed in cases with continuous urinary abnormalities or progressive renal failure.