Eculizumab as rescue therapy for atypical hemolytic uremic syndrome with normal platelet count

Atypical hemolytic uremic syndrome: Consensus of diagnosis and treatment in Taiwan

Atypical hemolytic uremic syndrome (aHUS), characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, is a rare but life-threatening systemic disorder caused by the dysregulation of the complement pathway. Current advances in molecular analysis and pathogenesis have facilitated the establishment of diagnosis and development of effective complement blockade. Based on this recent consensus, we provide suggestions regarding the diagnosis and management of aHUS in Taiwan. The diagnosis of aHUS is made by the presence of TMA with normal ADAMTS13 activity without known secondary causes. Although only 60% of patients with aHUS have mutations in genes involving the compliment and coagulation systems, molecular analysis is suggestive for helping establish diagnosis, clarifying the underlying pathophysiology, guiding the treatment decision-making, predicting the prognosis, and deciding renal transplantation. Complement blockade, anti-C5 monoclonal antibody, is the first-line therapy for patients with aHUS. Plasma therapy should be considered for removing autoantibody in patients with atypical HUS caused by anti-CFH or complement inhibitor is unavailable.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice-Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating, and categorizing indications for the evidence-based use of therapeutic apheresis in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the Committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

Serological and genetic complement alterations in infection-induced and complement-mediated hemolytic uremic syndrome

BACKGROUND

The role of complement in the atypical form of hemolytic uremic syndrome (aHUS) has been investigated extensively in recent years. As the HUS-associated bacteria Shiga-toxin-producing Escherichia coli (STEC) can evade the complement system, we hypothesized that complement dysregulation is also important in infection-induced HUS.

METHODS

Serological profiles (C3, FH, FI, AP activity, C3d, C3bBbP, C3b/c, TCC, αFH) and genetic profiles (CFH, CFI, CD46, CFB, C3) of the alternative complement pathway were prospectively determined in the acute and convalescent phase of disease in children newly diagnosed with STEC-HUS or aHUS. Serological profiles were compared with those of 90 age-matched controls.

RESULTS

Thirty-seven patients were studied (26 STEC-HUS, 11 aHUS). In 39 % of them, including 28 % of STEC-HUS patients, we identified a genetic and/or acquired complement abnormality. In all patient groups, the levels of investigated alternative pathway (AP) activation markers were elevated in the acute phase and normalized in remission. The levels were significantly higher in aHUS than in STEC-HUS patients.

CONCLUSIONS

In both infection-induced HUS and aHUS patients, complement is activated in the acute phase of the disease but not during remission. The C3d/C3 ratio displayed the best discrepancy between acute and convalescent phase and between STEC-HUS and aHUS and might therefore be used as a biomarker in disease diagnosis and monitoring. The presence of aberrations in the alternative complement pathway in STEC-HUS patients was remarkable, as well.

First-Line, Early and Long-Term Eculizumab Therapy in Atypical Hemolytic Uremic Syndrome: A Case Series in Pediatric Patients

INTRODUCTION

Studies relating to first-line, early, and long-term eculizumab treatment and outcomes in children with atypical hemolytic uremic syndrome (aHUS) are scarce and unclear. The aim of this case-series study was to evaluate the outcomes of first-line, early, and long-term eculizumab treatment in our aHUS patients.

MATERIALS AND METHODS

We reviewed the data from four pediatric patients with aHUS who were treated with eculizumab. In three of them, eculizumab was used as a first-line therapy, and the follow-up period was ≥2 years in three patients.

RESULTS

Plasma exchange could not be performed in any patient. Plasma infusions were used only in Patient 1 (a 14-month-old boy) for 8 days without any response. Therefore, eculizumab was started on day 11 after admission. Patient 2 (a 16-month-old boy), Patient 3 (an 11-year-old girl), and Patient 4 (a 32-month-old girl) were treated with eculizumab as a first-line therapy, which was started 2-4 days after admission. The dosage of eculizumab was adjusted according to body weight. The hematologic parameters (the time frames were 3-17 days) and C ₃ (the time frames were 10-17 days) returned to normal in all patients after receipt of eculizumab. Although Patient 1 developed stage III chronic kidney disease, complete renal recovery occurred in Patients 2 and 4. Patient 3 also had reflux nephropathy with bilateral grade III vesicoureteral reflux and renal scars. Her creatinine clearance returned to the baseline value after receiving eculizumab. No complications related to eculizumab were observed in any patient during the follow-up period.

CONCLUSION

Eculizumab can be successfully used as a first-line therapy in pediatric aHUS patients. We observed that the early initiation of eculizumab was associated with the complete recovery of renal function.

Critical appraisal of eculizumab for atypical hemolytic uremic syndrome

The biology of atypical hemolytic uremic syndrome has been shown to involve inability to limit activation of the alternative complement pathway, with subsequent damage to systemic endothelial beds and the vasculature, resulting in the prototypic findings of a thrombotic microangiopathy. Central to this process is the formation of the terminal membrane attack complex C5b-9. Recently, application of a monoclonal antibody that specifically binds to C5, eculizumab, became available to treat patients with atypical hemolytic uremic syndrome, replacing plasma exchange or infusion as primary therapy. This review focuses on the evidence, based on published clinical trials, case series, and case reports, on the efficacy and safety of this approach.

Improved renal recovery in patients with atypical hemolytic uremic syndrome following rapid initiation of eculizumab treatment

Background

Eculizumab is approved for atypical hemolytic uremic syndrome (aHUS). Guidelines discuss the importance of prompt treatment. We report a post hoc analysis investigating the effect of baseline factors, including patient characteristics and time from the latest aHUS manifestation to eculizumab initiation, on change from baseline in estimated glomerular filtration rate (eGFR) and other outcomes.

Methods

Data were pooled from four phase 2, open-label, single-arm, prospective clinical studies of eculizumab for patients with aHUS. Multivariate regressions identified predictors of eGFR change from baseline. The proportion of patients achieving sustained eGFR increase (defined: ≥15 ml/min/1.73 m² for ≥28 days) and platelet count normalization were evaluated 1 year post-treatment. Baseline characteristics and eGFR outcomes were summarized by time to treatment from last aHUS manifestation [≤7 days (n = 21) versus >7 days (n = 76)].

Results

Baseline eGFR were similar between groups. Multivariate regression analysis demonstrated time from aHUS manifestation to eculizumab treatment, age, baseline lactate dehydrogenase (LDH) and baseline hemoglobin were independently predictive of eGFR change from baseline. Mean eGFR change from baseline at 1 year was significantly higher in patients treated in ≤7 days than >7 days (57 vs. 23 ml/min/1.73 m², p = 0.0098). After 1 year, 17/21 and 36/76 patients in the ≤7 and >7 day groups, respectively, achieved a sustained increase in eGFR. Mean time to platelet count normalization was similar between groups.

Conclusions

Younger age, higher baseline LDH and lower baseline hemoglobin were associated with greater eGFR improvements. Early eculizumab initiation led to improved renal recovery, demonstrating the importance of rapid diagnosis and treatment of patients with aHUS.

Electronic supplementary material

The online version of this article (doi:10.1007/s40620-016-0288-3) contains supplementary material, which is available to authorized users.

Eculizumab is a safe and effective treatment in pediatric patients with atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is caused by alternative complement pathway dysregulation, leading to systemic thrombotic microangiopathy (TMA) and severe end-organ damage. Based on 2 prospective studies in mostly adults and retrospective data in children, eculizumab, a terminal complement inhibitor, is approved for aHUS treatment. Here we prospectively evaluated efficacy and safety of weight-based dosing of eculizumab in eligible pediatric patients with aHUS in an open-label phase II study. The primary end point was complete TMA response by 26 weeks. Twenty-two patients (aged 5 months-17 years) were treated; 16 were newly diagnosed, 12 had no prior plasma exchange/infusion during current TMA symptomatology, 11 received baseline dialysis and 2 had prior renal transplants. By week 26, 14 achieved a complete TMA response, 18 achieved hematologic normalization, and 16 had 25% or better improvement in serum creatinine. Plasma exchange/infusion was discontinued in all, and 9 of the 11 patients who required dialysis at baseline discontinued, whereas none initiated new dialysis. Eculizumab was well tolerated; no deaths or meningococcal infections occurred. Bone marrow failure, wrist fracture, and acute respiratory failure were reported as unrelated severe adverse events. Thus, our findings establish the efficacy and safety of eculizumab for pediatric patients with aHUS and are consistent with proposed immediate eculizumab initiation following diagnosis in children.

An update for atypical haemolytic uraemic syndrome: diagnosis and treatment. A consensus document

Haemolytic uraemic syndrome (HUS) is a clinical entity defined as the triad of nonimmune haemolytic anaemia, thrombocytopenia, and acute renal failure, in which the underlying lesions are mediated by systemic thrombotic microangiopathy (TMA). Different causes can induce the TMA process that characterizes HUS. In this document we consider atypical HUS (aHUS) a sub-type of HUS in which the TMA phenomena are the consequence of the endotelial damage in the microvasculature of the kidneys and other organs due to a disregulation of the activity of the complement system. In recent years, a variety of aHUs-related mutations have been identified in genes of the the complement system, which can explain approximately 60% of the aHUS cases, and a number of mutations and polymorphisms have been functionally characterized. These findings have stablished that aHUS is a consequence of the insufficient regulation of the activiation of the complement on cell surfaces, leading to endotelial damage mediated by C5 and the complement terminal pathway. Eculizumab is a monoclonal antibody that inhibits the activation of C5 and blocks the generation of the pro-inflammatory molecule C5a and the formation of the cell membrane attack complex. In prospective studies in patients with aHUS, the use of Eculizumab has shown a fast and sustained interruption of the TMA process and it has been associated with significative long-term improvements in renal function, the interruption of plasma therapy and important reductions in the need of dialysis. According to the existing literature and the accumulated clinical experience, the Spanish aHUS Group published a consensus document with recommendations for the treatment of aHUs (Nefrologia 2013;33[1]:27-45). In the current online version of this document, we update the aetiological classification of TMAs, the pathophysiology of aHUS, its differential diagnosis and its therapeutic management.

Advances and challenges in the management of complement-mediated thrombotic microangiopathies

Complement activation plays a major role in several renal pathophysiological conditions. The three pathways of complement lead to C3 activation, followed by the formation of the anaphylatoxin C5a and the terminal membrane attack complex (MAC) in blood and at complement activating surfaces, lead to a cascade of events responsible for inflammation and for the induction of cell lysis. In case of ongoing uncontrolled complement activation, endothelial cells activation takes place, leading to events in which at the end thrombotic microangiopathy can occur. Atypical haemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy characterized by excessive complement activation on the surface of the microcirculation. It is a severe, rare disease which leads to end-stage renal failure (ESRF) and/or to death in more than 50% of patients without treatment. In the first decade of the second millennium, huge progress in understanding the aetiology of this disease was made, which paved the way to better treatment. First, protocols of plasma therapy for treatment, prevention of relapses and for renal transplantation in those patients were set up. Secondly, in some severe cases, combined kidney and liver transplantation was reported. Finally, at the end of this decade, the era of complement inhibitors, as anti-C5 monoclonal antibody (anti-C5 mAb) began. The past five years have seen growing evidence of the favourable effect of anti-C5 mAb in aHUS which has made this drug the first-line treatment in this disease. The possible complication of meningococcal infection needs appropriate vaccination before its use. Unfortunately, the worldwide use of anti-C5 mAb is limited by its very high price. In the future, extension of indications for anti-C5 mAb use, the elaboration of generics and of mAbs directed towards other complement factors of the terminal pathway of the complement system might succeed in reducing the cost of this new valuable therapeutic approach and render it available worldwide for patients from all social classes.

Atypical aHUS: State of the art

Tremendous advances in our understanding of the thrombotic microangiopathies (TMAs) have revealed distinct disease mechanisms within this heterogeneous group of diseases. As a direct result of this knowledge, both children and adults with complement-mediated TMA now enjoy higher expectations for long-term health. In this update on atypical hemolytic uremic syndrome, we review the clinical characteristics; the genetic and acquired drivers of disease; the broad spectrum of environmental triggers; and current diagnosis and treatment options. Many questions remain to be addressed if additional improvements in patient care and outcome are to be achieved in the coming decade.

Eculizumab in the treatment of atypical hemolytic uremic syndrome in an infant leads to cessation of peritoneal dialysis and improvement of severe hypertension

BACKGROUND

Severe hypertension (HTN) and acute kidney injury frequently associated with atypical hemolytic uremic syndrome (aHUS) were refractory to various therapies in the pre-eculizumab era. Here we report the case of a 4-month-old boy who developed aHUS presenting with undetectable C3 protein, no predisposing mutations in complement factors, and no antibodies against factor H.

METHODS

Repeated plasma infusions and nine sessions of plasmapheresis were ineffective. The patient initially required continuous hemodiafiltration and thereafter peritoneal dialysis. Despite vigorous antihypertensive treatment and improved fluid overload with dialysis, HTN persisted. His low C3 level (<20 mg/dl) suggested unrestricted complement activation. Therefore, based on the suspicion of unrestricted complement cascade in the pathogenesis, treatment with eculizumab, a human anti-C5 monoclonal antibody, was initiated with the aim of controlling disease activity.

RESULTS

Eculizumab therapy resulted in the control of severe HTN and cessation of peritoneal dialysis.

CONCLUSIONS

This infant with HTN and acute kidney injury associated with aHUS was treated successfully with eculizumab.

Remission of aHUS neurological damage with eculizumab

Atypical haemolytic uraemic syndrome (aHUS) is a rare disease characterized by haemolytic microangiopathic anaemia, thrombocytopaenia and acute onset of renal failure, in the absence of Escherichia coli infection. Renal damage usually progresses to end-stage renal disease (ESRD), sometimes being accompanied by signs of extrarenal thrombotic microangiopathy (TMA). We report a case of full neurological and haematological recovery after eculizumab treatment in a patient with ESRD secondary to chronic aHUS refractory to plasmatherapy while she was under dialysis. It highlights the use of eculizumab for controlling extrarenal manifestations of aHUS in this population.

An audit analysis of a guideline for the investigation and initial therapy of diarrhea negative (atypical) hemolytic uremic syndrome

BACKGROUND

In 2009, the European Paediatric Study Group for Haemolytic Uraemic Syndrome (HUS) published a clinical practice guideline for the investigation and initial therapy of diarrhea-negative HUS (now more widely referred to as atypical HUS, aHUS). The therapeutic component of the guideline (comprising early, high-volume plasmapheresis) was derived from anecdotal evidence and expert consensus, and the authors committed to auditing outcome.

METHODS

Questionnaires were distributed to pediatric nephrologists across Europe, North America, and the Middle East, who were asked to complete one questionnaire per patient episode of aHUS between July 1, 2009 and December 31, 2010. Comprehensive, anonymous demographic and clinical data were collected.

RESULTS

Seventy-one children were reported with an episode of aHUS during the audit period. Six cases occurred on a background of influenza A H1N1 infection. Of 71 patients, 59 (83 %) received plasma therapy within the first 33 days, of whom ten received plasma infusion only. Complications of central venous catheters occurred in 16 out of 51 patients with a catheter in-situ (31 %). Median time to enter hematological remission was 11.5 days, and eight of 71 (11 %) patients did not enter hematological remission by day 33. Twelve patients (17 %) remained dialysis dependent at day 33.

CONCLUSIONS

This audit provides a snapshot of the early outcome of a group of children with aHUS in the months prior to more widespread use of eculizumab.

An audit analysis of a guideline for the investigation and initial therapy of diarrhea negative (atypical) hemolytic uremic syndrome

BACKGROUND

In 2009, the European Paediatric Study Group for Haemolytic Uraemic Syndrome (HUS) published a clinical practice guideline for the investigation and initial therapy of diarrhea-negative HUS (now more widely referred to as atypical HUS, aHUS). The therapeutic component of the guideline (comprising early, high-volume plasmapheresis) was derived from anecdotal evidence and expert consensus, and the authors committed to auditing outcome.

METHODS

Questionnaires were distributed to pediatric nephrologists across Europe, North America, and the Middle East, who were asked to complete one questionnaire per patient episode of aHUS between July 1, 2009 and December 31, 2010. Comprehensive, anonymous demographic and clinical data were collected.

RESULTS

Seventy-one children were reported with an episode of aHUS during the audit period. Six cases occurred on a background of influenza A H1N1 infection. Of 71 patients, 59 (83 %) received plasma therapy within the first 33 days, of whom ten received plasma infusion only. Complications of central venous catheters occurred in 16 out of 51 patients with a catheter in-situ (31 %). Median time to enter hematological remission was 11.5 days, and eight of 71 (11 %) patients did not enter hematological remission by day 33. Twelve patients (17 %) remained dialysis dependent at day 33.

CONCLUSIONS

This audit provides a snapshot of the early outcome of a group of children with aHUS in the months prior to more widespread use of eculizumab.

Eculizumab: a review of its use in atypical haemolytic uraemic syndrome

The recombinant humanized monoclonal antibody eculizumab (Soliris(®)) is a complement inhibitor that is indicated for use in the treatment of atypical haemolytic uraemic syndrome (aHUS). This article reviews the clinical efficacy and tolerability of eculizumab in the treatment of patients with aHUS, as well as summarizing its pharmacological properties. Intravenous eculizumab inhibited complement-mediated thrombotic microangiopathy in patients aged ≥12 years with aHUS, according to the results of two noncomparative, multinational, 26-week, phase II trials. At 26 weeks, the platelet count was significantly increased in patients with progressing thrombotic microangiopathy despite plasma exchange/infusion, and thrombotic microangiopathic event-free status was achieved in 80 % of patients with a long disease duration and chronic kidney disease who received long-term plasma exchange/infusion. Renal function and health-related quality of life also improved with eculizumab therapy in both studies. Outcomes were maintained or further improved throughout 2 years of follow-up. Eculizumab was also effective in adult and paediatric patients with aHUS, according to the results of additional prospective or retrospective trials. Intravenous eculizumab was generally well tolerated in patients with aHUS. Eculizumab is associated with an increased susceptibility to meningococcal infection, so patients should be immunized with meningococcal vaccine. In conclusion, eculizumab is a valuable new agent for use in the treatment of aHUS.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The atypical form of HUS is a disease characterized by complement overactivation. Inherited defects in complement genes and acquired autoantibodies against complement regulatory proteins have been described. Incomplete penetrance of mutations in all predisposing genes is reported, suggesting that a precipitating event or trigger is required to unmask the complement regulatory deficiency. The underlying genetic defect predicts the prognosis both in native kidneys and after renal transplantation. The successful trials of the complement inhibitor eculizumab in the treatment of atypical HUS will revolutionize disease management.

Eculizumab as first-line therapy for atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a genetic, life-threatening, chronic disease that can affect patients of all ages. aHUS is caused by uncontrolled complement activation due to genetic defects of complement regulation. Plasma exchange or infusion has been used to manage aHUS and may transiently maintain hematologic variables in some patients, but as the underlying complement dysregulation persists, end-stage renal disease or death occurs in 33% to 40% of patients during the first clinical manifestation. Here we present a pediatric case showing that first-line eculizumab treatment successfully blocked the progression of thrombotic microangiopathy in aHUS.

Complement therapy in atypical haemolytic uraemic syndrome (aHUS)

Central to the pathogenesis of atypical haemolytic uraemic syndrome (aHUS) is over-activation of the alternative pathway of complement. Inherited defects in complement genes and autoantibodies against complement regulatory proteins have been described. The use of plasma exchange to replace non-functioning complement regulators and hyper-functional complement components in addition to the removal of CFH-autoantibodies made this the ‘gold-standard’ for management of aHUS. In the last 4 years the introduction of the complement inhibitor Eculizumab has revolutionised the management of aHUS. In this review we shall discuss the available literature on treatment strategies to date.

Thrombocytopenia is not mandatory to diagnose haemolytic and uremic syndrome

BACKGROUND

Hemolytic and uremic syndrome (HUS) diagnosis involves association of non immune hemolytic anemia, thrombocytopenia, and renal failure. HUS without thrombocytopenia has been observed, we call it partial HUS. Its real frequency and outcome are unknown. The aim of this study was to determine the prevalence of patients with normal platelets count in two HUS cohorts and to compare their outcome to patients with thrombocytopenia.

METHODS

We retrospectively identified HUS diagnosis in two different cohorts. The first cohort was from a single center and consisted of all cases of HUS whatever the aetiology, the second was multicentric and consisted of atypical HUS patients. These cohorts were divided into two groups depending on the presence or absence of thrombocytopenia. Clinical and biological data were compared between thrombopenic and non thrombopenic group.

RESULTS

We identified 13% (20/150) of patients with normal platelets count: 10 episodes (18%) of HUS in six patients (14%) in the monocentric cohort and 14 patients (13%) with 17 episodes (12%) in the multicentric cohort of atypical HUS. Groups differed in platelets count and LDH level. In both cohorts, renal outcome was similar to patient presenting with thrombocytopenia.

CONCLUSION

HUS with normal platelets count is not infrequent. Relative to classical clinical presentation of HUS, partial HUS has similar characteristics and identical poor renal outcome and so must be treated in the same way.

Thrombocytopenia is not mandatory to diagnose haemolytic and uremic syndrome

BACKGROUND

Hemolytic and uremic syndrome (HUS) diagnosis involves association of non immune hemolytic anemia, thrombocytopenia, and renal failure. HUS without thrombocytopenia has been observed, we call it partial HUS. Its real frequency and outcome are unknown. The aim of this study was to determine the prevalence of patients with normal platelets count in two HUS cohorts and to compare their outcome to patients with thrombocytopenia.

METHODS

We retrospectively identified HUS diagnosis in two different cohorts. The first cohort was from a single center and consisted of all cases of HUS whatever the aetiology, the second was multicentric and consisted of atypical HUS patients. These cohorts were divided into two groups depending on the presence or absence of thrombocytopenia. Clinical and biological data were compared between thrombopenic and non thrombopenic group.

RESULTS

We identified 13% (20/150) of patients with normal platelets count: 10 episodes (18%) of HUS in six patients (14%) in the monocentric cohort and 14 patients (13%) with 17 episodes (12%) in the multicentric cohort of atypical HUS. Groups differed in platelets count and LDH level. In both cohorts, renal outcome was similar to patient presenting with thrombocytopenia.

CONCLUSION

HUS with normal platelets count is not infrequent. Relative to classical clinical presentation of HUS, partial HUS has similar characteristics and identical poor renal outcome and so must be treated in the same way.

Eculizumab for atypical hemolytic uremic syndrome recurrence in renal transplantation

Eculizumab (anti-C5) has been sporadically reported as an efficient therapy for atypical hemolytic uremic syndrome (aHUS). However, the lack of series precludes any firm conclusion about the optimal use of anti-C5 for preventing or treating aHUS posttransplant aHUS recurrence. We thoroughly studied 22 renal transplant recipients with aHUS who received off-label therapy with anti-C5, including 12 cases, which have not been reported yet. Nine patients, all carrying a complement genetic abnormality associated with a high risk of aHUS recurrence, received prophylactic anti-C5 therapy to prevent posttransplant recurrence. Eight of them had a successful recurrence-free posttransplant course and achieved a satisfactory graft function, while the remaining patient experienced early arterial thrombosis of the graft. Thirteen renal transplant recipients were given anti-C5 for posttransplant aHUS recurrence. A complete reversal of aHUS activity was obtained in all of them. Importantly, the delay of anti-C5 initiation after the onset of the aHUS episode inversely correlated with the degree of renal function improvement. Three patients in whom anti-C5 was subsequently stopped experienced a relapse. Altogether these data suggest that long-term eculizumab is highly effective for preventing and treating posttransplant aHUS recurrence. Our study also indicates that anti-C5 should be promptly started if a recurrence occurs.

Use of eculizumab for atypical haemolytic uraemic syndrome and C3 glomerulopathies

In the past decade, a large body of evidence has accumulated in support of the critical role of dysregulation of the alternative complement pathway in atypical haemolytic uraemic syndrome (aHUS) and C3 glomerulopathies. These findings have paved the way for innovative therapeutic strategies based on complement blockade, and eculizumab, a monoclonal antibody targeting the human complement component 5, is now widely used to treat aHUS. In this article, we review 28 case reports and preliminary data from 37 patients enrolled in prospective trials of eculizumab treatment for episodes of aHUS involving either native or transplanted kidneys. Eculizumab may be considered as an optimal first-line therapy when the diagnosis of aHUS is unequivocal and this treatment has the potential to rescue renal function when administered early after onset of the disease. However, a number of important issues require further study, including the appropriate duration of treatment according to an individual's genetic background and medical history, the optimal strategy to prevent post-transplantation recurrence of aHUS and a cost-efficacy analysis. Data regarding the efficacy of eculizumab in the control of C3 glomerulopathies are more limited and less clear, but several observations suggest that eculizumab may act on the most inflammatory forms of this disorder.

Thrombotic microangiopathy and associated renal disorders

Thrombotic microangiopathy (TMA) is a pathological process involving thrombocytopenia, microangiopathic haemolytic anaemia and microvascular occlusion. TMA is common to haemolytic uraemic syndrome (HUS) associated with shiga toxin or invasive pneumococcal infection, atypical HUS (aHUS), thrombotic thrombocytopenic purpura (TTP) and other disorders including malignant hypertension. HUS complicating infection with shiga toxin-producing Escherichia coli (STEC) is a significant cause of acute renal failure in children worldwide, occurring sporadically or in epidemics. Studies in aHUS have revealed genetic and acquired factors leading to dysregulation of the alternative complement pathway. TTP has been linked to reduced activity of the ADAMTS13 cleaving protease (typically with an autoantibody to ADAMTS13) with consequent disruption of von Willebrand factor multimer processing. However, the convergence of pathogenic pathways and clinical overlap create diagnostic uncertainty, especially at initial presentation. Furthermore, recent developments are challenging established management protocols. This review addresses the current understanding of molecular mechanisms underlying TMA, relating these to clinical presentation with an emphasis on renal manifestations. A diagnostic and therapeutic approach is presented, based on international guidelines, disease registries and published trials. Early treatment remains largely empirical, consisting of plasma replacement/exchange with the exception of childhood STEC-HUS or pneumococcal sepsis. Emerging therapies such as the complement C5 inhibitor eculizumab for aHUS and rituximab for TTP are discussed, as is renal transplantation for those patients who become dialysis-dependent as a result of aHUS.