Long-term remission of atypical HUS with anti-factor H antibodies after cyclophosphamide pulses

New findings in preventing recurrence and improving renal function in AHUS patients after renal transplantation treated with eculizumab: a systemic review and meta-analyses

BACKGROUND

The long-term mortality of kidney transplantation patients with atypical hemolytic uremic syndrome remains high, and the efficacy of the main treatment eculizumab is still controversial.

OBJECTIVE

A comprehensive systematic review and meta-analysis of clinical trials using eculizumab in renal transplant patients with atypical hemolytic uremic syndrome was conducted to evaluate the efficacy of this therapy and its impact on renal function.

METHODS

A comprehensive systematic search was conducted across multiple reputable databases, including Ovid (MEDLINE, EMBASE), PubMed, and the Cochrane Library (since database inception), to identify relevant studies exploring the use of eculizumab in patients with atypical hemolytic uremic kidney transplantation. Various renal function parameters, such as dialysis, rejection, glomerular filtration rate, serum creatinine, lactate dehydrogenase, and platelet count, along with patient relapse rates, were extracted and summarized using a combination of robust statistical methods, including fixed effects, random effects, and general inverse variance methods.

RESULT

Eighteen trials with 618 subjects were analyzed. Our analysis suggests that the use of eculizumab is associated with a reduced likelihood of AHUS recurrence (odds ratio (OR) = 0.05, 95% CI: 0.00-0.13), as well as a significant reduction in the need for dialysis (odds ratio (OR) = 0.13, 95% CI: 0.01-0.32). Additionally, eculizumab treatment led to lower serum creatinine levels (mean differences (MD) = 126.931μmoI/L, 95% CI: 115.572μmoI/L-138.290μmoI/L) and an improved glomerular filtration rate (mean differences (MD) = 59.571 ml/min, 95% CI: 57.876 ml/min-61.266 mL/min). Our results also indicate that the use of eculizumab reduces the likelihood of rejection (odds ratio (OR) = 0.09, 95% CI: 0.01-0.22). Furthermore, the drug was effective in improving platelet counts (×10∧9/L) (mean differences (MD) = 163.421, 95% CI: 46.998-279.844) and lactate dehydrogenase levels (mean differences (MD) = 336.608 U/L, 95% CI: 164.816 U/L-508.399 U/L).

CONCLUSIONS

Based on the meta-analysis, treatment with eculizumab can reduce dialysis rates and improve patients' quality of life by enhancing renal function.

Immunosuppressive Therapy of Antibody-Mediated aHUS and TTP

The recent classification of pediatric thrombotic microangiopathies (TMA) takes into consideration mechanisms of disease for guidance to targeted therapies. We present our experience with seven patients with antibody mediated atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP). Five children had aHUS with antibodies against complement factor H (CFH-ab) and two with TTP with antibodies against metalloproteinase ADAMTS13. In the aHUS cases diagnosed and treated before the eculizumab era, CFH-ab was detected using the ELISA assay. Mutational analysis of selected complement genes was performed. TTP was diagnosed if, in addition to microangiopathic hemolytic anemia and thrombocytopenia, ischemic organ involvement and severe deficiency in ADAMTS13 activity were present. Treatment protocol consisted of plasma exchanges (PE) and steroid pulses, followed by the combination of cyclophosphamide and rituximab to achieve long-term immunosuppression. Four patients with CFH-ab and the TTP patients with ADAMTS13 antibodies came into sustained remission. After a median follow-up of 11.7 (range 7.7-12.9) years without maintenance therapy, no disease recurrence was observed; nevertheless, six patients, two had hypertension and two had proteinuria as a late consequence. One patient, with late diagnosis of CFH-ab and additional genetic risk factors who was treated only with PE and plasma substitution, reached end-stage renal disease and was later successfully transplanted using eculizumab prophylaxis. In the cases of antibody-mediated TMAs, PE and early immunosuppressive treatment may result in sustained remission with preserved kidney function. Further data are needed to establish optimal treatment of anti-FH antibody-associated HUS.

Case report: Eculizumab plus obinutuzumab induction in a deceased donor kidney transplant recipient with DEAP-HUS

The wide-spread use of the anti-complement component 5 monoclonal antibody (moAb) eculizumab has greatly reduced the incidence of relapsing atypical hemolytic uremic syndrome (aHUS) after kidney transplantation (KT). However, the optimal management of aHUS transplant candidates with anti-Complement Factor H (CFH) antibodies remains debated. In these patients, the benefits of chronic eculizumab administration should be weighed against the risk of fatal infections, repeated hospital admissions, and excessive costs. We report the case of a 45-year-old female patient with CFHR1/CFHR3 homozygous deletion-associated aHUS who underwent deceased-donor KT despite persistently elevated anti-CFH antibody titers. As induction and aHUS prophylaxis, she received a combination of eculizumab and obinutuzumab, a humanized type 2 anti-CD20 moAb. The post-operative course was uneventful. After 1-year of follow-up, she is doing well with excellent allograft function, undetectable anti-CFH antibodies, sustained B-cell depletion, and no signs of aHUS activity. A brief review summarizing current literature on the topic is also included. Although anecdotal, our experience suggests that peri-operative obinutuzumab administration can block anti-CFH antibodies production safely and effectively, thus ensuring long-lasting protection from post-transplant aHUS relapse, at a reasonable cost. For the first time, we have demonstrated in vivo that obinutuzumab B-cell depleting properties are not significantly affected by eculizumab-induced complement inhibition.

Anti-Factor H Antibody-Associated Atypical Hemolytic Uremic Syndrome: A Case Report

Introduction: Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy, caused by dysregulation of the complement alternative pathway. Deletion of the complement factor H-related genes, CFHR1 and CFHR3, together with the presence of CFH autoantibodies are reported in aHUS patients, representing 10% of cases of patients with aHUS. Case presentation: We report here on a case of 4-year-old girl with anti-CFH antibody-associated aHUS. The measurement of complement factors and anti-factor H antibodies, was the main guideline for making an accurate diagnosis and providing the appropriate therapy, with the patient responding positively to plasma exchanges (PEs) and cyclophosphamide pulses. We then, one year after disease onset, continued with glucocorticoids and mycophenolate mofetil (MMF), as maintenance therapy. There were no complications during the therapy other than neutropenia. Now, one year after the cessation of the immune suppression therapy, she is in remission with normal kidney function, no signs of hemolysis, normal C3 levels, and normal range proteinuria. The anti-factor H autoantibody titer decreased but still remained positive, the factor H antigen values remained low all throughout. Close follow-up is applied with frequent urine testing and complete blood count with an intention for early detection of relapse of the disease. Conclusion: The purpose of this case report is to emphasize the value of complement factor measurements and also to separate anti-CFH antibody-associated aHUS as an entity, because immunosuppressive therapy provides an excellent response..

Pediatric atypical hemolytic-uremic syndrome due to auto-antibodies against factor H: is there an interest to combine eculizumab and mycophenolate mofetil?

BACKGROUND

Atypical hemolytic and uremic syndrome (aHUS), a thrombotic micro-angiopathy (TMA) caused by deregulation in the complement pathway, is sometimes due to the presence of anti-complement factor H (CFH) auto-antibodies. The "standard" treatment for such aHUS combines plasma exchange therapy and immunosuppressive drugs. Eculizumab, a monoclonal antibody that blocks the terminal pathway of the complement cascade, could be an interesting alternative in association with an immunosuppressive treatment for maintenance regimen.

CASE-DIAGNOSIS/TREATMENT

We report on two children, diagnosed with mildly severe aHUS due to anti-CFH antibodies, who were treated with the association eculizumab-mycophenolate mofetil (MMF). Neither side effects nor relapses were observed during the 3 years of follow-up; MMF was even progressively tapered and withdrawn successfully in one patient.

CONCLUSIONS

The association of eculizumab and MMF appears to be an effective and safe option in pediatric cases of aHUS due to anti-CFH antibodies of mild severity.

Deficiency of CFHR plasma proteins and autoantibody positive hemolytic uremic syndrome: treatment rationale, outcomes, and monitoring

Deficiency of Complement Factor H Related (CFHR) plasma proteins and Autoantibody Positive Hemolytic Uremic Syndrome (DEAP-HUS) is a subtype of atypical hemolytic uremic syndrome, known to be associated with significant morbidity. Its pathogenesis is linked to the production of IgG autoantibodies against complement factor H, a regulator of the alternative complement pathway. The binding of the autoantibodies to the C terminal of complement factor H interferes with its regulatory function, leading to increased activation of the alternative complement pathway and consequent endothelial cellular damage. Early diagnosis and initiation of appropriate therapy is reported to lead to favorable outcomes. Institution of plasma exchange therapy within 24 h of diagnosis has been shown to rapidly lower antibody levels, leading to clinical improvement. Adjunctive immunosuppression therapy suppresses antibody production and helps in maintaining long-term clinical remission of the disease. Available data advocates a treatment regimen that combines plasma therapy (preferably plasma exchange) and immunosuppression to halt disease process and sustain long-term disease remission.

Successful Treatment of Anti-Factor H Antibody-Associated Atypical Hemolytic Uremic Syndrome

Anti-complement factor H (CFH) autoantibody (Ab)-associated atypical hemolytic uremic syndrome (aHUS) has a poor prognosis in terms of frequent relapses. Although eculizumab is an effective treatment for this type of aHUS, the method of eculizumab discontinuation is not yet established. Herein, we report a case of anti-CFH Ab-associated aHUS in a 6-year-old boy. Eculizumab induction therapy following plasma exchange improved his condition. After 14 months, eculizumab was discontinued because of meningococcal bacteremia. After 6 months of eculizumab cessation, prednisolone (20 mg/alternate days) and mycophenolate mofetil (500 mg/day) were initiated. There were no relapses or increases in anti-CFH Ab titers for 26 months after treatment initiation. We believe that eculizumab induction therapy, following plasma exchange and maintenance therapy with immunosuppressants after eculizumab discontinuation are effective treatments for anti-CFH Ab-related aHUS.

Case Series of 3 Patients Diagnosed With Atypical Hemolytic Uremic Syndrome Successfully Treated With Steroids, Plasmapheresis, and Rituximab

Rationale

Atypical hemolytic uremic syndrome, which has a high probability of chronic kidney disease, morbidity, and mortality, needs to be promptly recognized when patients present with microangiopathic hemolysis.

Presenting Concerns of the Patient

Three patients present with laboratory parameters consistent with a thrombotic microangiopathy. With a suspected diagnosis of thrombotic thrombocytopenic purpura, steroids with plasmapheresis were initiated.

Diagnoses

With ADAMTS13 levels reported normal, the suspected diagnoses were reevaluated. Given ongoing renal impairment, atypical hemolytic uremic syndrome was strongly considered.

Interventions

When local funding issues precluded the prompt use of eculizumab, 4 doses of weekly rituximab were trialed.

Outcome

Over 2 years later, all 3 patients have sustained durable remissions defined by the absence of kidney impairment or laboratory investigations concerning for microangiopathic hemolytic relapse.

Lessons Learned

In cases of a suspected autoimmune mechanism leading to atypical hemolytic uremic syndrome, long-term use of eculizumab may not be required.

Factor H autoantibody is associated with atypical hemolytic uremic syndrome in children in the United Kingdom and Ireland

Factor H autoantibodies can impair complement regulation, resulting in atypical hemolytic uremic syndrome, predominantly in childhood. There are no trials investigating treatment, and clinical practice is only informed by retrospective cohort analysis. Here we examined 175 children presenting with atypical hemolytic uremic syndrome in the United Kingdom and Ireland for factor H autoantibodies that included 17 children with titers above the international standard. Of the 17, seven had a concomitant rare genetic variant in a gene encoding a complement pathway component or regulator. Two children received supportive treatment; both developed established renal failure. Plasma exchange was associated with a poor rate of renal recovery in seven of 11 treated. Six patients treated with eculizumab recovered renal function. Contrary to global practice, immunosuppressive therapy to prevent relapse in plasma exchange-treated patients was not adopted due to concerns over treatment-associated complications. Without immunosuppression, the relapse rate was high (five of seven). However, reintroduction of treatment resulted in recovery of renal function. All patients treated with eculizumab achieved sustained remission. Five patients received renal transplants without specific factor H autoantibody-targeted treatment with recurrence in one who also had a functionally significant CFI mutation. Thus, our current practice is to initiate eculizumab therapy for treatment of factor H autoantibody-mediated atypical hemolytic uremic syndrome rather than plasma exchange with or without immunosuppression. Based on this retrospective analysis we see no suggestion of inferior treatment, albeit the strength of our conclusions is limited by the small sample size.

Haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is defined by the simultaneous occurrence of nonimmune haemolytic anaemia, thrombocytopenia and acute renal failure. This leads to the pathological lesion termed thrombotic microangiopathy, which mainly affects the kidney, as well as other organs. HUS is associated with endothelial cell injury and platelet activation, although the underlying cause may differ. Most cases of HUS are associated with gastrointestinal infection with Shiga toxin-producing enterohaemorrhagic Escherichia coli (EHEC) strains. Atypical HUS (aHUS) is associated with complement dysregulation due to mutations or autoantibodies. In this review, we will describe the causes of HUS. In addition, we will review the clinical, pathological, haematological and biochemical features, epidemiology and pathogenetic mechanisms as well as the biochemical, microbiological, immunological and genetic investigations leading to diagnosis. Understanding the underlying mechanisms of the different subtypes of HUS enables tailoring of appropriate treatment and management. To date, there is no specific treatment for EHEC-associated HUS but patients benefit from supportive care, whereas patients with aHUS are effectively treated with anti-C5 antibody to prevent recurrences, both before and after renal transplantation.

Efficacy of rituximab and plasmapharesis in an adult patient with antifactor H autoantibody-associated hemolytic uremic syndrome: A case report and literature review

Antifactor H antibody (anti-CFHAb) is found in 6% to 25% cases of atypical hemolytic uremic syndrome (aHUS) in children, but has been only exceptionally reported in adults. There is no consensus about the best treatment for this type of aHUS. We report the case of an adult patient treated successfully with plasma exchange (PE), steroids, and rituximab.A 27-year-old Caucasian male presented to hospital with anemia, thrombocytopenia, and acute renal failure. One week earlier, he had digestive problems with diarrhea. The diagnosis of anti-CFHAb-associated aHUS (82,000 AU/mL) without CFHR gene mutations was established.He received Rituximab 375 mg/m (4 pulses) with PE and steroids. This treatment achieved renal and hematological remission at day (D) 31 and negative anti-CFHAb at D45 (<100 AU/mL). At D76, a fifth rituximab pulse was performed while CD19 was higher than 10/mm. Steroids were stopped at month (M) 9. The patient has not relapsed during long-term follow-up (M39).Rituximab therapy can be considered for anti-CFHAb-associated aHUS. Monitoring of anti-CFHAb titer may help to guide maintenance therapeutic strategies including Rituximab infusion.

Can eculizumab be discontinued in aHUS?: Case report and review of the literature

BACKGROUND

The management of atypical hemolytic uremic syndrome (aHUS) has evolved into better control of thrombotic microangiopathy (TMA) and recovery of renal functions since the recent introduction of the terminal complement cascade blocker, eculizumab, into clinical use. Better characterization of genotype-phenotype relations has become possible with genetic and clinical studies. However, these advances brought up some important issues, such as the possibility and timing of discontinuation of eculizumab and strategy of follow-up that need to be enlightened.

CASE SUMMARY

One of our aHUS cases with a novel complement factor H mutation, who developed unusual laboratory findings (thrombocytopenia and mild creatinine elevation without other features of TMA) following discontinuation of eculizumab was presented. Literature and case reports relevant to discontinuation of eculizumab in aHUS patients were reviewed.

CONCLUSION

Limited experience suggests that the risk of recurrence of TMA following discontinuation of eculizumab is relatively low for patients with MCP mutations, homozygous CFHR3/R1 deletions, anti-CFH antibodies, CFI mutations, and no identifiable mutations, whereas there is a major risk for patients with CFH mutations. Early detection of TMA recurrence and prompt retreatment with eculizumab seem to be efficient in controlling of TMA and restoration of kidney functions.

Anti-complement-factor H-associated glomerulopathies

Atypical haemolytic uraemic syndrome (aHUS), an important cause of acute kidney injury, is characterized by dysregulation of the complement pathway, frequent need for dialysis, and progression to end-stage renal disease. Autoantibodies against complement factor H (FH), the main plasma regulatory protein of the alternative pathway of the complement system, account for a considerable proportion of children with aHUS. The autoantibodies are usually associated with the occurrence of a homozygous deletion in the genes encoding the FH-related proteins FHR1 and FHR3. High levels of autoantibodies, noted at the onset of disease and during relapses, induce functional deficiency of FH, whereas their decline, in response to plasma exchanges and/or immunosuppressive therapy, is associated with disease remission. Management with plasma exchange and immunosuppression is remarkably effective in inducing and maintaining remission in aHUS associated with FH autoantibodies, whereas terminal complement blockade with eculizumab is considered the most effective therapy in other forms of aHUS. Anti-FH autoantibodies are also detected in a small proportion of patients with C3 glomerulopathies, which are characterized by chronic glomerular injury mediated by activation of the alternative complement pathway and predominant C3 deposits on renal histology.

An international consensus approach to the management of atypical hemolytic uremic syndrome in children

Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of complement dysregulation. This advance facilitated the development of novel, rational treatment options targeting terminal complement activation, e.g., using an anti-C5 antibody (eculizumab). We review treatment and patient management issues related to this therapeutic approach. We present consensus clinical practice recommendations generated by HUS International, an international expert group of clinicians and basic scientists with a focused interest in HUS. We aim to address the following questions of high relevance to daily clinical practice: Which complement investigations should be done and when? What is the importance of anti-factor H antibody detection? Who should be treated with eculizumab? Is plasma exchange therapy still needed? When should eculizumab therapy be initiated? How and when should complement blockade be monitored? Can the approved treatment schedule be modified? What approach should be taken to kidney and/or combined liver-kidney transplantation? How should we limit the risk of meningococcal infection under complement blockade therapy? A pressing question today regards the treatment duration. We discuss the need for prospective studies to establish evidence-based criteria for the continuation or cessation of anticomplement therapy in patients with and without identified complement mutations.

Plasma exchange for paediatric kidney disease-indications and outcomes: a single-centre experience

BACKGROUND

Outcome data in paediatrics regarding the use of plasmapheresis for immunological kidney disease are scarce.

OBJECTIVES

We aimed to evaluate the role of plasmapheresis in children presenting with severe renal impairment secondary to immunological kidney diseases.

METHODS

A retrospective chart review of children admitted between January 2009 and August 2013 to the Paediatric Nephrology Unit, Christian Medical College, Vellore, India, and requiring plasma exchange was undertaken. Demographic and clinical data were studied and descriptive statistics applied for analysis.

RESULTS

Sixteen children underwent plasmapheresis with a male:female ratio of 10:6 and a mean age of 10.2 years (range 5-15 years). Twelve children had atypical haemolytic uraemic syndrome, two had anti-glomerular basement disease and one each had lupus nephritis with neurological manifestation and anti-nuclear cytoplasmic antibody-associated vasculitis. The mean serum creatinine at presentation was 6.52 [interquartile range (IQR) 4.96-7.85] mg/dL with a mean eGFR of 43 (IQR 27.54-56.7) mL/min/1.73 m(2). Other presenting features included nephrotic range proteinuria (69%), gross haematuria (27%), hypertension (94%) and seizures (37.5%). All children received 1.5 times plasma volume plasmapheresis (mean 11 sessions, range 5-26), dialysis and immunosuppressive therapy. The mean duration of follow-up was 4 months (range 2-24 months) with a majority of the children (15/16, 93.75%) surviving acute illness. One child died of overwhelming sepsis and another was lost to follow-up. Of the survivors, eight had eGFR >60 mL/min/1.73 m(2), while eGFR was 15-60 mL/min/1.73 m(2) in the remaining six children. Eight children were still requiring antihypertensive medications and two were continuing peritoneal dialysis at the last follow-up. Thus early introduction of plasmapheresis along with other supportive therapy in immunological kidney disease may improve outcome.

Successful living-related renal transplantation in a patient with factor H antibody-associated atypical hemolytic uremic syndrome

CFH-Ab-associated aHUS requires different diagnostic and therapeutic approaches and then the genetically defined aHUS forms. The risk of post-transplant recurrence with graft dysfunction in CFH-Ab aHUS is not well documented. It is suggested that recurrence can be expected if a significant CFH-Ab load persists at the time of transplantation. A pretransplant procedure to reduce CFH-Ab titer seems reasonable, but accurate recommendations are lacking. Whether further prophylactic interventions after transplantation are necessary has to be decided on an individual basis. We report the case of a late diagnosed CFH-Ab HUS with initial ESRD and a successful living-related renal transplantation over a post-transplant period of four and a half years on the basis of a prophylactic pretransplant IVIG admission.

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.

Effect of plasma exchange and immunosuppressive medications on antibody titers and outcome in anti-complement factor H antibody-associated hemolytic uremic syndrome

BACKGROUND

Anti-complement factor H (anti-CFH) antibody-associated hemolytic uremic syndrome (HUS) is an important cause of acute kidney injury in Indian children. While management comprises plasma exchange and immunosuppression, information on the impact on serial antibody titers and outcomes is limited.

METHODS

This retrospective study included 45 patients with anti-CFH-associated HUS who were followed for ≥12 months. Following the initial plasma exchange sessions, patients received prednisolone and either intravenous (IV) cyclophosphamide (n = 31) or IV rituximab (n = 14), followed by maintenance immunosuppression.

RESULTS

The median anti-CFH antibody titers fell from 3,215.5 [interquartile range (IQR) 1,977.9-8,453.9 to 414.6 (IQR 251.6-1,368.2) AU/ml with plasma exchange therapy (P < 0.0001), and the decline was similar with three, five, or seven plasma exchange sessions (P = 0.08). Serial anti-CFH titers were similar in patients receiving IV cyclophosphamide- and rituximab-based regimens during the 12-month follow-up (P = 0.63). Renal outcomes and relapse frequencies at the 15.4-month follow-up were comparable. Seven patients relapsed 6.5 (IQR 2.2-12.3) months from treatment onset. Patients with relapse had higher antibody titers during remission (P = 0.017). Titers of ≥1,300 AU/ml at 6 months predicted subsequent relapses.

CONCLUSIONS

Our patients with anti-CFH antibody-associated HUS showed a significant fall in antibody titers following daily plasma exchange sessions. Therapy with cyclophosphamide- or rituximab-based regimens was associated with similar outcomes and a comparable decline in antibody titers.

Atypical hemolytic-uremic syndrome: a case report and literature review

Patient: Female, 59

Final Diagnosis: Atyipcal hemolytic uremic syndrome

Symptoms: Delirium • headache

Medication: —

Clinical Procedure: —

Specialty: Hematology

Anti-factor H autoantibody-associated hemolytic uremic syndrome: the earlier diagnosed and treated, the better

Atypical hemolytic uremic syndrome (HUS) secondary to anti-factor H autoantibodies has a poor prognosis. The study by Sinha et al. of a large cohort of Indian children makes a substantial contribution to improved management of this form of HUS by showing that standardized titration of anti-factor H autoantibodies is applicable worldwide and that early treatment initiation and guidance of maintenance treatment by autoantibody titer monitoring significantly improve outcomes.

Autoantibodies to CD59, CD55, CD46 or CD35 are not associated with atypical haemolytic uraemic syndrome (aHUS)

Autoantibody formation against Factor H (FH) is found in 7-10% of patients who are diagnosed with atypical haemolytic uraemic syndrome (aHUS). These autoantibodies predominately target the C-terminal cell binding recognition domain of FH and are associated with absence of FHR1. Additional autoantibodies have also been identified in association with aHUS, for example autoantibodies to Factor I. Based on this, and that there are genetic mutations in other complement regulators and activators associated with aHUS, we hypothesised that other complement regulator proteins, particularly surface bound regulators in the kidney, might be the target for autoantibody formation in aHUS. Therefore, we assayed serum derived from 89 patients in the Newcastle aHUS cohort for the presence of autoantibodies to CD46 (membrane cofactor protein, MCP), CD55 (decay accelerating factor, DAF), CD35 (complement receptor type 1, CR1; TP10) and CD59. We also assayed 100 healthy blood donors to establish the normal levels of reactivity towards these proteins in the general population. Recombinant proteins CD46 and CD55 (purified from Escherichia coli) as well as soluble CR1 (CD35) and oligomeric C4BP-CD59 (purified from eukaryotic cell media) were used in ELISA to detect high responders. False positive results were established though Western blot and flow cytometric analysis. After excluding false positive responders to bacterial proteins in the CD46 and CD55 preparations, and responses to blood group antigens in CD35, we found no significant level of patient serum IgG reactivity with CD46, CD55, CD35 or CD59 above that detected in the normal population. These results suggest that membrane anchored complement regulators are not a target for autoantibody generation in aHUS.

Podocyte dysfunction in atypical haemolytic uraemic syndrome

Genetic or autoimmune defects that lead to dysregulation of the alternative pathway of complement have been associated with the development of atypical haemolytic uraemic syndrome (aHUS), which is characterized by thrombocytopenia, haemolytic anaemia and acute kidney injury. The relationship between aHUS, podocyte dysfunction and the resultant proteinuria has not been adequately investigated. However, the report of mutations in diacylglycerol kinase ε (DGKE) as a cause of recessive infantile aHUS characterized by proteinuria, highlighted podocyte dysfunction as a potential complication of aHUS. DGKE deficiency was originally thought to trigger aHUS through pathogenetic mechanisms distinct from complement dysregulation; however, emerging findings suggest an interplay between DGKE and complement systems. Podocyte dysfunction with nephrotic-range proteinuria can also occur in forms of aHUS associated with genetic or autoimmune complement dysregulation without evidence of DGKE mutations. Furthermore, proteinuric glomerulonephritides can be complicated by aHUS, possibly as a consequence of podocyte dysfunction inducing endothelial injury and prothrombotic abnormalities.

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.

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.