Spectrum of cytomegalovirus-induced renal pathology in renal allograft recipients

Viral infections in renal allograft recipients constitute an important cause of renal graft dysfunction. They have shown an increasing incidence coinciding with more potent immunosuppression regimens. Cytomegalovirus (CMV) is well-known cause of a tubulointerstitial nephritis rich in plasma cells with cytopathic changes in tubular epithelial and endothelial cells. However, involvement of glomeruli and larger arteries in the absence of tubulointerstitial disease is rare. In this study, we demonstrated the spectrum of renal disease caused by CMV among renal allograft recipients. Retrospective analysis of 2900 renal allograft biopsies performed over a 10-year period revealed 10 cases of CMV infection, with half of them (5/10) detected in 2010-2011. Although tubulointerstitial nephritis due to CMV was the most common lesion (7/10), we noted an increased incidence of CMV glomerulopathy with (1/10) or without (3/10) coexisting tubulointerstitial CMV disease. Isolated glomerular involvement was characterized by a relative lack of inflammation in any of the compartments along with the presence of cytopathic changes in the glomerular endothelial cells and podocytes. Another patient had CMV-induced thrombotic microangiopathy. The coexistent diseases were calcineurin inhibitor toxicity (n = 1), antibody-mediated rejection (n = 1), cellular rejection (n = 2), and invasive fungal infection (n = 1). In conclusion, there is a wide spectrum of CMV-induced lesions. CMV glomerulopathy is characterized by cytopathic changes in glomerular endothelial cells and podocytes with a lack of significant inflammation. In contrast, CMV-induced arteriopathy can present as thrombotic microangiopathy. Coinfection with other pathogens like invasive fungi can lead to graft failure.