The clinical and pathological characteristics of nephropathies in connective tissue diseases in the Japan Renal Biopsy Registry (J-RBR)

Background: In connective tissue diseases, a wide variety of glomerular, tubulointerstitial, and vascular lesions of the kidney are observed. Nonetheless, recent information is limited regarding renal lesions in connective tissue diseases, except in systemic lupus erythematosus (SLE). Methods: In this study, we used a nationwide database of biopsy-confirmed renal diseases in Japan (J-RBR) (UMIN000000618). In total, 20,523 registered patients underwent biopsy between 2007 and 2013; from 110 patients with connective tissue diseases except SLE, we extracted data regarding the clinico-pathological characteristics of the renal biopsy. Results: Our analysis included patients with rheumatoid arthritis (RA) (n = 52), Sjögren’s syndrome (SjS) (n = 35), scleroderma (n = 10), mixed connective tissue disease (MCTD; n = 5), anti-phospholipid syndrome (APS; n = 3), polymyositis/dermatomyositis (PM/DM; n = 1), Behçet’s disease (n = 1) and others (n = 3). The clinico-pathological features differed greatly depending on the underlying disease. The major clinical diagnosis was nephrotic syndrome in RA; chronic nephritic syndrome with mild proteinuria and reduced renal function in SjS; rapidly progressive nephritic syndrome in scleroderma. The major pathological diagnosis was membranous nephropathy (MN) and amyloidosis in RA; tubulointerstitial nephritis in SjS; proliferative obliterative vasculopathy in scleroderma; MN in MCTD. In RA, most patients with nephrosis were treated using bucillamine, and showed membranous nephropathy. Conclusions: Using the J-RBR database, our study revealed that biopsy-confirmed cases of connective tissue diseases such as RA, SjS, scleroderma, and MCTD show various clinical and pathological characteristics, depending on the underlying diseases and the medication used.