Emerging phenotypes in kidney transplant rejection

Purpose of reviewThis review focuses on more recently emerging rejection phenotypes in the context of time post transplantation and the resulting differential diagnostic challenges. It also discusses how novel ancillary diagnostic tools can potentially increase the accuracy of biopsy-based rejection diagnosis.Recent findingsWith advances in reducing immunological risk at transplantation and improved immunosuppression treatment renal allograft survival improved. However, allograft rejection remains a major challenge and represent a frequent course for allograft failure. With prolonged allograft survival, novel phenotypes of rejection are emerging, which can show complex overlap and transition between cellular and antibody-mediated rejection mechanisms as well as mixtures of acute/active and chronic diseases. With the emerging complexity in rejection phenotypes, it is crucial to achieve diagnostic accuracy in the individual patient.SummaryThe prospective validation and adoption of novel molecular and computational diagnostic tools into well defined and appropriate clinical context of uses will improve our ability to accurately diagnose, stage, and grade allograft rejection.