De novo post-transplant thrombotic microangiopathy localized only to the graft in autosomal dominant polycystic kidney disease with thrombophilia

Introduction: Thrombotic microangiopathy (TMA) is a serious complication of renal transplantation and is mostly related to the prothrombotic effect of calcineurin inhibitors (CNIs). A subset of TMA (29%-38%) is localized only to the graft. Case 1: A young woman suffering from autosomal dominant polycystic kidney disease (ADPKD) underwent kidney transplant. After 2 months, she showed slow renal deterioration (serum creatinine from 1.9 to 3.1 mg/dl), without hematological signs of hemolytic-uremic syndrome (HUS); only LDH enzyme transient increase was detected. Renal biopsy showed TMA: temporary withdraw of tacrolimus and plasmapheresis was performed. The renal function recovered (serum creatinine 1.9 mg/dl). From screening for thrombophilia, we found a mutation of the Leiden factor V gene. Case 2: A man affected by ADPKD underwent kidney transplantation, with delay graft function; first biopsy showed acute tubular necrosis, but a second biopsy revealed TMA, while no altered hematological parameters of HUS was detected. We observed only a slight increase of lactate dehydrogenase (LDH) levels. The tacrolimus was halved and plasmapheresis was performed: LDH levels normalized within 10 days and renal function improved (serum creatinine from 9 to 2.9 mg/dl). We found a mutation of the prothrombin gene. Only a renal biopsy clarifies the diagnosis of TMA, but it is necessary to pay attention to light increasing level of LDH. Conclusion: Prothrombotic effect of CNIs and mTOR inhibitor, mutation of genes encoding factor H or I, anticardiolipin antibodies, vascular rejection, cytomegalovirus infection are proposed to trigger TMA; we detected mutations of factor II and Leiden factor V, as facilitating conditions for TMA in patients affected by ADPKD.