Interstitial inflammatory and chronic tubulointerstitial lesions in lupus nephritis: comparison with those in IgA nephropathy.

The significance of interstitial inflammatory and chronic tubulointerstitial lesions was studied in relation to the severity of glomerular lesions in 62 patients with lupus nephritis and 88 with IgA nephropathy. Severe interstitial inflammatory and chronic tubulointerstitial lesions were found in patients with severe glomerular lesions in both lupus nephritis and IgA nephropathy. In such cases, the serum creatinine levels at biopsy were high and the renal prognosis was poor regardless of the underlying disease (lupus nephritis or IgA nephropathy). No IgA nephropathy patients with nil or mild glomerular lesions had moderate or severe interstitial inflammatory and/or chronic tubulointerstitial lesions. In contrast, predominantly severe interstitial inflammatory lesions were found in 36% of lupus nephritis patients with nil or mild glomerular lesions. The prevalence of interstitial immune complexes deposition was markedly high in those with predominant interstitial inflammatory lesions. However, the severity of chronic tubulointerstitial lesions was mild and renal function did not deteriorate in the mean follow-up periods of 68.6 months. It is suggested that, besides the tubulointerstitial lesions attributable to the severe concomitant glomerular damage, the interstitial deposition of immune complexes per se plays a pathogenic role in the interstitial inflammatory lesions in lupus nephritis. Its prognostic significance, however, was considered to be minor.