Calcineurin inhibitor-free immunosuppression in renal allograft recipients with thrombotic microangiopathy/hemolytic uremic syndrome

Recurrent disease after pediatric renal transplantation

BACKGROUND

Recurrent disease after kidney transplant remains an important cause of allograft failure, accounting for 7-8% of graft loss and ranking as the fifth most common cause of allograft loss in the pediatric population. Although the pathophysiology of many recurrent diseases is incompletely understood, recent advances in basic science and therapeutics are improving outcomes and changing the course of several of these conditions.

METHODS

Review of the literature.

RESULTS

We discuss the diagnosis and management of recurrent disease.

CONCLUSION

We highlight new insights into the pathophysiology and treatment of post-transplant primary hyperoxaluria, focal segmental glomerulosclerosis, immune complex glomerulonephritis, C3 glomerulopathy, lupus nephritis, atypical hemolytic uremic syndrome, and IgA nephropathy.

Unveiling the Incidence and Graft Survival Rate in Kidney Transplant Recipients With De Novo Thrombotic Microangiopathy: A Systematic Review and Meta-Analysis

De novo thrombotic microangiopathy (TMA) is a rare and challenging condition in kidney transplant recipients, with limited research on its incidence and impact on graft survival. This study conducted a systematic review and meta-analysis of 28 cohorts/single-arm studies and 46 case series/reports from database inception to June 2022. In meta-analysis, among 14,410 kidney allograft recipients, de novo TMA occurred in 3.20% [95% confidence interval (CI): 1.93-4.77], with systemic and renal-limited TMA rates of 1.38% (95% CI: 06.5-2.39) and 2.80% (95% CI: 1.27-4.91), respectively. The overall graft loss rate of de novo TMA was 33.79% (95% CI: 26.14-41.88) in meta-analysis. This study provides valuable insights into the incidence and graft outcomes of de novo TMA in kidney transplant recipients.

Predicting the risk of acute kidney injury after hematopoietic stem cell transplantation: development of a new predictive nomogram

The purpose was to predict the risk of acute kidney injury (AKI) within 100 days after hematopoietic stem cell transplantation (HSCT) in patients with hematologic disease by using a new predictive nomogram. Collect clinical data of patients with hematologic disease undergoing HSCT in our hospital from August 2012 to March 2018. Parameters with non-zero coefficients were selected by the Least Absolute Selection Operator (LASSO). Then these parameters were selected to build a new predictive nomogram model. Receiver operating characteristic (ROC) curve, calibration curve, C-index, and decision curve analysis (DCA) were used for the validation of the evaluation model. Finally, the nomogram was further evaluated by internal verification. According to 2012 Kidney Disease Improving Global Guidelines (KDIGO) diagnostic criteria, among 144 patients, the occurrence of AKI within 100 days after HSCT The rate was 29.2% (42/144). The C-index of the nomogram was 0.842. The C-value calculated by the internal verification was 0.809. The AUC was 0.842, and The DCA range of the predicted nomogram was from 0.01 to 0.71. This article established a high-precision nomogram for the first time for predicting the risk of AKI within 100 days after HSCT in patients with hematologic diseases. The nomogram had good clinical validity and reliability. For clinicians, it was very important to prevent AKI after HSCT.

Complement Mediated Endothelial Damage in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMA) constitute a group of different disorders that have a common underlying mechanism: the endothelial damage. These disorders may exhibit different mechanisms of endothelial injury depending on the pathological trigger. However, over the last decades, the potential role of the complement system (CS) has gained prominence in their pathogenesis. This is partly due to the great efficacy of complement-inhibitors in atypical hemolytic syndrome (aHUS), a TMA form where the primary defect is an alternative complement pathway dysregulation over endothelial cells (genetic and/or adquired). Complement involvement has also been demonstrated in other forms of TMA, such as thrombotic thrombocytopenic purpura (TTP) and in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS), as well as in secondary TMAs, in which complement activation occurs in the context of other diseases. However, at present, there is scarce evidence about the efficacy of complement-targeted therapies in these entities. The relationship between complement dysregulation and endothelial damage as the main causes of TMA will be reviewed here. Moreover, the different clinical trials evaluating the use of complement-inhibitors for the treatment of patients suffering from different TMA-associated disorders are summarized, as a clear example of the entry into a new era of personalized medicine in its management.

De Novo and Recurrent Thrombotic Microangiopathy After Renal Transplantation: Current Concepts in Management

Thrombotic microangiopathy is a well-recognized complication of kidney transplantation that leads frequently to allograft failure. This serious outcome can greatly depend on the underlying etiology and on the timing of therapeutic interventions. Thrombotic microangiopathy syndrome may occur with no previous history of thrombotic microangiopathy (that is, de novo thrombotic microangiopathy), mostly due to medica tions or infections. More frequently, it may recur after kidney transplant in patients with endstage renal failure due to atypical hemolytic uremic syndrome. However, for patients with Shiga-toxininduced hemolytic uremic syndrome, particularly pediatric patients, there is a favorable prognosis. A fundamental tool for management of this disease is genetic screening for abnormal mutations; this can recognize the suggested approach of therapy and may determine the outcome of the disease to a large extent. Although patients with complement factor H and I mutations have worse prognosis, other patients with membrane cofactor protein mutations, for example, have a more favorable prognosis. Accordingly, the plan of therapy can be tailored with a better chance of cure. Unfortunately, the successful use of the biological agent eculizumab, an anti-C5 agent, in some of these syndromes is largely impeded by its high cost, which is linked to its use as a life-long therapy. However, newly suggested therapeutic options may ameliorate this drawback.

Acute Kidney Injury in the Modern Era of Allogeneic Hematopoietic Stem Cell Transplantation

Background and objectives Acute kidney injury (AKI) is a major complication of allogeneic hematopoietic stem cell transplantation, increasing risk of non-relapse mortality. AKI etiology is often ambiguous due to heterogeneity of conditioning/graft-versus-host disease (GVHD) regimens. To date, GVHD and calcineurin inhibitor effects on AKI are not well defined. We aimed to describe AKI and assess pre/post-hematopoietic transplant risk factors in a large recent cohort. Design, setting, participants, and measurements We performed a single-center retrospective study of 616 allogeneic hematopoietic cell transplant recipients from 2014-2017. We defined AKI and CKD based on KDIGO criteria and estimated GFR using CKD-EPI equation. We assessed AKI pre/post-hematopoietic transplant risk factors using cause-specific Cox regression and association of AKI with CKD outcomes using Chi-squared test. AKI was treated as a time-dependent variable in relation to non-relapse mortality. Results Incidence of AKI by day-100 was 64%. Exposure to tacrolimus and other nephrotoxins conferred a higher risk of AKI, but tacrolimus levels were not associated with severity. Reduced intensity conditioning carried higher AKI risk compared to myeloablative conditioning. Most stage 3 AKIs were due to ischemic acute tubular necrosis and CNI nephrotoxicity. Kidney replacement therapy was initiated in 21/616 (3%) of whom 9/21 (43%) recovered and 5/21 (24%) survived to hospital discharge. T-cell depleted transplants, higher baseline albumin, and non-Hispanic ethnicity were associated with lower risk of AKI. CKD developed in 21% (73/345) of patients after 12 months. Non-relapse mortality was higher in those with AKI (HR 2.77, 95% CI: 1.8-4.27). Conclusions AKI post-hematopoietic cell transplant remains a major concern. Risk of AKI was higher with exposure to CNIs. T cell depleted hematopoietic cell transplants and higher albumin had lower risk of AKI. Forty-three percent of patients requiring KRT recovered kidney function. Prospective studies are needed to further assess modification of these risk factors.

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.

Eculizumab in atypical hemolytic uremic syndrome: strategies toward restrictive use

With the introduction of the complement C5-inhibitor eculizumab, a new era was entered for patients with atypical hemolytic uremic syndrome (aHUS). Eculizumab therapy very effectively reversed thrombotic microangiopathy and reduced mortality and morbidity. Initial guidelines suggested lifelong treatment and recommended prophylactic use of eculizumab in aHUS patients receiving a kidney transplant. However, there is little evidence to support lifelong therapy or prophylactic treatment in kidney transplant recipients. Worldwide, there is an ongoing debate regarding the optimal dose and duration of treatment, particularly in view of the high costs and potential side effects of eculizumab. An increasing but still limited number of case reports and small cohort studies suggest that a restrictive treatment regimen is feasible. We review the current literature and focus on the safety and efficacy of restrictive use of eculizumab. Our current treatment protocol is based on restrictive use of eculizumab. Prospective monitoring will provide more definite proof of the feasibility of such restrictive treatment.

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.

Frequency of the Original Kidney Disease and Its Effect on the Outcome of Kidney Transplant in the Urology-Nephrology Center Mansoura University

OBJECTIVES

Renal allograft function and graft survival depends on many factors, including the source of the graft, immunologic matching between donor and recipient, incidence of acute rejection, and recurrence of the original kidney disease. This work aimed to evaluate the effects of the original kidney disease on patient and graft survival.

MATERIALS AND METHODS

This was a retrospective, single-center study that included 2189 kidney transplant recipients who were transplanted at The Urology and Nephrology Centre, Mansoura University, between 1976 and 2010. Of 2189 recipients, 1350 patients with unknown original kidney disease were excluded, with the remaining 839 patients divided into 4 groups according to their original kidney disease.

RESULTS

We found pretransplant dialysis and blood transfusion to be statistically significant among the 4 groups. Regarding induction immunosuppressive therapy, a statistical significance was found between the 4 groups regarding the presence and type of induction therapy, with no statistical significance regarding the type of maintenance immunosuppression. There was no statistical significance between the 4 groups regarding the incidence of acute and chronic rejection. We also found recurrence of original kidney disease to be statistically significant in the 4 groups, particularly in the group that included patients with glomerular disease, where the highest rate of recurrence was reported in patients with focal segmental glomerulosclerosis and membranoproliferative glomerulonephritis, and patient and graft survival was also statistically significant.

CONCLUSIONS

The original kidney disease has an effect on renal allograft function and graft and patient survival.

Favorable four-yr outcome after renal transplantation in a patient with complement factor H antibody and CFHR1/CFHR3 gene mutation-associated HUS

aHUS is a clinical challenge for successful renal transplantation.

CASE REPORT

A 14-yr-old girl lost her kidneys at the age of 7, due to CFH antibodies and CFH-related protein (CFHR1/CFHR3) homozygous deletion-associated aHUS. CFH, CFI, and MCP gene mutations were excluded. The patient was a candidate for renal transplantation despite persistent presence of CFH antibodies (up to 539 AU/mL). Treatment with MMF, IVIG, and repeated PF (n = 8) was introduced while being placed on urgent waiting list. Three years after aHUS onset, the patient underwent the deceased donor renal transplantation "under cover" of PF, as PF was performed directly prior to surgery and, then, PFs were repeated up to overall 14 sessions. Quadruple immunosuppression (basiliximab + tacrolimus + MMF + prednisolone) was used. Moderate symptoms of aHUS (hemolysis, low platelets, and low C3) were present within first seven days post-transplant and then normalized with PF therapy. The patient remained stable during four yr of further follow-up after transplantation.

CONCLUSION

Specific pre- and post-transplant management allowed successful renal transplantation in a CFH antibody-positive patient.

Novel aspects of atypical haemolytic uraemic syndrome and the role of eculizumab

The haemolytic uraemic syndrome (HUS) is part of a spectrum of thrombotic microangiopathies. The most common etiologies of HUS are the ones seen in childhood caused by an infection of Shiga toxin-producing Escherichia coli, HUS caused by an infection with Streptococcus pneumoniae and HUS due to abnormalities in the alternative pathway of the complement system. In the past decade, enormous progress has been made in understanding the pathogenesis in the latter group of patients. The analysis of genes that encode for complement regulatory proteins and the development of assays for measuring the activity of ADAMTS13 and the detection of antibodies against factor H contributed significantly to the diagnostic tools in patients with HUS. These assays have made it possible to clearly differentiate between thrombotic thrombocytopenic purpura and various forms of HUS. With the introduction of eculizumab, a monoclonal anti-C5 inhibitor, in the clinical arena as effective treatment of most complement-mediated forms of HUS, a new era of treatment in HUS has begun. We review the recent advances in HUS, with the focus on treatment. We discuss unsolved questions, which should be addressed in future studies.

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.

Managing transplant rejection in the elderly: the benefits of less aggressive immunosuppressive regimens

Organ transplantation is increasingly common in the older population, particularly among end-stage renal disease patients. The outcomes of transplantation are often inferior in older people compared with younger recipients, partly because of the side effects of immunosuppressive medication used after organ transplantation. In this paper, we explore treatment considerations for older transplant patients. The current commonly used immunosuppressive protocols have not been validated sufficiently in older organ recipients. The primary objective for the management of transplant recipients of all ages is to prevent rejection without increasing the risk of infection or other long-term complications. To avoid serious side effects related to immunosuppressive treatment, the clinician should consider modifying and tailoring the long-term regimen for individual patients. Modifications for older recipients include reduction in the dosage or avoidance of calcineurin inhibitors, with or without the introduction of a mammalian target of rapamycin inhibitor and discontinuing the use of corticosteroids. Such modifications must consider the individual risks and needs of each recipient. Treatment of an acute rejection episode should follow the same protocol as for younger recipients, but special attention is needed to ensure reduction in the total immunosuppressive load. One way to achieve this is to avoid anti-thymocyte globulin (ATG) induction and to use on-demand ATG treatment of rejection on the basis of the patient's CD3 T cell count.

Case series: hemolytic uremic syndrome--another cause of transplant dysfunction

BACKGROUND

Renal transplantation is the optimal treatment for suitable patients with end-stage renal disease (ESRD). However, acute graft dysfunction occurs in 5%-35% of patients. This is commonly due to acute rejection, drug toxicity, ureteric obstruction, or infection. Atypical hemolytic uremic syndrome (aHUS), either recurrent or de novo, is uncommon after transplantation.

CASES

We highlight three cases of acute transplant dysfunction in which transplant biopsy revealed HUS without associated clinical or hematologic clues to the etiology. Two cases had recurrent HUS and 1 had de novo HUS secondary to tacrolimus therapy. Screenings for ADAMTS-13 and gene mutations of complement regulatory proteins were negative. Thrombocytopenia and red blood cell fragments on blood film appeared some days later.

TREATMENT

Treatment comprised a combination of plasma exchange with fresh-frozen plasma and switching immunosuppressive therapy, which led to the recovery of the above hematologic features but salvaged graft function in only 1 case.

CONCLUSIONS

Classical hematologic findings of HUS appeared late in these cases. HUS should be considered in cases of allograft dysfunction where there is no obvious cause, and biopsy should be performed. This enables early initiation of therapy to gain rapid recovery of hematologic parameters and potentially of transplant function.

Use of belatacept as alternative immunosuppression in three renal transplant patients with de novo drug-induced thrombotic microangiopathy

Thrombotic microangiopathy (TMA), a severe complication of renal transplantation, is a pathological process involving microvascular occlusion, thrombocytopenia, and microangiopathic hemolytic anemia. It generally appears within the first weeks after transplantation, when immunosuppressive drugs are used at high doses. De novo TMA may also be drug-induced when calcineurin inhibitors or proliferation signal inhibitors are used. We report three cases of de novo drug-induced TMA in renal transplant patients who were managed by replacing calcineurin inhibitors or proliferation signal inhibitors with belatacept, a primary maintenance immunosuppressive drug, which blocks the CD28 costimulation pathway, preventing the activation of T lymphocytes. To identify the cause of TMA, we ruled out HUS, hepatitis C serology, HIV serology, parvovirus B19, cytomegalovirus, anti-HLA antibodies, and prolonged activated partial thromboplastin time. We suspect that the TMA was caused by the calcineurin inhibitors or proliferation signal inhibitors. Belatacept treatment was initiated at a dose of 10 mg/kg on days 1, 5, 14, 28, 60, and 90; maintenance treatment was 5 mg/kg once a month for 1 year. Belatacept, in combination with other agents, prevented graft rejection in three patients.

Update on hemolytic uremic syndrome: Diagnostic and therapeutic recommendations

Hemolytic uremic syndrome (HUS) is a rare disease. In this work the authors review the recent findings on HUS, considering the different etiologic and pathogenetic classifications. New findings in genetics and, in particular, mutations of genes that encode the complement-regulatory proteins have improved our understanding of atypical HUS. Similarly, the complement proteins are clearly involved in all types of thrombotic microangiopathy: typical HUS, atypical HUS and thrombotic thrombocytopenic purpura (TTP). Furthermore, several secondary HUS appear to be related to abnormalities in complement genes in predisposed patients. The authors highlight the therapeutic aspects of this rare disease, examining both “traditional therapy” (including plasma therapy, kidney and kidney-liver transplantation) and “new therapies”. The latter include anti-Shiga-toxin antibodies and anti-C5 monoclonal antibody “eculizumab”. Eculizumab has been recently launched for the treatment of the atypical HUS, but it appears to be effective in the treatment of typical HUS and in TTP. Future therapies are in phases I and II. They include anti-C5 antibodies, which are more purified, less immunogenic and absorbed orally and, anti-C3 antibodies, which are more powerful, but potentially less safe. Additionally, infusions of recombinant complement-regulatory proteins are a potential future therapy.

Complement genes strongly predict recurrence and graft outcome in adult renal transplant recipients with atypical hemolytic and uremic syndrome

Atypical hemolytic and uremic syndrome (aHUS) is a severe disease strongly associated with genetic abnormalities in the complement alternative pathway. In renal posttransplantation, few data are available on recurrence risk and graft outcome according to genetic background in aHUS patients. The aim of this study was to identify risk factors for recurrence and transplant outcome and, in particular, the role of complement gene abnormalities. We retrospectively studied 57 aHUS patients who had received 71 renal transplants. A mutation in complement gene was identified in 39 (68%), in factor H (CFH), factor I (CFI), membrane cofactor-protein (MCP), C3 and factor B (CFB). At 5 years, death-censored graft survival was 51%. Disease recurrence was associated with graft loss (p = 0.001). Mutations in complement genes were associated with higher risk of recurrence (p = 0.009). Patients with CFH or gain of function (C3, CFB) mutations had a highest risk of recurrence. M-TOR inhibitor was associated with significant risk of recurrence (p = 0.043) but not calcineurin inhibitor immunosuppressive treatment (p = 0.29). Preemptive plasmatherapy was associated with a trend to decrease recurrence (p = 0.07). Our study highlights that characterization of complement genetic abnormalities predicts the risk of recurrence-related graft loss and paves the way for future genetically based individualized prophylactic therapeutic strategies.

An evaluation of sirolimus in renal transplantation

INTRODUCTION

Sirolimus is a powerful antiproliferative immunosuppressive drug approved for the prevention of kidney allograft rejection. By its unique mechanism of action, sirolimus provides a multitude of clinical potential and has been used effectively in different drug combinations. Extensive experience has been gained regarding the best timing of its application, side effect profile and potential benefits and limitations compared with other immunosuppressive drugs.

AREAS COVERED

The authors evaluate the recent experience with sirolimus in kidney transplantation. Pivotal randomized controlled trials were used to provide an overview with special attention to pharmacokinetic and dynamic aspects of sirolimus, its current clinical use as well as perspectives for its future role.

EXPERT OPINION

Sirolimus enriches the possibilities of immunosuppressive therapies after renal transplantation. Beneficial effects toward kidney function by allowing CNI sparing, lower incidence of malignancies and less viral infections have been suggested. Sirolimus should be used cautiously in de novo patients for reasons of wound healing. An early conversion to a sirolimus-based CNI-free regimen has shown promising results, whereas late conversion is more challenging. Finally, sirolimus-associated side effects are causing tolerability concerns and frequent discontinuations. Future research should aim to better define the therapeutic window and those patients most likely to benefit.

Eculizumab in acute recurrence of thrombotic microangiopathy after renal transplantation

Renal thrombotic microangiopathy (TMA) is a severe complication of systemic lupus erythematosus (SLE), which is associated with the presence of antiphospholipid (aPL) antibodies. In its most fulminant form, TMA leads to a rapid and irreversible end-stage renal failure. Eculizumab, an anti-C5 monoclonal antibody, is a novel therapy of choice for patients with paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome. Here, we report the case of a 27-year-old woman, known for SLE and end-stage renal disease due to fulminant TMA. Both aPL antibodies and antinucleosome antibodies were positive. The patient underwent a living-related kidney transplantation with immediate production of urine. Although serum creatinine was remaining high, a graft biopsy, performed on day 6, demonstrated a TMA recurrence. Despite a treatment with plasma exchange, the situation got worse and dialysis was started. Eculizumab treatment was subsequently administered and renal function improved rapidly. Three months after transplantation, serum creatinine was at 100 μmol/L, without proteinuria. This case illustrates the benefit of eculizumab therapy in a fulminant recurrence of TMA after kidney transplantation, resistant to classical therapy.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by the triad of mechanical hemolytic anemia, thrombocytopenia and renal impairment. Atypical HUS (aHUS) defines non Shiga-toxin-HUS and even if some authors include secondary aHUS due to Streptococcus pneumoniae or other causes, aHUS designates a primary disease due to a disorder in complement alternative pathway regulation. Atypical HUS represents 5 -10% of HUS in children, but the majority of HUS in adults. The incidence of complement-aHUS is not known precisely. However, more than 1000 aHUS patients investigated for complement abnormalities have been reported. Onset is from the neonatal period to the adult age. Most patients present with hemolytic anemia, thrombocytopenia and renal failure and 20% have extra renal manifestations. Two to 10% die and one third progress to end-stage renal failure at first episode. Half of patients have relapses. Mutations in the genes encoding complement regulatory proteins factor H, membrane cofactor protein (MCP), factor I or thrombomodulin have been demonstrated in 20-30%, 5-15%, 4-10% and 3-5% of patients respectively, and mutations in the genes of C3 convertase proteins, C3 and factor B, in 2-10% and 1-4%. In addition, 6-10% of patients have anti-factor H antibodies. Diagnosis of aHUS relies on 1) No associated disease 2) No criteria for Shigatoxin-HUS (stool culture and PCR for Shiga-toxins; serology for anti-lipopolysaccharides antibodies) 3) No criteria for thrombotic thrombocytopenic purpura (serum ADAMTS 13 activity > 10%). Investigation of the complement system is required (C3, C4, factor H and factor I plasma concentration, MCP expression on leukocytes and anti-factor H antibodies; genetic screening to identify risk factors). The disease is familial in approximately 20% of pedigrees, with an autosomal recessive or dominant mode of transmission. As penetrance of the disease is 50%, genetic counseling is difficult. Plasmatherapy has been first line treatment until presently, without unquestionable demonstration of efficiency. There is a high risk of post-transplant recurrence, except in MCP-HUS. Case reports and two phase II trials show an impressive efficacy of the complement C5 blocker eculizumab, suggesting it will be the next standard of care. Except for patients treated by intensive plasmatherapy or eculizumab, the worst prognosis is in factor H-HUS, as mortality can reach 20% and 50% of survivors do not recover renal function. Half of factor I-HUS progress to end-stage renal failure. Conversely, most patients with MCP-HUS have preserved renal function. Anti-factor H antibodies-HUS has favourable outcome if treated early.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by the triad of mechanical hemolytic anemia, thrombocytopenia and renal impairment. Atypical HUS (aHUS) defines non Shiga-toxin-HUS and even if some authors include secondary aHUS due to Streptococcus pneumoniae or other causes, aHUS designates a primary disease due to a disorder in complement alternative pathway regulation. Atypical HUS represents 5 -10% of HUS in children, but the majority of HUS in adults. The incidence of complement-aHUS is not known precisely. However, more than 1000 aHUS patients investigated for complement abnormalities have been reported. Onset is from the neonatal period to the adult age. Most patients present with hemolytic anemia, thrombocytopenia and renal failure and 20% have extra renal manifestations. Two to 10% die and one third progress to end-stage renal failure at first episode. Half of patients have relapses. Mutations in the genes encoding complement regulatory proteins factor H, membrane cofactor protein (MCP), factor I or thrombomodulin have been demonstrated in 20-30%, 5-15%, 4-10% and 3-5% of patients respectively, and mutations in the genes of C3 convertase proteins, C3 and factor B, in 2-10% and 1-4%. In addition, 6-10% of patients have anti-factor H antibodies. Diagnosis of aHUS relies on 1) No associated disease 2) No criteria for Shigatoxin-HUS (stool culture and PCR for Shiga-toxins; serology for anti-lipopolysaccharides antibodies) 3) No criteria for thrombotic thrombocytopenic purpura (serum ADAMTS 13 activity > 10%). Investigation of the complement system is required (C3, C4, factor H and factor I plasma concentration, MCP expression on leukocytes and anti-factor H antibodies; genetic screening to identify risk factors). The disease is familial in approximately 20% of pedigrees, with an autosomal recessive or dominant mode of transmission. As penetrance of the disease is 50%, genetic counseling is difficult. Plasmatherapy has been first line treatment until presently, without unquestionable demonstration of efficiency. There is a high risk of post-transplant recurrence, except in MCP-HUS. Case reports and two phase II trials show an impressive efficacy of the complement C5 blocker eculizumab, suggesting it will be the next standard of care. Except for patients treated by intensive plasmatherapy or eculizumab, the worst prognosis is in factor H-HUS, as mortality can reach 20% and 50% of survivors do not recover renal function. Half of factor I-HUS progress to end-stage renal failure. Conversely, most patients with MCP-HUS have preserved renal function. Anti-factor H antibodies-HUS has favourable outcome if treated early.

Successful renal transplantation in a patient with atypical hemolytic uremic syndrome carrying mutations in both factor I and MCP

Kidney transplantation in patients with atypical hemolytic uremic syndrome (aHUS) carrying mutations in the soluble complement regulators factor H (CFH) or factor I (CFI) is associated with elevated risk of disease recurrence and almost certain graft loss. In contrast, recurrence is unusual in patients with mutations in the membrane-associated complement regulator membrane cofactor protein (MCP) (CD46). Therefore, a panel of experts recently recommended the combined liver-kidney transplantation to minimize aHUS recurrence in patients with mutations in CFH or CFI. There was, however, very limited information regarding transplantation in patients carrying mutations in both soluble and membrane-associated complement regulators to support a recommendation. Here, we report the case of an aHUS patient with a heterozygous mutation in both CFI and MCP who received an isolated kidney transplant expressing normal MCP levels. Critically, the patient suffered from a severe antibody-mediated rejection that was successfully treated with plasmapheresis and IvIgG. Most important, despite the complement activation in the allograft, there was no evidence of thrombotic microangiopathy, suggesting that the normal MCP levels in the grafted kidney were sufficient to prevent the aHUS recurrence. Our results suggest that isolated kidney transplantation may be a good first option for care in aHUS patients carrying CFI/MCP combined heterozygous mutations.

Belatacept as maintenance immunosuppression for postrenal transplant de novo drug-induced thrombotic microangiopathy

De novo posttransplant thrombotic microangiopathy (TMA) is a complication of solid organ transplantation, which remains difficult to treat. In many cases, immunosuppressants and particularly calcineurin inhibitors, trigger TMA. Although withdrawing the offending drug may lead to resolution of TMA, graft and patient outcomes are poor. Specific treatments, including plasma exchange, have not gained widespread acceptance in those with fulminant disease and new approaches to the condition are urgently needed. We report a case of posttransplant de novo TMA presenting serially in association with ciclosporin, tacrolimus and sirolimus in a young recipient of a living donor kidney transplant. We describe a patient treated with belatacept, a novel CTLA4 Ig fusion protein, as ongoing maintenance immunosuppression to allow avoidance of conventional agents once associated with TMA. We report excellent early graft outcome, with no adverse events using this strategy. We suggest that belatacept may have a role in this traditionally difficult-to-treat group of patients.

Recovery of tacrolimus-associated brachial neuritis after conversion to everolimus in a pediatric renal transplant recipient--case report and review of the literature

TAC has been shown to be a potent immunosuppressive agent for solid organ transplantation in pediatrics. Neurotoxicity is a potentially serious toxic effect. It is characterized by encephalopathy, headaches, seizures, or neurological deficits. Here, we describe an eight-and-a-half-yr-old male renal transplant recipient with right BN. MRI demonstrated hyperintense T2 signals in the cervical cord and right brachial plexus roots indicative of both myelitis and right brachial plexitis. Symptoms persisted for three months despite TAC dose reduction, administration of IVIG and four doses of methylprednisolone pulse therapy. Improvement and eventually full recovery only occurred after TAC was completely discontinued and successfully replaced by everolimus.

Complement mutation-associated de novo thrombotic microangiopathy following kidney transplantation

Mutations in one or more genes encoding complement-regulatory proteins predispose to atypical hemolytic uremic syndrome (aHUS) and its recurrence following kidney transplantation. We evaluated plasma complement level and performed a screening for mutations in genes encoding complement Factors H and I (CFH, CFI) and membrane cofactor protein (MCP) in 24 kidney transplant recipients experiencing de novo thrombotic microangiopathy (TMA). Six patients presented with low C3 and/or low Factor B levels suggestive complement alternative pathway. A mutation in the CFH or CFI gene was found in 7/24 patients (29%), two of whom had a mutation in both genes. On the contrary, no mutation was identified in a control kidney transplant patients group (n = 25) without TMA. Patients with or without mutations were similar with regard to clinical features. Eight out of 24 patients lost their graft within 1 year of posttransplantation including six patients with a CFH mutation or a decrease of C3 or CFB in plasma. To conclude, kidney transplant patients with de novo TMA exhibit an unexpectedly high frequency of CFH and CFI mutations. These results suggest that genetic abnormalities may represent risk factors for de novo TMA after kidney transplantation and raise the question of the best therapeutic strategy.

Retinal injury as an early manifestation of posttransplant thrombotic microangiopathy: recovery with plasma exchanges and conversion to sirolimus--case report and review of the literature

Thrombotic microangiopathy (TMA) remains a serious event. We report a case of occurrence of TMA in the immediate postoperative period after a living-related renal transplantation. A distinguished feature of the case was major, early involvement of the retina with marked by decreased visual acuity along with thrombocytopenia and renal functional impairment. The syndrome was reversible with plasma exchange and conversion from tacrolimus to sirolimus. The patient's renal function is excellent at 11 months after transplantation. Decreased visual acuity and cotton wool exudates may be the first manifestation of posttransplant TMA.

Thrombotic microangiopathy after simultaneous pancreas?kidney transplantation

Thrombotic microangiopathy (TMA) is rare after transplantation and is associated with a high incidence of kidney graft dysfunction. Between December 2000 and March 2006, 136 simultaneous pancreas-kidney transplantations were performed with an incidence of TMA of 5.1% (71.4% localized to kidney allograft). All cases were diagnosed during the first three months and were attributed to tacrolimus; 74% were women. Systemic TMA presented higher values of lactate dehydrogenase (2658 +/- 659 U/L vs. 1331 +/- 473 U/L, p = 0.04) and a greater decrease in hematocrit (45.8 +/- 17.7% vs. 19.2 +/- 6%, p = 0.02) than in localized TMA. Acute kidney rejection complicated almost 90% of the cases with 43% of kidney graft lost. Tacrolimus was switched to sirolimus and fresh-frozen plasma was administered. Creatinine clearance after a mean follow-up of two yr was 100.7 mL/min/1.73 m(2) and 57.9 mL/min/1.73 m(2) in patients with systemic and localized TMA, respectively. In conclusion, sirolimus is an alternative to TMA associated with tacrolimus.

Thrombotic microangiopathy after kidney transplantation

Two forms of post-transplant thrombotic microangiopathy (TMA) may be recognized: recurrent TMA and de novo TMA. Recurrent TMA may occur in patients who developed a nondiarrhoeal form of haemolytic uraemic syndrome (HUS) being particularly frequent in patients with autosomal recessive or dominant HUS. The recurrence is almost the rule in patients with mutation in complement factor H gene. Most patients eventually lose the graft. Treatment with plasma infusions or plasmapheresis is often disappointing, but few cases may be rescued. Intravenous immunoglobulins and rituximab have also been successful in anedoctic cases. De novo TMA is rarer. A number of factors including viral infection may be responsible of de novo TMA, but in most cases TMA is triggered by calcineurin inhibitors or mTOR inhibitors. The clinical presentation of de novo TMA may be variable with some patients showing clinical and laboratory features of HUS while others showing only a progressive renal failure. The prognosis is less severe than with recurrent TMA. Complete withdrawal of the offending drug may lead to improvement in many cases. The addition of plasma exchange may result in graft salvage in about 80% of cases.

Clinical Outcome of Thrombotic Microangiopathy after Living-Donor Liver Transplantation Treated with Plasma Exchange Therapy

Thrombotic microangiopathy (TMA) is a well-documented but severe complication that occurs after solid-organ transplant. Administration of calcineurin inhibitors is considered a major cause of this fatal complication; prompt initiation of plasma exchange therapy after reduction or conversion of calcineurin inhibitors has been recommended. Nevertheless, little is known about clinical evidence of this strategy against TMA after solid-organ, especially non-renal-organ, transplantation. Medical records of 63 patients who were hospitalized at Artificial Organ and Transplantation Division in Tokyo University Hospital and underwent blood purification therapy between January 1999 and May 2005 were reviewed. Twenty-eight living-donor liver transplantation (LDLT) recipients who received plasma exchange therapy were identified, and 18 of them were found retrospectively to receive a diagnosis of having TMA. Of the 18 patients, 10 (56%) responded to this therapy and survived after the treatment was stopped, whereas eight (44%) patients died before improvement. Subsequent follow-up of patients clarified that 1-yr survival rate of post-LDLT TMA was approximately 30%. Multivariate Cox proportional-hazards regression analysis demonstrated that the interval between transplant surgery and onset of TMA (hazard ratio 1.35 per 30 d; 95% confidence interval 1.07 to 1.71; P = 0.021) and pretreatment blood urea nitrogen level (hazard ratio 1.39 per 10 mg/dl; 95% confidence interval 1.02 to 1.90; P = 0.037) predicted mortality. Analyses identified post-LDLT recipients with TMA as being at high risk for poor prognosis. Effective strategies are needed for late-onset TMA after LDLT to improve treatment response and survival.