Transplant capillaropathy and transplant glomerulopathy: ultrastructural markers of chronic renal allograft rejection.

A late dysfunction of a renal allograft refers to a progressive decline in renal function manifested)3 months after transplantation. A late dysfunction may have several causes, such as chronic rejection, chronic allograft nephropathy, chronic calcineurin inhibitor toxicity, de novo or recurrent renal disease and acute rejection. An allograft biopsy is necessary to establish a definitive diagnosis. The standard interpretation of alterations is widely carried out on the basis of the ‘Banff 97 classification’, which relies on the evaluation of light microscopic stains [1]. The assessment of allograft biopsies by light microscopy per se, however, is hampered by the fact that the histological examination of the specimen is not sufficient to identify all types of rejection. Whereas acute cellular rejection can be appropriately diagnosed, the recognition of chronic rejection seems impossible in a certain number of cases involving chronic rejection, and the verification of an alloantibody-mediated graft injury requires the application of immunohistochemistry [2,3]. Renal capillary lesions attributed to chronic rejection have recently been described ultrastructurally. The present communication reviews these markers, and demonstrates how the incorporation of electron microscopy into the evaluation of allograft biopsies with a late dysfunction can help the pathologist establish the proper diagnosis.