Glomerular thrombi in renal allografts associated with cyclosporin treatment

We have found glomerular capillary thrombi or afferent arteriolar thrombosis in eight renal biopsy specimens from seven renal allograft recipients. All patients were receiving cyclosporin and prednisolone. Biopsies were performed either routinely one and four weeks after transplantation or during periods of renal dysfunction. None of the patients whose biopsy material contained glomerular thrombi was considered, in retrospect, to have been undergoing rejection at the time of biopsy. Thrombi consisted of finely granular material partially obstructing glomerular capillaries. By light microscopy the staining characteristics of the thrombi were compatible with platelet-fibrin aggregates, and this was confirmed by immunoperoxidase examination. Such thrombi have not previously been seen in biopsy material from patients treated with prednisolone and azathioprine, except rarely associated with acute vascular injection. In none of these patients was there haematological evidence of the haemolytic uraemic syndrome as has been reported in bone marrow recipients treated with cyclosporin.