Thrombotic microangiopathy after kidney transplantation

De novo thrombotic microangiopathy after kidney transplantation in adults: Interplay between complement genetics and multiple endothelial injury

De novo thrombotic microangiopathy (dnTMA), after renal transplantation may significantly alter graft outcomes. However, its pathogenesis and the role of complement alternative pathway dysregulation remain elusive. We studied all consecutive adult patients with a kidney allograft biopsy performed between January 2004 and March 2016 displaying dnTMA. Ninety-two patients were included. The median time of occurrence was 166 (IQR 25-811) days. The majority (82.6 %) had TMA localized only in the graft. Calcineurin inhibitor toxicity and antibody-mediated rejection (ABMR) were the 2 most frequent causes (54.3% and 37.0%, respectively). However, etiological factors were multiple in 37% patients. Interestingly, pathogenic variants in the genes of complement alternative pathway were significantly more frequent in the 42 tested patients than in healthy controls (16.7% vs 3.7% respectively, P < .008). The overall graft survival after biopsy was 66.0% at 5 years and 23.4% at 10 years, significantly worse than a matched cohort without TMA. Moreover, graft survival of patients with TMA and ABMR was worse than a matched cohort with ABMR without TMA. The 2 main prognostic factors were a positive C4d staining and a lower estimated glomerular filtration rate at diagnosis. DnTMA is a severe and multifactorial disease, induced by 1 or several endothelium-insulting conditions, mostly calcineurin inhibitor toxicity and ABMR.

Thrombotic microangiopathy after kidney transplantation: Expanding etiologic and pathogenetic spectra

Thrombotic microangiopathy (TMA) is an uncommon but serious complication that not only affects native kidneys but also transplanted kidneys. This review is specifically focused on post-transplant TMA (PT-TMA) involving kidney transplant recipients. Its reported prevalence in the latter population varies from 0.8% to 14% with adverse impacts on both graft and patient survival. It has many causes and associations, and the list of etiologic agents and associations is growing constantly. The pathogenesis is equally varied and a variety of patho genetic pathways lead to the development of microvascular injury as the final common pathway. PT-TMA is categorized in many ways in order to facilitate its management. Ironically, more than one causes are contributory in PT-TMA and it is often difficult to pinpoint one particular cause in an individual case. Pathologically, the hallmark lesions are endothelial cell injury and intravascular thrombi affecting the microvasculature. Early diagnosis and classification of PT-TMA are imperative for optimal outcomes but are challenging for both clinicians and pathologists. The Banff classification has addressed this issue and has developed minimum diagnostic criteria for pathologic diagnosis of PT-TMA in the first phase. Management of the condition is also challenging and still largely empirical. It varies from simple maneuvers, such as plasmapheresis, drug withdrawal or modification, or dose reduction, to lifelong complement blockade, which is very expensive. A thorough understanding of the condition is imperative for an early diagnosis and quick treatment when the treatment is potentially effective. This review aims to increase the awareness of relevant stakeholders regarding this important, potentially treatable but under-recognized cause of kidney allograft dysfunction.

TMA in Kidney Transplantation

Thrombotic microangiopathy (TMA) is a rare and devastating complication of kidney transplantation, which often leads to graft failure. Posttransplant TMA (PT-TMA) may occur either de novo or as a recurrence of the disease. De novo TMA can be triggered by immunosuppressant drugs, antibody-mediated rejection, viral infections, and ischemia/reperfusion injury in patients with no evidence of the disease before transplantation. Recurrent TMA may occur in the kidney grafts of patients with a history of atypical hemolytic uremic syndrome (aHUS) in the native kidneys. Studies have shown that some patients with aHUS carry genetic abnormalities that affect genes that code for complement regulators (CFH, MCP, CFI) and components (C3 and CFB), whereas in 10% of patients (mostly children), anti-FH autoantibodies have been reported. The incidence of aHUS recurrence is determined by the underlying genetic or acquired complement abnormality. Although treatment of the causative agents is usually the first line of treatment for de novo PT-TMA, this approach might be insufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve kidney function. Targeted complement inhibition is an effective treatment for recurrent TMA and may be effective in de novo PT-TMA as well, but it is necessary to establish which patients can benefit from different therapeutic options and when and how these can be applied.

Haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is a heterogeneous group of diseases that result in a common pathology, thrombotic microangiopathy, which is classically characterised by the triad of non-immune microangiopathic haemolytic anaemia, thrombocytopenia, and acute kidney injury. In this Seminar, different causes of HUS are discussed, the most common being Shiga toxin-producing Escherichia coli HUS. Identifying the underlying thrombotic microangiopathy trigger can be challenging but is imperative if patients are to receive personalised disease-specific treatment. The quintessential example is complement-mediated HUS, which once carried an extremely high mortality but is now treated with anti-complement therapies with excellent long-term outcomes. Unfortunately, the high cost of anti-complement therapies all but precludes their use in low-income countries. For many other forms of HUS, targeted therapies are yet to be identified.

Delayed Graft Function in Kidney Transplant: Risk Factors, Consequences and Prevention Strategies

Background. Delayed graft function is a frequent complication of kidney transplantation that requires dialysis in the first week posttransplant. Materials and Methods. We searched for the most relevant articles in the National Institutes of Health library of medicine, as well as in transplantation, pharmacologic, and nephrological journals. Results. The main factors that may influence the development of delayed graft function (DGF) are ischemia–reperfusion injury, the source and the quality of the donated kidney, and the clinical management of the recipient. The pathophysiology of ischemia–reperfusion injury is complex and involves kidney hypoxia related to the duration of warm and cold ischemia, as well as the harmful effects of blood reperfusion on tubular epithelial cells and endothelial cells. Ischemia–reperfusion injury is more frequent and severe in kidneys from deceased donors than in those from living donors. Of great importance is the quality and function of the donated kidney. Kidneys from living donors and those with normal function can provide better results. In the peri-operative management of the recipient, great attention should be paid to hemodynamic stability and blood pressure; nephrotoxic medicaments should be avoided. Over time, patients with DGF may present lower graft function and survival compared to transplant recipients without DGF. Maladaptation repair, mitochondrial dysfunction, and acute rejection may explain the worse long-term outcome in patients with DGF. Many different strategies meant to prevent DGF have been evaluated, but only prolonged perfusion of dopamine and hypothermic machine perfusion have proven to be of some benefit. Whenever possible, a preemptive transplant from living donor should be preferred.

Rejection-associated Phenotype of De Novo Thrombotic Microangiopathy Represents a Risk for Premature Graft Loss

Supplemental Digital Content is available in the text.

Background.

Thrombotic microangiopathy (TMA) significantly affects kidney graft survival, but its pathophysiology remains poorly understood.

Methods.

In this multicenter, retrospective, case–control paired study designed to control for donor-associated risks, we assessed the recipients’ risk factors for de novo TMA development and its effects on graft survival. The study group consists of patients with TMA found in case biopsies from 2000 to 2019 (n = 93), and the control group consists of recipients of paired kidney grafts (n = 93). Graft follow-up was initiated at the time of TMA diagnosis and at the same time in the corresponding paired kidney graft.

Results.

The TMA group displayed higher peak panel-reactive antibodies, more frequent retransplantation status, and longer cold ischemia time in univariable analysis. In the multivariable regression model, longer cold ischemia times (odds ratio, 1.18; 95% confidence interval [CI], 1.01-1.39; P = 0.043) and higher peak pretransplant panel-reactive antibodies (odds ratio, 1.03; 95% CI, 1.01-1.06; P = 0.005) were found to be associated with increased risk of de novo TMA. The risk of graft failure was higher in the TMA group at 5 y (hazard ratio [HR], 3.99; 95% CI, 2.04-7.84; P < 0.0001). Concomitant rejection significantly affected graft prognosis at 5 y (HR, 6.36; 95% CI, 2.92-13.87; P < 0.001). De novo TMA associated with the active antibody-mediated rejection was associated with higher risk of graft failure at 5 y (HR, 3.43; 95% CI, 1.69-6.98; P < 0.001) compared with other TMA.

Conclusions.

Longer cold ischemia and allosensitization play a role in de novo TMA development, whereas TMA as a part of active antibody-mediated rejection was associated with the highest risk for premature graft loss.

Clinical profile and outcomes of De novo posttransplant thrombotic microangiopathy

Thrombotic microangiopathy (TMA) after kidney transplant is rather uncommon but an important reversible cause of graft loss. This retrospective study of biopsy-proven posttransplant TMA was done to identify the important etiological factors, clinical features, and outcomes of post transplant TMA in a tertiary care referral hospital in northern India. This retrospective study was conducted among all renal transplant recipients who presented with graft dysfunction between 1989 and 2015. All the cases were looked for their etiology, clinical course, treatment modalities, and renal outcomes. The study was conducted in accord with prevailing ethical principles and reviewed by our own institutional review board. Seventeen patients out of 2000 (0.008%) transplants done during the study period had posttransplant TMA, out of which all the patients had de novo TMA, and the median time of presentation after transplantation was four months. Systemic TMA was noted in only four patients. Biopsy revealed associated rejection in five patients and associated calcineurin inhibitor (CNI) toxicity in 12 patients. Patients with TMA due to CNI toxicity were managed with CNI reduction or switching to alternate CNI or mammalian target of rapamycin inhibitors. In addition, antithymocyte globulin and plasma exchange were used in rejection-associated TMA. While four out of 12 patients (33%) in CNI-related TMA developed end-stage renal disease (ESRD), all patients in rejection-associated TMA developed ESRD. The overall one-year graft survival was 47%, whereas five- and 10-year survival was 35%. There was no significant difference in graft survival between localized and systemic TMAs (P = 0.4). Posttransplant TMA should be suspected even if there are no systemic features of hemolysis and early graft biopsy and prompt action is needed. The occurrence of TMA in the setting of rejection is associated with grave prognosis.

Haematological disorders following kidney transplantation

Transplantation offers cure for some haematological cancers, end-stage organ failure, but at the cost of long-term complications. Renal transplantation is the best-known kidney replacement therapy and it can prolong end-stage renal disease patient lives for decades. However, patients after renal transplantation are at a higher risk of developing different complications connected not only with surgical procedure but also with immunosuppressive treatment, chronic kidney disease progression and rejection processes. Various blood disorders can develop in post-transplant patients ranging from relatively benign anaemia through cytopenias to therapy-related myelodysplasia and acute myeloid leukaemia (AML) and post-transplant lymphoproliferative disorders followed by a rare and fatal condition of thrombotic microangiopathy and haemophagocytic syndrome. So far literature mainly focused on the post-transplant lymphoproliferative disease. In this review, a variety of haematological problems after transplantation ranging from rare disorders such as myelodysplasia and AML to relatively common conditions such as anaemia and iron deficiency are presented with up-to-date diagnosis and management.

Characteristics, management and outcomes of atypical haemolytic uraemic syndrome in kidney transplant patients: a retrospective national study

Background

Kidney transplantation (KTx) is a strong trigger for the development of either recurrent or de novo atypical haemolytic uraemic syndrome (aHUS). According to previous studies, eculizumab (ECU) is effective for prophylaxis and for treatment of recurrence.

Methods

We evaluated the experiences of Spanish patients with recurrent and de novo aHUS associated with KTx, treated or not treated with ECU. In the de novo group, we classified patients as having early de novo (during the first month) or late de novo aHUS (subsequent onset).

Results

We analysed 36 cases of aHUS associated with KTx. All of the 14 patients with pre-KTx diagnosis of aHUS were considered to have high or moderate risk of recurrence. Despite receiving grafts from suboptimal donors, prophylactic ECU was effective for avoiding recurrence. The drug was stopped only in two cases with low–moderate risk of recurrence and was maintained in high-risk patients with no single relapse. There were 22 de novo aHUS cases and 16 belonged to the early de novo group. The median time of onset in the late group was 3.4 years. The early group had a better response to ECU than the late group, probably due to earlier diagnosis and use of the drug. No genetic pathogenic variant was detected in de novo aHUS cases, suggesting a secondary profile of the disease. ECU was stopped in all de novo patients with no relapses. ECU was well tolerated in all cases.

Conclusions

Both groups (pre-aHUS and de novo) presented different clinical profiles, management approaches and outcomes. One should consider aHUS regardless of time after KTx. Genetic studies are crucial to stratify risks of relapse and to determine necessary lengths of treatment. We suggest short ECU treatment for de novo cases without pathogenic mutation and that ECU treatment be considered pre-emptively for patients with moderate or high risk of recurrence.

Consensus regarding diagnosis and management of atypical hemolytic uremic syndrome

Thrombotic microangiopathy (TMA) is defined by specific clinical characteristics, including microangiopathic hemolytic anemia, thrombocytopenia, and pathologic evidence of endothelial cell damage, as well as the resulting ischemic end-organ injuries. A variety of clinical scenarios have features of TMA, including infection, pregnancy, malignancy, autoimmune disease, and medications. These overlapping manifestations hamper differential diagnosis of the underlying pathogenesis, despite recent advances in understanding the mechanisms of several types of TMA syndrome. Atypical hemolytic uremic syndrome (aHUS) is caused by a genetic or acquired defect in regulation of the alternative complement pathway. It is important to consider the possibility of aHUS in all patients who exhibit TMA with triggering conditions because of the incomplete genetic penetrance of aHUS. Therapeutic strategies for aHUS are based on functional restoration of the complement system. Eculizumab, a monoclonal antibody against the terminal complement component 5 inhibitor, yields good outcomes that include prevention of organ damage and premature death. However, there remain unresolved challenges in terms of treatment duration, cost, and infectious complications. A consensus regarding diagnosis and management of TMA syndrome would enhance understanding of the disease and enable treatment decision-making.

Metastatic lung adenocarcinoma- associated thrombotic microangiopathy in a renal transplant recipient

Thrombotic microangiopathy (TMA) after renal transplantation can be a diagnostic challenge. TMA can occur with calcineurin inhibitors, allograft rejection, infection, mutations in complement regulatory proteins and autoimmunity. A 52-year-old male renal transplant recipient presented with extensive deep vein thrombosis. He developed transfusion-dependent microangiopathic haemolytic anaemia with thrombocytopenia. He did not respond calcineurin inhibitor cessation, eculizumab or plasma exchange. ADAMTS13 and complement levels were normal. Infection and autoimmune screens were negative. A diagnosis of metastatic adenocarcinoma was made on bone marrow biopsy. This represents a rare case of malignancy-associated TMA in a renal transplant recipient. Early diagnosis can facilitate the prompt initiation of chemotherapy which is the only treatment option.

Renal Complications Following Lung Transplantation and Heart Transplantation

Renal complications are common following heart and/or lung transplantation and lead to increased morbidity and mortality. Renal dysfunction is also associated with increased mortality for patients on the transplant wait list. Dialysis dependence is a relative contraindication for heart or lung transplantation at most centers, and such patients are often listed for a simultaneous kidney transplant. Several factors contribute to the impaired renal function in patients undergoing heart and/or lung transplantation, including the interplay between cardiopulmonary and renal hemodynamics, complex perioperative issues, and exposure to nephrotoxic medications, mainly calcineurin inhibitors.

De Novo Thrombotic Microangiopathy in Renal Transplant Patients

OBJECTIVES

Thrombotic microangiopathy is a form of renal capillary injury possibly associated with calcineurin inhibitor toxicity, acute humoral rejection, infections, and recurrent diseases. Here, we examined its incidence in patients diagnosed with acute and chronic active humoral rejection, polyomavirus nephropathy, acute cellular rejection, and immunoglobulin A recurrence.

MATERIALS AND METHODS

In total, 272 renal allograft recipients who met the inclusion criteria were reevaluated for presence of renal thrombotic microangiopathy. Thrombotic microangiopathy diagnosis was established by clinical, laboratory, and histologic features. C4d expression in peritubular capillaries was determined. Clinical data were collected from medical records.

RESULTS

Of 272 patients (mean age of 42.8 ± 12.7 years), only 74 patients (27.2%) had de novo thrombotic microangiopathy, which was found in 30/90 patients (33.3%) with acute humoral rejection, 9/51 (17.6%) with acute cellular rejection, 22/53 (41.5%) with chronic active humoral rejection, 10/55 (18.2%) with polyomavirus nephropathy, and 3/23 (13%) with immunoglobulin A nephropathy. Significant differences were shown between therapy type and thrombotic microangiopathy development (P = .02). Patients who received cyclosporine (38.5%) tended to show higher incidence of thrombotic microangiopathy than patients who received tacrolimus (20.7%) or sirolimus (7.7%). Patients with C4d-positive acute humoral (97.6% vs 2.4%) and chronic active humoral rejection (68.2% vs 31.8%) had greater incidence of thrombotic microangiopathy versus those who were C4d-negative. Graft loss was significantly higher in C4d-positive than in C4d-negative thrombotic microangiopathy groups (P < .001). Overall 1-, 3-, and 5-year graft survival was 94%, 85%, and 85% versus 83%, 51%, and 51% in thrombotic microangiopathy-negative versus thrombotic microangiopathy-positive patients (P < .001).

CONCLUSIONS

Acute humoral rejection and chronic active humoral rejection were the most common and therefore most important causes of de novo thrombotic microangiopathy in renal transplant patients. Its presence in the renal allograft biopsy should arouse suspicion for underlying acute or chronic active humoral rejection.

Antithymocyte globulin-induced hemolytic anemia and thrombocytopenia after kidney transplantation

Antithymocyte globulin is the most widely used lymphocyte-depleting treatment in kidney transplantation. In spite of the frequency of side effects, including anemia and thrombocytopenia, their pathophysiological mechanisms are not clearly established. Here, we report the case of a 21-year-old patient who had a first kidney transplantation and received induction immunosuppressive therapy by thymoglobulin. Immediately after kidney transplantation, he developed a severe hemolytic anemia and thrombocytopenia with a subsequent perirenal hematoma, which lead to a second surgical procedure and a transfer to the intensive care unit. Our patients' anemia and thrombocytopenia had heteroimmune characteristics, and thymoglobulin therapy was suspected to be the cause, via an interaction with a common Fc-receptor epitope in the different cell lines.

De Novo Atypical Haemolytic Uremic Syndrome after Kidney Transplantation

De novo thrombotic microangiopathy (TMA) can occur after kidney transplantation. An abnormality of the alternative pathway of complement must be suspected and searched for, even in presence of a secondary cause. We report the case of a 23-year-old female patient who was transplanted with a kidney from her mother for end-stage renal disease secondary to Hinman syndrome. Early after transplantation, she presented with 2 episodes of severe pyelonephritis, associated with acute kidney dysfunction and biological and histological features of TMA. Investigations of the alternative pathway of the complement system revealed atypical haemolytic uremic syndrome secondary to complement factor I mutation, associated with mutations in CD46 and complement factor H related protein genes. Plasma exchanges followed by eculizumab injections allowed improvement of kidney function without, however, normalization of creatinine.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

Thrombotic Microangiopathy and the Kidney

Thrombotic microangiopathy can manifest in a diverse range of diseases and is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ injury, including AKI. It can be associated with significant morbidity and mortality, but a systematic approach to investigation and prompt initiation of supportive management and, in some cases, effective specific treatment can result in good outcomes. This review considers the classification, pathology, epidemiology, characteristics, and pathogenesis of the thrombotic microangiopathies, and outlines a pragmatic approach to diagnosis and management.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Impact of treatment and outcomes for patients with posttransplant drug-associated thrombotic microangiopathy

BACKGROUND

Drug-induced transplant-associated thrombotic microangiopathy (DTA-TMA) is a rare but serious complication that can occur after hematopoietic cell transplantation (HCT) or solid organ transplantation (SOT) without guidelines for optimal management of this condition.

STUDY DESIGN AND METHODS

Given the ambiguity surrounding the treatment for DTA-TMA, we conducted a retrospective review to evaluate the impact of different treatment strategies in DTA-TMA patients. Our primary endpoint was to determine the overall response rate (ORR) for DTA-TMA based on the type of treatment modality chosen while secondary endpoints included the time to response, relapse rates, and overall survival for DTA-TMA cases.

RESULTS

There were a total of 14 DTA-TMA patients of whom nine were post-HCT and five were post-SOT. Most of the DTA-TMA cases were due to tacrolimus (n = 11) with a minority related to sirolimus (n = 3). A total of nine of 14 patients demonstrated response and five had no response to therapy. The ORR among the DTA-TMA patients after HCT and SOT who received plasma exchange (PLEX) were 25 and 100%, respectively. The ORRs among the patients (includes HCT and SOT) who received rituximab (n = 3) and eculizumab (n = 5) were 67 and 60%, respectively. There were two relapses noted in our study and both were in the HCT group.

CONCLUSION

While discontinuation of the offending agent may be sufficient for treatment of DTA-TMA after HCT, PLEX may be a reasonable option for DTA-TMA after SOT. Although the results are encouraging with rituximab and eculizumab in the treatment of DTA-TMA, larger prospective studies are needed to validate our findings.

De novo thrombotic microangiopathy following simultaneous pancreas and kidney transplantation managed with eculizumab

Thrombotic microangiopathy (TMA) is a well-recognised complication following transplantation, often due to an underlying genetic predisposition, medications or rejection. The use of eculizumab in these settings has been previously described, but its role still remains to be clarified. A 45-year-old man, with a history of type 1 diabetes mellitus and subsequent end-stage kidney failure, presented for a simultaneous pancreas-kidney transplant. Immunologically, he was well matched with the donor, and he received standard induction immunosuppression including tacrolimus. His early transplant course was complicated by Haemophilus parainfluenzae paronychia and a Pseudomonas aeruginosa catheter-associated urinary tract infection. Within 1 week, he developed thrombotic microangiopathy with significant renal dysfunction and eventual dialysis dependence, without evidence of transplant rejection on biopsy. He was also noted to have antiphospholipid antibodies in moderate titres. The TMA did not resolve despite cessation of tacrolimus, and he was subsequently commenced on eculizumab. The patient achieved a partial remission from TMA, with ongoing biochemical evidence of haemolysis, although now with stable graft function, despite significant damage. His transplanted pancreas remained seemingly unaffected by TMA, and continues to function well. This case describes an unusual presentation of TMA post-transplantation and is the only described case of eculizumab use following pancreas-kidney transplant. It remains unclear in this case what the likely precipitant for TMA was, although it seems to be, at least in part, controlled by ongoing use of eculizumab, presumably by terminal complement inhibition.

[A CASE OF SUCCESSFUL RECOVERY OF RENAL ALLOGRAFT FUNCTION FOLLOWING A DIAGNOSIS OF THROMBOTIC MICROANGIOPATHY CLINICALLY MADE IN THE IMMEDIATE POST-TRANSPLANT PERIOD]

A 57-year-old female patient on hemodialysis with chronic renal failure due to chronic glomerular nephritis received deceased donor kidney transplantation. Induction immunosuppressive therapy was combination of tacrolimus, mycophenolate mofetil, everolimus, prednisolone, and basiliximab. She was diagnosed with secondary thrombotic microangiopathy (TMA) by clinical findings such as hemolytic anemia, thrombocytopenia and acute kidney injury not by pathological findings on the 4th post-operative date. Plasma exchange was performed with suspension of tacrolimus. General conditions recovered, and the graft function was preserved.

Atypical hemolytic uremic syndrome diagnosed four years after ABO-incompatible kidney transplantation

Atypical hemolytic uremic syndrome (aHUS) in allograft kidney transplantation is caused by various factors including rejection, infection, and immunosuppressive drugs. We present a case of a 32 year old woman with aHUS four years after an ABO-incompatible kidney transplantation from a living relative. The primary cause of end-stage renal disease was unknown; however, IgA nephropathy (IgAN) was suspected from her clinical course. She underwent pre-emptive kidney transplantation from her 60 year old mother. The allograft preserved good renal function [serum creatinine (sCr) level 110-130 μmol/L] until a sudden attack of abdominal pain four years after transplant, with acute renal failure (sCr level, 385.3 μmol/L), decreasing platelet count, and hemolytic anemia with schizocytes. On allograft biopsy, there was thrombotic microangiopathy in the glomeruli, with a cellular crescent formation and mesangial IgA and C3 deposition. Microvascular inflammation, such as glomerulitis, peritubular capillaritis, and arteriole endarteritis were also detected. A disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) did not decrease and Shiga toxin was not detected. Donor-specific antibodies or autoantibodies, including anti-neutrophil cytoplasmic antibody and anti-glomerular basement membrane (anti-GBM) antibody, were negative. The patient was diagnosed with aHUS and received three sessions of plasmapheresis and methylprednisolone pulse therapy, followed by oral methylprednisolone (0.25-0.5 mg/kg) instead of tacrolimus. She temporarily required hemodialysis (sCr level, 658.3 μmol/L). Thereafter, her sCr level improved to 284.5 μmol/L without dialysis therapy. This case is clinically considered as aHUS after kidney transplantation, associated with various factors, including rejection, glomerulonephritis, and toxicity from drugs such as tacrolimus.

Safety of mTOR inhibitors in adult solid organ transplantation

INTRODUCTION

Mammalian target of rapamycin (mTOR) inhibitors (sirolimus and everolimus) are a class of immunosuppressive drugs approved for solid organ transplantation (SOT). By inhibiting the ubiquitous mTOR pathway, they present a peculiar safety profile. The increased incidence of serious adverse events in early studies halted the enthusiasm as a kidney sparing alternative to calcineurin inhibitors (CNI).

AREAS COVERED

Herein we review mTOR inhibitors safety profile for adult organ transplantation, ranging from acute side effects, such as lymphoceles, delayed wound healing, or cytopenias, to long-term ones which increase morbidity and mortality, such as cancer risk and metabolic profile. Infection, proteinuria, and cutaneous safety profiles are also addressed.

EXPERT OPINION

In the authors' opinion, mTOR inhibitors are a safe alternative to standard immunosuppression therapy with CNI and mycophenolate/azathioprine. Mild adverse events can be easily managed with an increased awareness and close monitoring of trough levels. Most serious side effects are dose- and organ-dependent. In kidney and heart transplantation mTOR inhibitors may be safely used as either low-dose de novo or through early-conversion. In the liver, conversion 4 weeks post-transplantation may reduce long-term chronic kidney disease secondary to calcineurin nephrotoxicity, without increasing hepatic artery/portal vein thrombosis.

The Critically Ill Kidney Transplant Recipient: A Narrative Review

Kidney transplantation is the most common solid organ transplantation performed worldwide. Up to 6% of kidney transplant recipients experience a life-threatening complication that requires ICU admission, chiefly in the late posttransplantation period (≥ 6 months). Acute respiratory failure and septic shock are the main reasons for ICU admission. Cardiac pulmonary edema, bacterial pneumonia, acute graft pyelonephritis, and bloodstream infections account for the vast majority of diagnoses in the ICU. Pneumocystis jirovecii pneumonia is the most common opportunistic infection, and one-half of the patients so infected require mechanical ventilation. The incidence of cytomegalovirus visceral infections in the era of preemptive therapy has dramatically decreased. Drug-related neutropenia, sirolimus-related pneumonitis, and posterior reversible encephalopathy syndrome are among the most common immunosuppression-associated toxic effects. Importantly, the impact of critical illness on graft function is worrisome. Throughout the ICU stay, acute kidney injury is common, and about 40% of the recipients require renal replacement therapy. One-half of the patients are discharged alive and free from dialysis. Hospital mortality can reach 30% and correlates with acute illness severity and reason for ICU admission. Transplant characteristics are not predictors of short-term survival. Graft survival depends on pre-ICU graft function, disease severity, and renal toxicity of ICU investigations and treatments.

The inferior impact of antibody-mediated rejection on the clinical outcome of kidney allografts that develop de novo thrombotic microangiopathy

BACKGROUND

Antibody-mediated rejection (AMR) can induce and develop thrombotic microangiopathy (TMA) in renal allografts. A definitive AMR (dAMR) co-presents three diagnostic features. A suspicious AMR (sAMR) is designated when one of the three features is missing.

METHODS

Thirty-two TMA cases overlapping with AMR (AMR+ TMA) were studied, which involved 14 cases of sAMR+ TMA and 18 cases of dAMR+ TMA. Thirty TMA cases free of AMR features (AMR- TMA) were enrolled as control group.

RESULTS

The ratio of complete response to treatment was similar between AMR- TMA and AMR+ TMA group (23.3% vs. 12.5%, p = 0.33), or between sAMR+ TMA and dAMR+ TMA group (14.3% vs. 11.1%, p = 0.79). At eight yr post-transplantation, the death-censored graft survival (DCGS) rate of AMR- TMA group was 62.8%, which was significantly higher than 28.0% of AMR+ TMA group (p = 0.01), but similar between sAMR+ TMA and dAMR+ TMA group (30.0% vs. 26.7%, p = 0.92). Overall, the intimal arteritis and the broad HLA (Human leukocyte antigens) mismatches were closely associated with over time renal allograft failure.

CONCLUSION

The AMR+ TMA has inferior long-term graft survival, but grafts with sAMR+ TMA or dAMR+ TMA have similar characteristics and clinical courses.

Characteristics and Outcomes of Renal Transplant Recipients with Hemolytic Uremic Syndrome in the United States

BACKGROUND

Hemolytic uremic syndrome (HUS) accounts for <1% of renal transplants in the US. There are limited data on the characteristics and outcomes of HUS in pediatric and adult kidney transplant recipients in the US.

METHODS

This study included all renal transplant recipients identified with HUS (N=1,233) as a cause of end-stage renal disease between 1987 and 2013 using the UNOS/OPTN database. The cohort was divided into two age groups: pediatric (N=447) and adult (N=786). Main outcomes were acute rejection rate at one-year, allograft and patient survival, and recurrence of HUS post-transplant. Both age groups were then compared with a propensity score (1:2 ratio) matched control group with an alternative primary kidney disease (non-HUS cohort: pediatric [N= 829] and adult [N=1,547]).

RESULTS

In pediatric cohort, when compared to the PS matched controls, acute rejection, death censored allograft and patient survival was similar in the HUS group. However, in the adult cohort, the graft and patient survivals were significantly worse in the HUS group. HUS was associated with allograft loss (HR=1.40, 95%CI 1.14-1.71) in adult recipients. Patients with HUS recurrence had significantly lower allograft and patient survival rates compared to the non-recurrent group in both age groups. Acute rejection was one of the major predictor of HUS recurrence in adults (OR=2.64, 95%CI 1.25-5.60). Calcineurin inhibitors (CNI) were not associated HUS recurrence in both age groups.

CONCLUSION

Pediatric HUS-patients, unlike adult recipients, have similar outcomes compared to the PS matched controls. Recurrence of HUS is associated with poor allograft and patient survival in pediatric and adult patients. Use of CNIs seem to be safe as a part of maintenance immunosuppression post-transplantation. A comprehensive national registry is urgently needed.

Everolimus, cyclosporine, and thrombotic microangiopathy: clinical role and preventive tools in renal transplantation

INTRODUCTION

Thrombotic microangiopathy (TMA) is characterized by endothelial cell injury and formation of fibrin thrombi within capillary and arterioles. In renal allograft recipients, TMA mainly presents as hemolytic uremic syndrome. Its occurrence is rare, and diagnosis requires a high degree of suspicion. Drug toxicity, in particular from calcineurin inhibitors (CNIs) and mTOR inhibitors (mTORi), is the most common cause posttransplant and has recently been emphasized in the setting of lung transplantation.

OBJECTIVE

The goal of this study was to investigate the role of mTORi as an added risk factor in the development of TMA to propose strategies for modulation of immunosuppressive (IS) therapy.

PATIENTS AND METHODS

From a database of 496 renal graft recipients, we analyzed 350 renal graft biopsy specimens gathered at our center from 1998 to 2012. In patients undergoing combined therapy with mTORi and CNI, we compared drugs levels in TMA-affected and TMA-free groups, using mTORi and CNI TLC and the summation of [everolimus TLC+(cyclosporine C2/100)] (Σ) as a surrogate marker of combined exposition to 2 drugs. Receiver-operating characteristic analysis of association of EVL TLC+(C2/100) was performed for patients exposed to mTORi.

RESULTS

Histologic features of TMA were found in 36 patients (prevalence of 7.3%). The caseload was divided into 2 groups: not drug-related TMA (n=19) and drug-related TMA (n=17). Despite the prevalence of TMA in patients exposed to mTORi being greater (8 of 153; prevalence, 5.3%) compared with therapies without mTORi (9 of 324; prevalence, 2.8%), statistical difference was not reached. Patients treated with mTORi who developed de novo drug-related TMA had higher blood levels of IS drugs compared with those who did not develop TMA. Receiver-operating characteristic analysis found a significant threshold of 12.5 ng/mL (area under the curve, 0.803; P=.006).

CONCLUSIONS

Results confirm the pivotal role of IS drugs in the onset of de novo TMA. On the basis of literature, we could speculate a sequence of endothelial damage by CNI, on which everolimus fits hindering the repair of endothelial injury. Therefore, high blood levels of CNI and mTORi seem to predispose patients to posttransplant TMA. Combined monitoring of these 2 drugs might be used to prevent the complication. Σ [everolimus TLC + (cyclosporine C2/100)]>12.5 ng/mL should be avoided as a surrogate risk factor for adverse effects.

Cytomegalovirus-induced thrombotic microangiopathy after renal transplant successfully treated with eculizumab: case report and review of the literature

De novo thrombotic microangiopathy (TMA) after renal transplant is rare. Cytomegalovirus (CMV)-related post-transplant TMA has only been reported in 6 cases. We report an unusual case of a 75-year-old woman who developed de novo TMA in association with CMV viremia. The recurrence of TMA with CMV viremia, the resolution with treatment for CMV, and the lack of correlation with a calcineurin inhibitor (CNI) in our case support CMV as the cause of the TMA. What is unique is that the use of eculizumab without plasmapheresis led to prompt improvement in renal function. After a failure to identify a genetic cause for TMA and the clear association with CMV, eculizumab was discontinued. This case provides insight into the pathogenesis and novel treatment of de novo TMA, highlights the beneficial effects of complement inhibitors in this disease, and shows that they can be safely discontinued once the inciting etiology is addressed.

Differing tales of two patients after receiving a kidney transplant from a donor with disseminated intravascular coagulation

In order to decrease the time on the deceased donor kidney wait list and to have more organs available, criteria for acceptable organs for transplant could be made less stringent. There are reports of successful recipient outcomes using kidney donors presenting with disseminated intravascular coagulation (DIC). We report a unique circumstance where two patients received kidneys from the same deceased donor who had DIC; one patient developed thrombotic microangiopathy (TMA) while the other did not. This difference in outcome may indicate that both donor and recipient factors contribute to the development of posttransplant TMA.

An analysis of transplant glomerulopathy and thrombotic microangiopathy in kidney transplant biopsies

Glomerular diseases of the transplanted kidney are the most important cause of poor long- term outcome. The estimation of the magnitude of this problem and an elucidation of pathogenic mechanism is essential for improvement of graft survival. This study from the Indian subcontinent aims (i) to determine the incidence of transplant glomerulopathy (TG) and thrombotic microangiopathy (TMA) in a large cohort of indicated renal transplant biopsies, (ii) to evaluate the histological and ultrastructural features of TG and TMA, and (iii) to assess the relationship between the two glomerular lesions. Of a total of 1792 indication renal transplant biopsies received over 5 years (2006-2010), 266 biopsies (of 249 patients) had significant glomerular pathology and were further analyzed along with immunofluorescence, electron microscopy (EM), and C4d immunohistochemistry. TG is the most common glomerular lesion followed by TMA seen in 5.97% and 5.08% of allograft biopsies, respectively, which constitutes 40.23% and 34.2% of biopsies with significant glomerular lesions. Pathologic antibody-mediated rejection (AMR) is associated with both TG and TMA in 71% and 46.5%, respectively. A coexistent TG was found in 18.4% of biopsies with TMA. Endothelial swelling with subendothelial widening, a feature of TMA, is also seen in early TG by EM. Our findings support the concept that TG evolves from a smoldering TMA of various causes.

De novo glomerular diseases after renal transplantation

Glomerular diseases developing in the kidney allograft are more often recurrences of the original disease affecting the native kidneys. However, in an undefined number of cases de novo, glomerular diseases unrelated to the original disease in the native kidneys can develop in the transplanted kidney. The clinical presentation and histologic features of de novo diseases are often similar to those features observed in patients with primary or secondary GN in the native kidneys. However, in transplanted kidneys, the glomerular, vascular, and tubulointerstitial changes are often intertwined with structural abnormalities already present at the time of transplant or caused by antibody- or cell-mediated allograft rejection, immunosuppressive drugs, or superimposed infection (most often of a viral nature). The pathophysiology of de novo glomerular diseases is quite variable. In rare cases of de novo minimal change disease, circulating factors increasing the glomerular permeability likely participate. Maladaptive hemodynamic changes and tissue fibrosis caused by calcineurin inhibitors or other factors may be involved in the pathogenesis of de novo FSGS. The exposure of cryptic podocyte antigens may favor the development of de novo membranous nephropathy. Many cases of de novo membranoproliferative GN are related to hepatitis C virus infection. Patients with Alport syndrome lacking antigenic epitopes in their glomerular basement membrane may develop antibodies against these glomerular basement membrane antigens expressed in the transplanted kidney. Infection may cause acute GN to have a heterogeneous clinical presentation and outcome. De novo pauci-immune GN in renal transplant is rare. Preexisting or acquired intolerance to glucose may, in the long term, cause diabetic nephropathy. The prognosis of de novo diseases depends on the type of GN, the severity of lesions caused by the alloimmune response, or the efficacy of immunosuppressive therapy. In most cases, the management of de novo glomerular diseases is empirical or elusive.

Acute kidney injury in solid organ transplant recipients

Delayed and slow graft function (DGF/SGF) in de novo kidney transplantation endanger outcomes of graft and patient, while predisposing the patient to acute rejection and lesser graft function. Causes and work-up of DGF/SGF are described in the present paper. Also, the epidemiology and pathophysiology of chronic renal failure both in kidney graft recipients and in recipients of other solid organs is discussed, especially in relation to calcineurin inhibitor (CNI) immunosuppression. An acute kidney injury event will have a greater and faster impact on impaired renal reserve in case of chronic renal failure. Major causes of acute kidney injury (AKI) of the native kidneys of solid organ recipients and of the transplanted kidney are: severe infections, acute toxic kidney injury caused by CNI treatment concomitant CYP450 3A4 inhibiting medication, toxic and infectious events inducing haemolytic uraemic syndrome, toxic rhabdomyolysis, acute interstitial nephritis, rapid IV immunoglobulin infusion and exposure to other well-known nephrotoxins, such as NSAIDs, amphotericin and aminoglycosides.

Blood disorders after kidney transplantation

Post transplant anemia (PTA) is a common issue in kidney transplant recipients. Most importantly it is associated with an impaired allograft function. Other important factors associated with PTA are immunosuppressive drugs (MPA, AZA and SRL), iron deficiency, infections (Parvo B19), older donor age, rejection episodes, an increased inflammatory state, and erythropoietin hyporesponsiveness. As there are no adequately powered RCTs in the kidney transplant population on anemia treatment with ESA, we have to rely on what we know from the large RCTs in the CKD population. The recently published KDIGO guidelines do not recommend treatment with ESA if Hb is >10 g/dl. Repletion of iron stores is emphasized. Post transplant leukopenia (PTL) and thrombocytopenia (PTT) are frequent complications especially in the first six months after kidney transplantation. Myelosuppression caused by immunosuppressive agents (MPA, AZA, SRL, rATG), antimicrobial drugs (VGCV), and CMV infection is the predominant cause. There are no widely accepted guidelines on treatment strategies, but most often dose reduction or discontinuation of causative medication is done. Most clinicians tend to decrease MPA dose, but this is eventually associated with an increase in acute rejection episodes. VGCV dose reduction (preemptive treatment instead of CMV prophylaxis) may be a successful strategy. In severe cases G-CSF treatment is an important management option and seems to be safe.

Glomerular mRNA expression of prothrombotic and antithrombotic factors in renal transplants with thrombotic microangiopathy

BACKGROUND

Thrombotic microangiopathy (TMA) in renal transplants (rTx-TMA) is a serious complication and is usually either recurrent TMA (RecTMA) due to humoral rejection (HR-TMA) or due to calcineurin inhibitor toxicity (CNI-TMA). Although the triggers are known, our knowledge about the thrombogenic transcriptome changes in the microvessels is rudimentary.

METHODS

We examined the expression of several prothrombotic and antithrombotic genes in 25 biopsies with rTx-TMA (6 RecTMA, 9 HR-TMA, and 10 CNI-TMA) and 8 controls. RNA from microdissected glomeruli of paraffin-embedded tissue was isolated and mRNA transcripts were quantified with real-time polymerase chain reaction after preamplification. Results were correlated with clinicopathologic parameters.

RESULTS

Glomerular mRNA expression of KLF2, KLF4, and tPA was lower and that of PAI-1 was higher in rTx-TMA than in the controls. Glomerular mRNA expression of KLF2 and KLF4 correlated with that of tPA and inversely with that of PAI-1 in rTx-TMA. The mRNA expression of complement regulators CD46 and CD59 were higher in rTx-TMA than in the controls. Only in HR-TMA were glomerular ADAMTS13 and CD55 down-regulated.

CONCLUSIONS

The glomerular capillary bed seems to contribute to all subtypes of rTx-TMA by down-regulation of the endothelial transcription factors KLF2 and KLF4, indicating dedifferentiation with subsequent up-regulation of PAI-1 and down-regulation of tPA, resulting in inhibition of local fibrinolysis. Decreased glomerular expression of ADAMTS13 and CD55 could be an additional pathway toward microthrombosis exclusively in HR-TMA.

Eculizumab treatment of acute antibody-mediated rejection in renal transplantation: case reports

The occurrence of acute antibody-mediated rejection (AMR), especially in more severe cases, continues to be associated with a poor prognosis for implant survival. Here, we have reported the results of treatment of two patients who developed AMR associated with thrombotic microangiopathy immediately after transplantation. We used a single dose of eculizumab at an early stage jointly with conventional modalities of steroid boluses, plasmapheresis, intravenous immunoglobulin, and rituximab. In both cases, the clinical course was favorable. Eculizumab, a monoclonal antibody with a high affinity for complement protein C5, prevents generation of the final membrane attack complex, blocking this cascade. To date, there are a few reports of the usefulness of eculizumab in AMR. Eculizumab can help to stop endothelial damage, especially in severe cases that show a risk of progression to cortical necrosis, by providing a therapeutic window until the other modalities begin to control the immune response. In our experience, the use of eculizumab can be beneficial in the treatment of AMR.

De novo thrombotic microangiopathy after kidney transplantation: clinical features, treatment, and long-term patient and graft survival

INTRODUCTION

Posttransplant thrombotic microangiopathy (TMA)/hemolytic uremic syndrome (HUS) can occur as a recurrent or de novo disease.

METHODS

A retrospective single-center observational study was applied in order to examine the incidence and outcomes of de novo TMA/HUS among transplantations performed between 2000 and 2010. Recurrent HUS or antibody-mediated rejections were excluded.

RESULTS

Seventeen (1.1%) among 1549 kidney transplant recipients fulfilled criteria for de novo TMA. The mean follow-up was 572 days (range, 69-1769). Maintenance immunosuppression was prednisone, tacrolimus (TAC), and mycophenolic acid in 14 (82%) patients. Mean age at onset was 40 ± 15 years, and serum creatinine was 6.1 ± 4.1 mg/dL. TMA occurred at a median of 25 days (range, 1-1755) after transplantation. Nine (53%) patients developed TMA within 1 month of transplantation and only 12% after 1 year. Clinical features were anemia (hemoglobin < 10 g/dL) in 9 (53%) patients, thrombocytopenia in 7 (41%), and increased lactate dehydrogenase in 12 (70%). Decreased haptoglobin was observed in 64% and schistocytes in 35%. Calcineurin inhibitor (CNI) withdrawal or reduction was the first step in the management of 10/15 (66%) patients, and 6 (35%) received fresh frozen plasma (FFP) and/or plasmapheresis. TAC was successfully reintroduced in six patients after a median of 17 days. Eight (47%) patients needed dialytic support after TMA diagnosis and 75% remained on dialysis. At 4 years of follow-up, death-censored graft survival was worse for TMA group (43.0% versus 85.6%, log-rank = 0.001; hazard ratio = 3.74) and there was no difference in patient survival (53.1% versus 82.2%, log-rank = 0.24).

CONCLUSION

De novo TMA after kidney transplantation is a rare but severe condition with poor graft outcomes. This syndrome may not be fully manifested, and clinical suspicion is essential for early diagnosis and treatment, based mainly in CNI withdrawal and FFP infusions and/or plasmapheresis.

Tacrolimus associated localized thrombotic microangiopathy developing in early stage after renal transplantation

Calcineurin inhibitor induced thrombotic microangiopathy is a rare but well recognized complication of a renal transplantation that occurs in 1% of the patients who are on tacrolimus immunosuppression. Among the other aetiological factors of the "de-novo" Thrombotic Microangiopathy (TMA), the condition especially has to be differentiated from an antibody mediated rejection, as both have different pathogenesis, therapeutic connotations and outcomes.We report a case of a middle aged female renal transplant recipient treated with tacrolimus, who developed localised thrombotic microangiopathy in the early post transplantation period. Despite the normal trough levels of tacrolimus, a diagnosis of "Tacrolimus induced TMA" was rendered after excluding other causes of the "de-novo" TMA, which included an antibody mediated rejection, a meticulous clinico-pathological correlation and serological studies. The treatment included the substitution of tacrolimus by rapamycin, with the subsequent normalization of the renal function.

Antibody mediated rejection associated with complement factor h-related protein 3/1 deficiency successfully treated with eculizumab

Antibody mediated rejection (AMR) activates the classical complement pathway and can be detrimental to graft survival. AMR can be accompanied by thrombotic microangiopathy (TMA). Eculizumab, a monoclonal C5 antibody prevents induction of the terminal complement cascade (TCC) and has recently emerged as a therapeutic option for AMR. We present a highly sensitized 13-year-old female with end-stage kidney disease secondary to spina bifida-associated reflux nephropathy, who developed severe steroid-, ATG- and plasmapheresis-resistant AMR with TMA 1 week post second kidney transplant despite previous desensitization therapy with immunoglobulin infusions. Eculizumab rescue therapy resulted in a dramatic improvement in biochemical (C3; creatinine) and hematological (platelets) parameters within 6 days. The patient was proven to be deficient in complement Factor H-related protein 3/1 (CFHR3/1), a plasma protein that regulates the complement cascade at the level of C5 conversion and has been involved in the pathogenesis of atypical hemolytic uremic syndrome caused by CFH autoantibodies (DEAP-HUS). CFHR1 deficiency may have worsened the severe clinical progression of AMR and possibly contributed to the development of donor-specific antibodies. Thus, screening for CFHR3/1 deficiency should be considered in patients with severe AMR associated with TMA.

Thrombotic microangiopathy after living-donor liver transplantation

Thrombotic microangiopathy (TMA) is an infrequent but severe life-threatening disorder in solid organ transplant recipients. Few studies of TMA in living donor liver transplant (LDLT) recipients, however, have been reported. We investigated the clinical characteristics and prognostic factors of TMA after LDLT. Among 393 adult LDLT recipients, 30 patients (7.6%) were identified to have TMA. The 1-, 3- and 5-year survival rates of these patients were lower (60.6%, 52.5% and 47.7%, respectively) than those of patients without TMA (93.0%, 89.0% and 87.3%, respectively). Multivariate analysis confirmed that reduced administration of fresh frozen plasma and sensitization against HLA are closely related with TMA (odds ratio [OR]: 2.6 and 16.1, respectively). However, a review of the cases revealed that individual responses to treatment varied considerably and the main etiologies were difficult to determine. A comparison of the clinical factors suggested that late onset (>30 days), poor response to treatment and delayed diagnosis and/or treatment are associated with a poor outcome. Because the prevention of TMA in LDLT patients is difficult, early diagnosis and initiation of intensive therapies may be crucial to improve the prognosis.