Eculizumab induces long-term remission in recurrent post-transplant HUS associated with C3 gene mutation

Atypical hemolytic uremic syndrome with a C3 variant following COVID-19: a case report

Atypical hemolytic uremic syndrome (aHUS) is a form of thrombotic microangiopathy (TMA) characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, and is caused by overactivation of the alternative complement pathway. A 13-year-old Japanese boy with an unremarkable medical history developed symptoms of TMA following coronavirus disease 2019 (COVID-19) infection with mild respiratory symptoms. He was eventually diagnosed with aHUS with a gain-of-function C3 variant. He improved with supportive therapy and plasma exchange, and did not require anti-C5 antibody therapy. In the literature, more than 20 cases of de novo or relapsed aHUS have been described following COVID-19. It has been shown that the complement lectin pathway can be activated by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike and N proteins, and the alternative pathway can be activated by the SARS-CoV-2 spike protein. The current case highlights the possibility that COVID-19, even when respiratory symptoms are not severe, can trigger aHUS.

Recurrent complement-mediated Hemolytic uremic syndrome after kidney transplantation

Hereditary forms of hemolytic uremic syndrome (HUS), formerly known as atypical HUS, typically involve mutations in genes encoding for components of the alternative pathway of complement, therefore they are often referred to as complement-mediated HUS (cHUS). This condition has a high risk of recurrence in the transplanted kidney, leading to accelerated graft loss. The availability of anti-complement component C5 antibody eculizumab has enabled successful transplantation with a notably reduced recurrence rate and improved prognosis. Open questions are related to the potential for complement inhibitor discontinuation, ideal timing of treatment withdrawal, and patient selection based on genetic abnormalities. Our review delves into the pathophysiology, classification, genetic predispositions, and management strategies for cHUS in the native and transplant kidneys.

Ex Vivo Test of Complement Dysregulation in Atypical Hemolytic Uremic Syndrome Kidney Transplant patients: A Pilot Study

Introduction

In 2014, a complement assay, which evaluates C5b-9 deposition on endothelial cells, was proposed as a biomarker for atypical hemolytic uremic syndrome (aHUS). Early diagnosis and/or prediction of aHUS (relapse) is pivotal in aHUS kidney transplant recipients who do not receive eculizumab prophylaxis.

Methods

In this pilot study, serum samples of transplanted patients with aHUS in remission without eculizumab and patients with other primary kidney diseases (controls) were blinded and evaluated in the complement assay.

Results

We included 13 patients with aHUS (4 males, 9 females) of median age of 54 years (range: 35-69) and median of 5.9 years (range: 0.25-14.1) after transplantation; and 13 controls (7 males, 6 females) of median age of 42 years (range: 27-60) and median of 5.8 years (range: 1.6-11.7) after transplantation. There were no significant differences in C5b-9 deposits between patients with aHUS and controls on resting cells (median of 136% [range: 93%-382%] and 121% [range: 75%-200%], respectively) and activated cells (median of 196% [range: 99%-388%] and 170% [range: 113%-260%], respectively). Three patients with aHUS and 4 controls showed elevated C5b-9 deposits on resting cells, which should correspond to active aHUS. None of these patients had laboratory signs of thrombotic microangiopathy (TMA). During follow-up (15.8 months, range: 6-21), estimated glomerular filtration rate remained stable in all. In 5 patients with aHUS with a genetic variant, no increase in C5b-9 deposits was found on activated endothelial cells, which contrasts with the literature suggesting that the test should identify carriers of a genetic variant.

Conclusion

Our data question the routine use of the ex vivo complement assay in kidney transplant patients. Future studies should evaluate the test characteristics of assay in kidney transplant patients.

Eculizumab Rescue Therapy in Patients with Recurrent Atypical Hemolytic Uremic Syndrome After Kidney Transplantation

Introduction

Since 2016, kidney transplantation in patients with atypical hemolytic uremic syndrome (aHUS) in the Netherlands is performed without eculizumab prophylaxis. Eculizumab is given in case of posttransplant aHUS recurrence. Eculizumab therapy is monitored in the CUREiHUS study.

Methods

All participating kidney transplant patients who received eculizumab therapy for a suspected posttransplant aHUS recurrence were evaluated. Overall recurrence rate was monitored prospectively at Radboud University Medical Center.

Results

In the period from January 2016 until October 2020, we included 15 (12 females, 3 males; median age 42 years, range 24-66 years) patients with suspected aHUS recurrence after kidney transplantation in this study. The time interval to recurrence showed a bimodal distribution. Seven patients presented early after transplantation (median 3 months, range 0.3-8.8 months), with typical aHUS features: rapid loss of estimated glomerular filtration rate (eGFR) and laboratory signs of thrombotic microangiopathy (TMA). Eight patients presented late (median 46 months, range 18-69 months) after transplantation. Of these, only 3 patients had systemic TMA, whereas 5 patients presented with slowly deteriorating eGFR without systemic TMA. Treatment with eculizumab resulted in improvement or stabilization of eGFR in 14 patients. Eculizumab discontinuation was tried in 7 patients; however, it was successful only in 3. At the end of the follow-up (median 29 months, range 3-54 months after start of eculizumab), 6 patients had eGFR <30 ml/min per 1.73 m². Graft loss had occurred in 3 of them. Overall, aHUS recurrence rate without eculizumab prophylaxis was 23%.

Conclusions

Rescue treatment of posttransplant aHUS recurrence is effective; however, some patients suffer from irreversible loss of kidney function, likely caused by delayed diagnosis and treatment and/or too aggressive discontinuation of eculizumab. Physicians should be aware that recurrence of aHUS can present without evidence of systemic TMA.

Kidney transplant in patients with atypical hemolytic uremic syndrome in the anti-C5 era: single-center experience with tailored Eculizumab

RATIONALE AND OBJECTIVE

Patients with atypical hemolytic uremic syndrome (aHUS) have long been considered ineligible for kidney transplantation (KTx) in several centers due to the high risk of disease recurrence, graft loss and life-threatening complications. The availability of Eculizumab (ECU) has now overcome this problem. However, the best approach towards timing, maintenance schedule, the possibility of discontinuation and patient monitoring has not yet been clearly established.

STUDY DESIGN

This is a single center case series presenting our experience with KTx in aHUS.

SETTING AND PARTICIPANTS

This study included 26 patients (16 females) with a diagnosis of aHUS, who spent a median of 5.5 years on kidney replacement therapy before undergoing KTx. We compared the aHUS relapse rate in three groups of patients who underwent KTx: patients who received no prophylaxis, patients who underwent plasma exchange, those who received Eculizumab prophylaxis. Complement factor H-related disease was by far the most frequent etiology (n = 19 patients).

RESULTS

Untreated patients and patients undergoing pre-KTx plasma exchange prophylaxis had a relapse rate of 0.81 (CI 0.30-1.76) and 3.1 (CI 0.64-9.16) events per 10 years cumulative observation, respectively, as opposed to 0 events among patients receiving Eculizumab prophylaxis. The time between Eculizumab doses was tailored based on classic complement pathway activity (target to < 30%). Using this strategy, 12 patients are currently receiving  Eculizumab every 28 days, 5 every 24-25 days, and 3 every 21 days.

CONCLUSION

Our experience supports the prophylactic use of Eculizumab in patients with a previous history of aHUS undergoing KTx, especially when complement dysregulation is well documented by molecular biology.

Optimal management of atypical hemolytic uremic disease: challenges and solutions

Atypical hemolytic uremic syndrome (aHUS) is a chronic life threatening condition that arises from genetic abnormalities resulting in uncontrolled complement amplifying activity. The introduction of eculizumab, the humanized monoclonal antibody, has brought about a paradigm shift in the management of aHUS. However, there are many knowledge gaps, diagnostic issues, access and cost issues, and patient or physician challenges associated with the use of this agent. Limited data on the natural history of aHUS along with the underlying genetic mutations make it difficult to predict the relapses and thereby raising concerns about the appropriate duration and monitoring of treatment. In this review, we discuss the safety and efficacy of eculizumab in patients with aHUS and its associated challenges.

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.

Treatment of thrombotic microangiopathy with a focus on new treatment options

The thrombotic microangiopathies (TMA) are a heterogeneous group of disorders, characterized by microangiopathic haemolytic anaemia with red cell fragmentation, thrombocytopenia and signs of organ dysfunction due to disturbed microcirculation. Current laboratory methods can be used to better distinguish some of these entities. Organ dysfunction can be severe and life-threatening, and immediate start of sufficient therapy is necessary to avoid permanent damage or death. The therapeutic options, however, are often limited to symptomatic measures, and are not standardized or based on high scientific evidence. During the preceding years, not only considerable progress has been made in better diagnosis of TMA, but also new therapeutic strategies have been established. Initial treatment still is based on plasma exchange and symptomatic measures to protect organ function. New concepts (immunosuppression, targeted anti-von Willebrand factor or anti-complement therapy, replacement with recombinant enzymes) are discussed in this article.

Influenza-associated thrombotic microangiopathies

Thrombotic microangiopathy (TMA) refers to phenotypically similar disorders, including hemolytic uremic syndromes (HUS) and thrombotic thrombocytopenic purpura (TTP). This review explores the role of the influenza virus as trigger of HUS or TTP. We conducted a literature survey in PubMed and Google Scholar using HUS, TTP, TMA, and influenza as keywords, and extracted and analyzed reported epidemiological and clinical data. We identified 25 cases of influenza-associated TMA. Five additional cases were linked to influenza vaccination and analyzed separately. Influenza A was found in 83%, 10 out of 25 during the 2009 A(H1N1) pandemic. Two patients had bona fide TTP with ADAMTS13 activity <10%. Median age was 15 years (range 0.5-68 years), two thirds were male. Oligoanuria was documented in 81% and neurological involvement in 40% of patients. Serum C3 was reduced in 5 out of 14 patients (36%); Coombs test was negative in 7 out of 7 and elevated fibrin/fibrinogen degradation products were documented in 6 out of 8 patients. Pathogenic complement gene mutations were found in 7 out of 8 patients tested (C3, MCP, or MCP combined with CFB or clusterin). Twenty out of 24 patients recovered completely, but 3 died (12%). Ten of the surviving patients underwent plasma exchange (PLEX) therapy, 5 plasma infusions. Influenza-mediated HUS or TTP is rare. A sizable proportion of tested patients demonstrated mutations associated with alternative pathway of complement dysregulation that was uncovered by this infection. Further research is warranted targeting the roles of viral neuraminidase, enhanced virus-induced complement activation and/or ADAMTS13 antibodies, and rational treatment approaches.

Clinical Relapses of Atypical HUS on Eculizumab: Clinical Gap for Monitoring and Individualised Therapy

Atypical hemolytic uremic syndrome (aHUS) is caused by dysregulation of the complement system. A humanised anti-C5 monoclonal antibody (eculizumab) is available for the treatment of aHUS. We present the first description of atypical HUS in a child with a coexistent diagnosis of a POL-III leukodystrophy. On standard eculizumab dosing regime, there was evidence of ongoing C5 cleavage and clinical relapses when immunologically challenged. Eculizumab is an effective therapy for aHUS, but the recommended doses may not be adequate for all patients, highlighting the need for ongoing efforts to develop a strategy for monitoring of treatment efficacy and potential individualisation of therapy.

Complement activation in patients with isolated antiphospholipid antibodies or primary antiphospholipid syndrome

The antiphospholipid syndrome (APS) is the association of thrombosis and recurrent pregnancy loss and/or pregnancy morbidity with persistent antiphospholipid antibodies (aPL). Increased complement activation has been implicated in the pathogenesis of APS in animal models. It was our objective to evaluate complement activation in patients with aPL or primary antiphospholipid syndrome (PAPS). We measured complement activation products, fragments Bb and C3a–desArg by ELISA in 186 aPL/PAPS patients and 30 healthy controls. All patients with aPL had significantly increased levels of complement activation products. Fragment Bb levels (mean, 95% CI); (thrombotic APS 0.54 units/ml, 0.31–0.83, obstetric APS 0.60 units/ml,0.39–1.02, isolated aPL 0.48 units/ml, 0.29–0.85, overall 0.39 units/ml, 0.33–0.47) and C3a–desArg levels (mean, 95% CI): (thrombotic APS 261 ng/ml, 219–311, obstetric APS 308 ng/ml, 243–391, isolated aPL 258 ng/ml, 193–337, overall 225 ng/ml, 202–251) were significantly higher compared to controls (fragment Bb 0.06 units/ml, 0.03–0.11, C3a–desArg 69 ng/ml, 50–92). There were correlations between Fragment Bb and C3a–desArg levels in all patients with aPL. Receiver operator characteristic (ROC) analysis showed increased fragment Bb and C3a–desArg levels had strong associations with the presence of persistent lupus anticoagulant (area under ROC: Bb 0.89, and C3a–desArg 0.90), dual and triple aPL positivity (Bb 0.71–0.82, C3a–desArg 0.71–0.80) but not with high titre anti-cardiolipin antibodies (Bb 0.62, C3a–desArg 0.65), or anti β2-glycoprotein 1 antibodies (Bb 0.66, C3a–desArg 0.67). Complement activation is present in all patient groups within this large cohort of patients aPL. This suggests it may have a major role in the pathogenesis of APS and merits further study.

Occurrence of atypical HUS associated with influenza B

Hemolytic uremic syndrome (HUS) is a disease characterized by thrombotic microangiopathy with a triad of non-immune hemolytic anemia, thrombocytopenia, and renal impairment. Approximately 10% of cases of HUS are classified as atypical (aHUS). While today many genetically forms of aHUS pathology are known, only about 50% of carriers precipitate the disease. The reason remains unclear, and triggering events like intercurrent infections have been postulated. In rare cases, influenza A is the known trigger of aHUS; however, no cases of influenza B have been reported.

CONCLUSION

We describe for the first time that influenza B strain as a trigger for aHUS in children with primary hereditary forms. We also showed in our three cases that immunization appears to be safe; however, this needs to be confirmed in a larger cohort. What is Known: • Known triggers of aHUS are infectious specimen. • Influenza A-associated aHUS cases are rarely published. What is New: • aHUS can be triggered by influenza B virus infection. • Influenza vaccination of patients with aHUS appears safe.

A case of atypical hemolytic uremic syndrome in a second renal transplant

Atypical hemolytic uremic syndrome (aHUS) has gained increased visibility over several years as an important cause of renal failure. Unfortunately, diagnosis is often difficult because individual courses can be highly variable depending the causative genetic mutations. Here we present the case of a patient with a failed renal allograft and acute failure of a second allograft who was ultimately diagnosed with aHUS. Interestingly, he developed early de novo donor specific antibodies (DSA) after the second renal transplant in context of likely recurrent aHUS. Terminal complement inhibition with eculizumab resulted in prompt improvement of renal allograft function.

Atypical hemolytic uremic syndrome in the setting of complement-amplifying conditions: case reports and a review of the evidence for treatment with eculizumab

Atypical hemolytic uremic syndrome (aHUS) is a rare, genetic, progressive, life-threatening form of thrombotic microangiopathy (TMA) predominantly caused by dysregulation of the alternative pathway of the complement system. Complement-amplifying conditions (CACs), including pregnancy complications [preeclampsia, HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome], malignant hypertension, autoimmune diseases, transplantation, and others, are associated with the onset of TMA in up to 69 % of cases of aHUS. CACs activate the alternative pathway of complement and may be comorbid with aHUS or may unmask a previously undiagnosed case. In this review, three case reports are presented illustrating the onset and diagnosis of aHUS in the setting of different CACs (pregnancy complications, malignant hypertension, renal transplantation). The report also reviews the evidence for a variety of CACs, including those mentioned above as well as infections and drug-induced TMA, and the overlap with aHUS. Finally, we introduce an algorithm for diagnosis and treatment of aHUS in the setting of CACs. If TMA persists despite initial management for the specific CAC, aHUS should be considered. The terminal complement inhibitor eculizumab should be initiated for all patients with confirmed diagnosis of aHUS, with or without a comorbid CAC.

Atypical hemolytic uremic syndrome: a clinical conundrum

BACKGROUND

Patients negative for Shiga toxin-producing E. coli (STEC) are categorized as having atypical hemolytic uremic syndrome (HUS) and are associated with an increased risk for complement mutations and poorer prognosis compared with typical HUS. However, STEC identification is limited by the natural history of HUS.

METHODS

The current study is aimed at identifying HUS patients with poor outcomes based on the presence or absence of diarrhea (D) or Shiga toxin (S). A single-center retrospective review (2003-2012) of 42 HUS patients (follow-up 31.3 ± 38.7 months) was carried out. HUS was managed clinically with supportive treatments such as dialysis, plasma therapy, and eculizumab.

RESULTS

There was no significant difference in the D+S+ (31 %), D+S- (50 %) and D-S- (19 %) groups in the outcome variables of chronic kidney disease stages I-II (100 % vs 81 % vs 67 %) and proteinuria at follow-up (20 % vs 12.5 % vs 33.3 %), hospitalization duration (16.0 ± 8.7 vs 18.1 ± 9.5 vs 23.7 ± 12.9 days); dialysis requirement (50 % vs 81 % vs 66.7 %), and dialysis duration (10.2 ± 1.9 vs 33.3 ± 72.8 vs 10.3 ± 8.1 days). There was no significant difference in study outcomes in STEC+ (59 %) versus STEC- (41 %) groups. Genetic testing was performed in 12 % of HUS patients based on age, recurrent HUS, familial HUS, persistently low C3, or prolonged dialysis, and 80 % of the patients tested were positive for genetic mutations.

CONCLUSIONS

Our study does not show poorer outcomes in STEC- HUS. Indications and the cost-effectiveness of genetic testing, eculizumab, and plasmapheresis in STEC- HUS need to be evaluated further.

Postinfectious Hemolytic Uremic Syndrome

Post-infectious hemolytic uremic syndrome (HUS) is caused by specific pathogens in patients with no identifiable HUS-associated genetic mutation or autoantibody. The majority of episodes is due to infections by Shiga toxin (Stx) producing Escherichia coli (STEC). This chapter reviews the epidemiology and pathogenesis of STEC-HUS, including bacterial-derived factors and host responses. STEC disease is characterized by hematological (microangiopathic hemolytic anemia), renal (acute kidney injury) and extrarenal organ involvement. Clinicians should always strive for an etiological diagnosis through the microbiological or molecular identification of Stx-producing bacteria and Stx or, if negative, serological assays. Treatment of STEC-HUS is supportive; more investigations are needed to evaluate the efficacy of putative preventive and therapeutic measures, such as non-phage-inducing antibiotics, volume expansion and anti-complement agents. The outcome of STEC-HUS is generally favorable, but chronic kidney disease, permanent extrarenal, mainly cerebral complication and death (in less than 5 %) occur and long-term follow-up is recommended. The remainder of this chapter highlights rarer forms of (post-infectious) HUS due to S. dysenteriae, S. pneumoniae, influenza A and HIV and discusses potential interactions between these pathogens and the complement system.

Complement-here, there and everywhere, but what about the transplanted organ?

The part of the innate immune system that communicates and effectively primes the adaptive immune system was termed "complement" by Ehrlich to reflect its complementarity to antibodies having previously been described as "alexine" (i.e protective component of serum) by Buchner and Bordet. It has been established that complement is not solely produced systemically but may have origin in different tissues where it can influence organ specific functions that may affect the outcome of transplanted organs. This review looks at the role of complement in particular to kidney transplantation. We look at current literature to determine whether blockade of the peripheral or central compartments of complement production may prevent ischaemic reperfusion injury or rejection in the transplanted organ. We also review new therapeutics that have been developed to inhibit components of the complement cascade with varying degrees of success leading to an increase in our understanding of the multiple triggers of this complex system. In addition, we consider whether biomarkers in this field are effective markers of disease or treatment.

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.

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.

Arterial hypertension in children with hemolytic uremic syndrome after kidney transplantation

The development of arterial hypertension after KTX is a well-known complication. HUS is a systemic disease associated with arterial hypertension during long-term follow-up. Our goal was to report on the severity of arterial hypertension after KTX in patients with typical and atypical HUS. We analyzed the course of 197 patients with HUS, of which 22 (n = 10 with typical HUS; n = 12 with atypical HUS) developed ESRF and received KTX as renal replacement therapy. We analyzed data from 1766 casual BP and 85 24-h ABPM measurements. In addition, we evaluated the used antihypertensive strategy. Comparison between the two patient groups revealed that patients with atypical HUS had significantly higher casual SBP-SDS and DBP-SDS values after KTX despite similar intensity of antihypertensive treatment. These data were supported by analysis of ABPM profiles showing comparable results for the interval 1-5 yr after KTX. Patients with atypical HUS had a greater severity of arterial hypertension despite similar treatment strategies and intensity of treatment. Our observation, even though in a small cohort, supports recent genetic studies showing arterial hypertension closely associated with HUS-causing mutations in patients with atypical HUS.

Primary disease recurrence—effects on paediatric renal transplantation outcomes

Primary disease recurrence after renal transplantation is mainly diagnosed by examination of biopsy samples, but can also be associated with clinical symptoms. In some patients, recurrence can lead to graft loss (7-8% of all graft losses). Primary disease recurrence is generally associated with a high risk of graft loss in patients with focal segmental glomerulosclerosis, membranous proliferative glomerulonephritis, primary hyperoxaluria or atypical haemolytic uraemic syndrome. By contrast, disease recurrence is associated with a limited risk of graft loss in patients with IgA nephropathy, renal involvement associated with Henoch-Schönlein purpura, antineutrophil cytoplasmic antibody-associated glomerulonephritis or lupus nephritis. The presence of systemic diseases that affect the kidneys, such as sickle cell anaemia and diabetes mellitus, also increases the risk of delayed graft loss. This Review provides an overview of the epidemiology, pathophysiology and management of primary disease recurrence in paediatric renal graft recipients, and describes the overall effect on graft survival of each of the primary diseases listed above. With appropriate management, few paediatric patients should be excluded from renal transplantation programmes because of an increased risk of recurrence.

Eculizumab to treat antibody-mediated rejection in a 7-year-old kidney transplant recipient

We report on successful early eculizumab administration to treat acute antibody-mediated rejection (ABMR) in a highly sensitized kidney transplant recipient. The recipient is a 7-year-old boy who received, 6 months after a desensitization protocol with monthly intravenous immunoglobulin infusion, a second kidney transplant in the presence of low donor-specific antibodies (DSAs). Both pretransplant lymphocytotoxic and flow cytometric crossmatch were negative. Allograft function recovered promptly, with excellent initial function. On postoperative day (POD) 4, the child developed significant proteinuria with an acute rise in serum creatinine. Allograft biopsy showed severe acute ABMR. Intravenous eculizumab (600 mg), preceded by a single session of plasmapheresis, was administered on POD 5 and 12 along with a 4-day thymoglobulin course. After the first dose of eculizumab, a strikingly rapid normalization of allograft function with a decrease in proteinuria occurred. However, because circulating DSA levels remained elevated, the child received 3 doses of intravenous immunoglobulin (POD 15, 16, and 17), with a significant subsequent decrease in DSA levels. At 9 months after transplant, the child continues to maintain excellent allograft function with undetectable circulating DSA levels. This unique case highlights the potential efficacy of using early eculizumab to rapidly reverse severe ABMR in pediatric transplantation, and therefore it suggests a novel therapeutic approach to treat acute ABMR.

Mapping interactions between complement C3 and regulators using mutations in atypical hemolytic uremic syndrome

The pathogenesis of atypical hemolytic uremic syndrome (aHUS) is strongly linked to dysregulation of the alternative pathway of the complement system. Mutations in complement genes have been identified in about two-thirds of cases, with 5% to 15% being in C3. In this study, 23 aHUS-associated genetic changes in C3 were characterized relative to their interaction with the control proteins factor H (FH), membrane cofactor protein (MCP; CD46), and complement receptor 1 (CR1; CD35). In surface plasmon resonance experiments, 17 mutant recombinant proteins demonstrated a defect in binding to FH and/or MCP, whereas 2 demonstrated reduced binding to CR1. In the majority of cases, decreased binding affinity translated to a decrease in proteolytic inactivation (known as cofactor activity) of C3b via FH and MCP. These results were used to map the putative binding regions of C3b involved in the interaction with MCP and CR1 and interrogated relative to known FH binding sites. Seventy-six percent of patients with C3 mutations had low C3 levels that correlated with disease severity. This study expands our knowledge of the functional consequences of aHUS-associated C3 mutations relative to the interaction of C3 with complement regulatory proteins mediating cofactor activity.

Atypical hemolytic uremic syndrome post-kidney transplantation: two case reports and review of the literature

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder characterized by over-activation and dysregulation of the alternative complement pathway. Its estimated prevalence is 1–2 per million. The disease is characterized by thrombotic microangiopathy, which causes anemia, thrombocytopenia, and acute renal failure. aHUS has more severe course compared to typical (infection-induced) HUS and is frequently characterized by relapses that leads to end stage renal disease. For a long time, kidney transplantation for these patients was contraindicated because of high rate of recurrence and subsequent renal graft loss. The post-kidney transplantation recurrence rate largely depends on the pathogenetic mechanisms involved. However, over the past several years, advancements in the understanding and therapeutics of aHUS have allowed successful kidney transplantation in these patients. Eculizumab, which is a complement C5 antibody that inhibits complement factor 5a and subsequent formation of the membrane-attack complex, has been used in prevention and treatment of post-transplant aHUS recurrence. In this paper, we present two new cases of aHUS patients who underwent successful kidney transplantation in our center with the use of prophylactic and maintenance eculizumab therapy that have not been published before. The purpose of reporting these two cases is to emphasize the importance of using eculizumab as a prophylactic therapy to prevent aHUS recurrence post-transplant in high-risk patients. We will also review the current understanding of the genetics of aHUS, the pathogenesis of its recurrence after kidney transplantation, and strategies for prevention and treatment of post-transplant aHUS recurrence.

New functional and structural insights from updated mutational databases for complement factor H, Factor I, membrane cofactor protein and C3

aHUS (atypical haemolytic uraemic syndrome), AMD (age-related macular degeneration) and other diseases are associated with defective AP (alternative pathway) regulation. CFH (complement factor H), CFI (complement factor I), MCP (membrane cofactor protein) and C3 exhibited the most disease-associated genetic alterations in the AP. Our interactive structural database for these was updated with a total of 324 genetic alterations. A consensus structure for the SCR (short complement regulator) domain showed that the majority (37%) of SCR mutations occurred at its hypervariable loop and its four conserved Cys residues. Mapping 113 missense mutations onto the CFH structure showed that over half occurred in the C-terminal domains SCR-15 to -20. In particular, SCR-20 with the highest total of affected residues is associated with binding to C3d and heparin-like oligosaccharides. No clustering of 49 missense mutations in CFI was seen. In MCP, SCR-3 was the most affected by 23 missense mutations. In C3, the neighbouring thioester and MG (macroglobulin) domains exhibited most of 47 missense mutations. The mutations in the regulators CFH, CFI and MCP involve loss-of-function, whereas those for C3 involve gain-of-function. This combined update emphasizes the importance of the complement AP in inflammatory disease, clarifies the functionally important regions in these proteins, and will facilitate diagnosis and therapy.

A new compilation of 324 mutations in four major proteins from the complement alternative pathway reveals mutational hotspots in factor H and complement C3, and less so in factor I and membrane cofactor protein. Their associations with function are discussed.

Atypical Hemolytic Uremic Syndrome: Differential Diagnosis from TTP/HUS and Management

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA). It has an unfavorable outcome with death rates as high as 25% during the acute phase and up to 50% of cases progressing to end-stage renal failure. Uncontrolled complement activation through the alternative pathway is thought to be the main underlying pathopysiology of aHUS and corresponds to all the deleterious findings of the disease. Thrombotic thrombocytopenic purpura (TTP) and Shiga toxin-associated HUS are the 2 other important TMA diseases. Although differentiating HUS from TTP is relatively easy in children with a preceding diarrheal illness or invasive S. pneumoniae, differentiating aHUS from TTP or other microangiopathic disorders can present a major diagnostic challenge in adults. ADAMTS13 analysis is currently the most informative diagnostic test for differentiating TTP, congenital TTP, and aHUS. Today empiric plasma therapy still is recommended by expert opinion to be used as early as possible in any patient with symptoms of aHUS. The overall treatment goal remains restoration of a physiological balance between activation and control of the alternative complement pathway. So it is a reasonable approach to block the terminal complement complex with eculizumab in order to prevent further organ injury and increase the likelihood organ recovery. Persistence of hemolysis or lack of improvement of renal function after 3-5 daily plasmaphereses have to be regarded as the major criteria for uncontrolled TMA even if platelet count has normalized and as an indication to switch the treatment to eculizumab. Eculizumab has changed the future perspectives of patients with aHUS and both the FDA and the EMA have approved it as life-long treatment. However, there are still some unresolved issues about the follow-up such as the optimal duration of eculizumab treatment and whether it can be stopped or how to stop the therapy.

Prophylactic eculizumab for kidney transplantation in a child with atypical hemolytic uremic syndrome due to complement factor H mutation

We present a case of successful deceased-donor kidney transplantation in a three-yr-old child with aHUS due to complement factor H mutation, using only prophylactic eculizumab treatment prior to transplant. She developed disease exacerbation in the immediate post-operative period despite having therapeutic eculizumab concentrations and evidence for complete complement pathway blockade. The patient responded well to additional doses of eculizumab and has maintained excellent graft function and disease control in the first year post-transplantation. The optimal dosing scheme for eculizumab in the perioperative period remains to be determined. More sensitive biomarkers of early disease activity are needed to improve disease monitoring. Finally, the duration of eculizumab therapy in patients with aHUS remains to be determined.

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.

Managing and preventing atypical hemolytic uremic syndrome recurrence after kidney transplantation

PURPOSE OF REVIEW

Several genetic and acquired abnormalities leading to abnormal activation of the alternative pathway of complement have been identified in patients with atypical hemolytic uremic syndrome (aHUS). The purpose of this review is to shed light on how advances in the understanding of aHUS pathogenesis have impacted on prevention and cure of aHUS recurrence after kidney transplantation.

RECENT FINDINGS

Studies over the past decade have shown that the risk of posttransplant recurrence of aHUS depends on the underlying genetic abnormality. The risk is high in patients with mutations in genes encoding circulating complement proteins and regulators, whereas patients with mutations in membrane cofactor protein generally show good transplant outcome. Given the poor outcome associated with recurrence, isolated renal transplantation had been contraindicated in aHUS patients. Combined kidney-liver transplantation and prophylactic plasma exchange have been used to prevent posttransplant recurrences. More recent data have provided evidence about the efficacy of the anti-C5 monoclonal antibody eculizumab in the prevention and treatment of posttransplant aHUS recurrences.

SUMMARY

This review summarizes recent advances on preventing and managing aHUS recurrence after kidney transplantation and discusses the issues that still need clarification.

Current treatment of atypical hemolytic uremic syndrome

Tremendous advances have been made in understanding the pathogenesis of atypical Hemolytic Uremic Syndrome (aHUS), an extremely rare disease. Insights into the molecular biology of aHUS resulted in rapid advances in treatment with eculizumab (Soliris(®), Alexion Pharmaceuticals Inc.). Historically, aHUS was associated with very high rates of mortality and morbidity. Prior therapies included plasma therapy and/or liver transplantation. Although often life saving, these were imperfect and had many complications. We review the conditions included under the rubric of aHUS: S. pneumoniae HUS (SpHUS), inborn errors of metabolism, and disorders of complement regulation, emphasizing their differences and similarities. We focus on the clinical features, diagnosis, and pathogenesis, and treatment of aHUS that results from mutations in genes encoding alternative complement regulators, SpHUS and HUS associated with inborn errors of metabolism. Mutations in complement genes, or antibodies to their protein products, result in unregulated activity of the alternate complement pathway, endothelial injury, and thrombotic microangiopathy (TMA). Eculizumab is a humanized monoclonal antibody that inhibits the production of the terminal complement components C5a and the membrane attack complex (C5b-9) by binding to complement protein C5a. This blocks the proinflammatory and cytolytic effects of terminal complement activation. Eculizumab use has been reported in many case reports, and retrospective and prospective clinical trials in aHUS. There have been few serious side effects and no reports of tachphylaxis or drug resistance. The results are very encouraging and eculizumab is now recognized as the treatment of choice for aHUS.

Successful treatment of DEAP-HUS with eculizumab

BACKGROUND

Deficiency of complement factor H-related (CFHR) proteins and CFH autoantibody-positive hemolytic uremic syndrome (DEAP-HUS) represents a unique subgroup of complement-mediated atypical HUS (aHUS). Autoantibodies to the C-terminus of CFH block CFH surface recognition and mimic mutations found in the genetic form of (CFH-mediated) aHUS. CFH autoantibodies are found in 10-15 % of aHUS patients and occur--so far unexplained--almost exclusively in the background of CFHR1 or CFHR3/CFHR1 deletions.

METHODS

As a well-defined role for eculizumab in the treatment of complement-mediated aHUS is becoming established, its role in DEAP-HUS is less conspicuous, where a B-cell-depleting and immunosuppressive treatment strategy is being proposed in the literature.

RESULTS

We here show eculizumab to be safe and effective in maintaining a disease-free state, without recurrence, in a previously plasma-therapy-dependent DEAP-HUS patient, and in another patient in whom, although showing a good clinical response to plasma therapy, the therapy was hampered by allergic reactions to fresh frozen plasma and contend there is a rationale for the use of eculizumab in concert with an immunosuppressive strategy in the treatment of DEAP-HUS. Considering the high rate of early relapse, the possible coexistence and contribution of both known and unknown complement-gene mutations, the probable pathogenic role of CFHR1 as a complement alternative pathway (CAP) regulator, the experimental nature of measuring and using anti-CFH autoantibodies to guide management, and until the positive reports of immunosuppression in addition to plasma therapy are confirmed in prospective studies, we feel that a complement-directed therapy should not be neglected in DEAP-HUS. Serial CFH autoantibody titer testing may become a valuable tool to monitor treatment response, and weaning patients off eculizumab may become an option once CFH autoantibody levels are depleted.

CONCLUSIONS

A prospective study of eculizumab treatment in a larger cohort of DEAP-HUS patients is required to validate the applicability of our positive experience.

Hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy defined by thrombocytopenia, nonimmune microangiopathic hemolytic anemia, and acute renal failure. The most frequent form is associated with infections by Shiga-like toxin-producing bacteria (STEC-HUS). Rarer cases are triggered by neuraminidase-producing Streptococcus pneumoniae (pneumococcal-HUS). The designation of aHUS is used to refer to those cases in which an infection by Shiga-like toxin-producing bacteria or S. pneumoniae can be excluded. Studies performed in the last two decades have documented that hyperactivation of the complement system is the pathogenetic effector mechanism leading to the endothelial damage and the microvascular thrombosis in aHUS. Recent data suggested the involvement of the complement system in the pathogenesis of STEC-HUS and pneumococcal-HUS as well. Clinical signs and symptoms may overlap among the different forms of HUS; however, pneumococcal-HUS and aHUS have a worse prognosis compared with STEC-HUS. Early diagnosis and identification of underlying pathogenetic mechanism allows instating specific support measures and therapies. In clinical trials in patients with aHUS, complement inhibition by eculizumab administration leads to a rapid and sustained normalization of hematological parameters with improvement in long-term renal function. This review summarizes current concepts about the epidemiological findings, the pathological and clinical aspects of STEC-HUS, pneumococcal-HUS, and aHUS, and their diagnosis and management.

New immunosuppressive agents in pediatric transplantation

Immunosuppressive therapy in pediatrics continues to evolve. Over the past decade, newer immunosuppressive agents have been introduced into adult and pediatric transplant patients with the goal of improving patient and allograft survival. Unfortunately, large-scale randomized clinical trials are not commonly performed in children. The purpose of this review is to discuss the newer immunosuppressive agents available for induction therapy, maintenance immunosuppression, and the treatment of rejection.

Novel immunosuppressive agents in kidney transplantation

Excellent outcomes have been achieved in the field of renal transplantation. A significant reduction in acute rejection has been attained at many renal transplant centers using contemporary immunosuppressive, consisting of an induction agent, a calcineurin inhibitor, an antiproliferative agent plus or minus a corticosteroid. Despite improvements with these regimens, chronic allograft injury and adverse events still persist. The perfect immunosuppressive regimen would limit or eliminate calcineurin inhibitors and/or corticosteroid toxicity while providing enhanced allograft outcomes. Potential improvements to the calcineurin inhibitor class include a prolonged release tacrolimus formulation and voclosporin, a cyclosporine analog. Belatacept has shown promise as an agent to replace calcineurin inhibitors. A novel, fully-human anti-CD40 monoclonal antibody, ASKP1240, is currently enrolling patients in phase 2 trials with calcineurin minimization and avoidance regimens. Another future goal of transplant immunosuppression is effective and safe treatment of allograft rejection. Novel treatments for antibody mediated rejection include bortezomib and eculizumab. Several investigational agents are no longer being pursed in transplantation including the induction agents, efalizumab and alefacept, and maintenance agents, sotrastaurin and tofacitinib. The purpose of this review is to consolidate the published evidence of the effectiveness and safety of investigational immunosuppressive agents in renal transplant recipients.

Targeted strategies in the prevention and management of atypical HUS recurrence after kidney transplantation

Atypical hemolytic and uremic syndrome (aHUS) is associated with a high rate of recurrence and poor outcomes after kidney transplantation. Fortunately, recent advances in the understanding of the pathogenesis of aHUS have permitted an individualized risk assessment of post-transplant recurrence. Acquired or inherited dysregulation of the alternative complement pathway, thought to be the driving force of the disease, is identified in most aHUS patients. Notably, depending on the mutations involved, the risk of recurrence greatly varies, highlighting the importance of undertaking etiological investigations prior to kidney transplantation. In those with moderate to high risk of recurrence, the use of a prophylactic therapy, consisting in either plasmapheresis or eculizumab therapies, represents a major stride forward in the prevention of aHUS recurrence after kidney transplantation. In those who experience aHUS recurrence, a growing number of observations suggest that eculizumab therapy outperforms curative plasma therapy. The optimal duration of both prophylactic and curative therapies remains an important, yet unaddressed, issue. In this respect, the kidney transplant recipients, continuously exposed to endothelial-insulting factors, referred here as to triggers, might have a sustained high risk of recurrence. A global therapeutic approach should thus attempt to reduce exposure to these triggers.

Eculizumab therapy for atypical haemolytic uraemic syndrome due to a gain-of-function mutation of complement factor B

BACKGROUND

Atypical haemolytic uraemic syndrome (aHUS) is caused by dysregulated complement activation. A humanised anti-C5 monoclonal antibody has recently become available for treatment of this condition

CASE-DIAGNOSIS/TREATMENT

We present the first description of an infant with an activating mutation of complement factor B successfully treated with eculizumab. On standard doses she had evidence of ongoing C5 cleavage despite a good clinical response.

CONCLUSIONS

Eculizumab is effective therapy for aHUS associated with factor B mutations, but recommended doses may not be adequate for all patients.

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.

Tailored eculizumab therapy in the management of complement factor H-mediated atypical hemolytic uremic syndrome in an adult kidney transplant recipient: a case report

Atypical hemolytic uremic syndrome (aHUS) is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury (AKI) which frequently progresses to end-stage renal disease (ESRD). In 50% of affected patients, mutations in complement regulatory proteins cause inappropriate complement activation with endothelial injury. Complement factor H (CFH) mutations cause 25% of aHUS cases; these patients have an 80% recurrence risk after kidney transplantation. Eculizumab, an anti-C5 antibody, is effective in limiting hemolysis episodes in patients with aHUS, but less is known about preventing recurrence after kidney transplantation. Herein we report the use of prophylactic eculizumab in an adult with aHUS who underwent kidney transplantation. A 31-year-old female presented with aHUS and progressive AKI associated with low complement 3 level leading to ESRD despite plasmapheresis and corticosteroids. She had a heterozygous nonsense mutation in CFH and reduced plasma CFH levels. She was given preoperative plasmapheresis and eculizumab and underwent living unrelated renal transplantation. Postoperatively, eculizumab was dosed to achieve low functional complement 5 levels and low soluble membrane attack complex levels and she has maintained excellent graft function without aHUS recurrence. We propose that eculizumab with titrated dosing should be used in CFH-mediated aHUS patients who are at a high risk of recurrence.

Changing strategies for organ transplantation in atypical haemolytic uraemic syndrome: a tertiary case series

We present three cases of organ transplantation for atypical haemolytic uraemic syndrome secondary to complement factor H mutation: one isolated renal transplant; one previously reported isolated liver transplant; and one combined liver and kidney transplant. All three patients were treated prior to the licensing of eculizumab for this condition, and all have had favourable outcomes with maintenance of graft function for years following transplantation. We discuss the evolution of transplantation therapy for aHUS over the last two decades. Transplantation decision-making in aHUS has evolved over this time with expanding knowledge of pathophysiology and genetics, alongside refined plasma exchange and anticoagulation protocols and improved centre experience. Our cases demonstrate how individual patient factors within this heterogeneous condition also underlie transplantation decisions and outcomes. Whilst our cases demonstrate that transplantation in aHUS can be a successful long-term treatment providing good quality of life, worldwide experience has proven that most curative treatment for aHUS strategies represents significant risks. Whether new pharmacotherapies such as eculizumab will alter this risk is yet to be determined.

Complement disorders and hemolytic uremic syndrome

PURPOSE OF REVIEW

Complement mediated hemolytic uremic syndrome (aHUS) accounts for a significant proportion of non-shiga toxin HUS. The purpose of this review is to outline the pathophysiology, clinical features and therapeutic options for aHUS.

RECENT FINDINGS

In the last decade, strides have been made in identifying several new disease-causing mutations in complement-regulating proteins.

SUMMARY

Complement mediated HUS (aHUS) has a worse prognosis compared with shiga toxin mediated HUS, often resulting in end stage renal disease. Early identification of aHUS is crucial so that plasma therapy can be initiated. After renal transplantation, there is very high risk of disease recurrence and graft loss. Eculizumab and combined liver-kidney transplantation offer promise for improved prognosis.

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.

Combined complement gene mutations in atypical hemolytic uremic syndrome influence clinical phenotype

Several abnormalities in complement genes reportedly contribute to atypical hemolytic uremic syndrome (aHUS), but incomplete penetrance suggests that additional factors are necessary for the disease to manifest. Here, we sought to describe genotype-phenotype correlations among patients with combined mutations, defined as mutations in more than one complement gene. We screened 795 patients with aHUS and identified single mutations in 41% and combined mutations in 3%. Only 8%-10% of patients with mutations in CFH, C3, or CFB had combined mutations, whereas approximately 25% of patients with mutations in MCP or CFI had combined mutations. The concomitant presence of CFH and MCP risk haplotypes significantly increased disease penetrance in combined mutated carriers, with 73% penetrance among carriers with two risk haplotypes compared with 36% penetrance among carriers with zero or one risk haplotype. Among patients with CFH or CFI mutations, the presence of mutations in other genes did not modify prognosis; in contrast, 50% of patients with combined MCP mutation developed end stage renal failure within 3 years from onset compared with 19% of patients with an isolated MCP mutation. Patients with combined mutations achieved remission with plasma treatment similar to patients with single mutations. Kidney transplant outcomes were worse, however, for patients with combined MCP mutation compared with an isolated MCP mutation. In summary, these data suggest that genotyping for the risk haplotypes in CFH and MCP may help predict the risk of developing aHUS in unaffected carriers of mutations. Furthermore, screening patients with aHUS for all known disease-associated genes may inform decisions about kidney transplantation.