Pathologic changes in the renal tubule in systemic lupus erythematosus

Interstitial nephritis may be prominent morphologic feature in systemic lupus erythematosus (SLE), but there are limited data relating the pathologic findings to renal function impairment. We studied 69 biopsy specimens from 55 patients by light, fluorescence, and electron microscopy and compared the results with the serum creatinine levels. The relative interstitial volume, a measure of tubular damage and interstitial expansion, was the only morphologic feature that correlated well with renal function (serum creatinine level). Fifty-nine per cent of the biopsy specimens studied by fluorescence microscopy and 31 per cent of the biopsy specimens studied by electron microscopy had extraglomerular deposits. Ultrastructural studies determined that the sites of the deposits were the tubular basal lamina in five cases, the peritubular capillaries in four, and both in 12. In addition, the deposits were irregularly deposited along the nephron, with examples of isolated proximal and distal tubular involvement. Ultrastructural changes in the tubular basal lamina were interpreted as reparative responses to injury. Tubular pathologic features included reduplicated basal lamina and the apparent incorporation of electron-dense deposits and cellular debris. These data support the concept of a role for immune deposits in the pathogenesis of the tubulointerstitial lesion in SLE.