Renal histopathology in kidney transplant recipients immunosuppressed with cyclosporin A: results of an international workshop.

Kidney transplant biopsies from 55 patients immunosuppressed with cyclosporin A and 35 treated with conventional immunosuppression were evaluated by 14 pathologists. In cyclosporin treated cases the following morphologic features were more frequent and/or severe: isometric tubular vacuolization; tubular microcalcification, tubular atrophy, interstitial fibrosis striped form, focal interstitial infiltrates and arteriolopathy. Six different morphologic reaction patterns in cyclosporin treated patients were distinguished and possible pathogenetic factors discussed: 1. Classical rejection, 2. Diffuse interstitial fibrosis, 3. Toxic tubulopathy with giant mitochondria, isometric vacuolization and microcalcification, 4. Peritubular capillary congestion with mononuclear cell accumulation, 5. Arteriolopathy similar to benign/malignant hypertension or hemolytic uremic syndrome, 6. Interstitial fibrosis (striped form) with tubular atrophy. This preliminary morphologic classification may be helpful in the biopsy interpretation and the selection of therapeutic strategies and should stimulate further studies.