Novel C3 mutation p.Lys65Gln in aHUS affects complement factor H binding

Background

Atypical hemolytic uremic syndrome (aHUS) is associated with mutations affecting complement proteins and regulators and with autoantibodies against complement factor H (CFH). Approximately half of the aHUS patients progress to end-stage renal disease. DNA analysis of the risk factor genes is important for prognosis of aHUS recurrence after renal transplantation.

Methods

Mutational screening of C3 encoding the central complement component was performed by Sanger sequencing in 70 aHUS patients. Mutated and wild type recombinant C3b proteins were produced and their affinity to CFH was analyzed by ELISA.

Results

A single novel missense change p.Lys65Gln in C3 was found in 3 aHUS patients. The alteration leads to decreased binding of C3b to CFH in vitro. All three patients acquired the illness as adults and had a first aHUS episode after renal transplantation or suffered recurrence of the disease after transplantation.

Conclusions

The novel C3 change was found in 3 aHUS patients. It results in decreased C3b binding to CFH and thus might lead to impaired C3b inactivation in vivo. The p.Lys65Gln is likely to be associated with aHUS after kidney transplantation and, therefore, might be an important prognostic factor.     

Use of eculizumab and plasma exchange in successful combined liver–kidney transplantation in a case of atypical HUS associated with complement factor H mutation

Background

Atypical hemolytic uremic syndrome (aHUS) evolves into end-stage renal failure in nearly half of affected patients and is associated with defective regulation of the alternative complement pathway. Patients with a complement factor H (CFH) mutation have a 30–100% risk of graft loss due to aHUS recurrence or graft thrombosis. Since CFH is produced predominantly by the liver, combined liver–kidney transplant is a curative treatment option. One major unexpected risk includes liver failure secondary to uncontrolled complement activation. We report a successful combined liver–kidney transplantation with perioperative plasma exchange and use of the humanized anti-C5 monoclonal antibody eculizumab.

Case Diagnosis/Treatment

An 11-month-old female presented with oliguric renal failure after 3 weeks of flu-like symptoms in the absence of diarrhea. Following the identification of Escherichia coli 0157:H7 in her stool, she was discharged home on peritoneal dialysis with a diagnosis of Shiga toxin-associated HUS. Three months later, she developed severe anemia, thrombocytopenia, and neurological involvement. aHUS was diagnosed and confirmed, and genetic testing revealed a mutation in CFH SCR20. Once donor organs became available, she received preoperative plasma exchange followed by eculizumab infusion with intra-operative fresh frozen plasma prior to combined liver–kidney transplant. At 19 months post-transplant, she continues to have excellent allograft and liver function without signs of disease recurrence.

Conclusion

Perioperative use of eculizumab in conjunction with plasma exchange during simultaneous liver–kidney transplant can be used to inhibit terminal complement activity, thereby optimizing successful transplantation by reducing the risk of graft thrombosis.     

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.     

A novel hybrid CFHR1/CFH gene causes atypical hemolytic uremic syndrome

Background

Mutations in complement factor H (CFH) are associated with complement dysregulation and the development of an aggressive form of atypical hemolytic uremic syndrome (aHUS) that progresses to end-stage renal disease (ESRD) and in most patients has a high rate of recurrence following transplantation. Sequence analysis of CFH and its downstream complement factor H-related genes (CFHR1-5) reveals several macrohomologous blocks caused by large genomic duplications. This high degree of sequence identity renders this area susceptible to nonallelic homologous recombination (NAHR) events, resulting in large-scale deletions, duplications, and the generation of hybrid CFH genes.

Case-Diagnosis

Here, we report the finding of a novel CFHR1/CFH hybrid gene created by a de novo NAHR event in a 14-year-old girl with aHUS. The resulting fusion protein contains the first three short consensus repeats (SCRs) of CFHR1 and the terminal two SCRs of CFH.

Conclusions

This finding demonstrates a novel pathogenic mechanism for the development of aHUS. Additionally, since standard Sanger sequencing is unable to detect such rearrangements, all aHUS patients should receive comprehensive genetic screening that includes analysis of copy number variation in order to identify patients with poor clinical prognoses.     

Macrovascular involvement in a child with atypical hemolytic uremic syndrome

Background

Atypical hemolytic uremic syndrome (aHUS) is a disorder of the complement system which leads to thrombotic microangiopathy. It is caused by either acquired or hereditary defects in the activation or regulation of the alternative complement pathway and is therefore considered to be a disease of local complement dysregulation in microvasculature with predominantly renal involvement. However, extrarenal manifestations are observed in approximately one-fifth of aHUS patients, with the myocardium and central nervous system (CNS) being involved most often. Additionally, there have been a few reports of aHUS with cerebral artery stenoses or periphereal gangrene, suggesting the possibility of ‘macrovascular’ involvement in aHUS.

Case-diagnosis/treatment

We present a child with early onset aHUS and a C3 gain-of-function mutation who developed cerebral artery stenoses, leading ultimately to death due to a massive stroke 9 days after successful renal transplantation under prophylactic eculizumab treatment. Similar cases described in the literature are also briefly summarized.

Conclusions

The disease course in our patient with aHUS confirms that dysregulated complement activation can induce arterial steno-occlusive lesions in the absence of acute episodes of HUS. Further studies are required to document the frequency of such macrovascular complications and the role of eculizumab treatment in preventing their development and progression.     

Eculizumab long-term therapy for pediatric renal transplant in aHUS with CFH/CFHR1 hybrid gene

Background

Atypical hemolytic uremic syndrome (aHUS) is a form of thrombotic microangiopathy (TMA) caused by dysregulation of the complement system. Outcomes of kidney transplantation are poor owing to aHUS recurrence and loss of graft. Patients carrying CFH mutations or CFH/CFHR1 hybrid genes present a very high risk of recurrence despite preventive plasmapheresis. Evaluation of recent data suggests that prophylactic eculizumab pretransplant might be the preferred therapy if available.

Case-diagnosis/treatment

We report 3-year follow-up data in a 9-year-old boy with aHUS and successful renal transplant treated with prophylactic eculizumab without recurrence. He presented with aHUS at age 3, irreversible renal failure and uncontrolled severe hypertension with concentric left ventricular hypertrophy, recurrent acute pulmonary edema, and congestive heart failure despite five hypotensive agents and bilateral nephrectomy. Complement analysis demonstrated the presence of a CFH/CFHR1 hybrid gene inherited from his mother and a SNP risk CFH haplotype inherited from his father. Kidney transplant was performed with prophylactic eculizumab and subsequent fortnightly administration. Three years post-transplant, graft function remains stable (serum creatinine 0.9 mg/dl), hypertension is controlled, no left ventricular hypertrophy, no opportunistic infections, and negative clinical chemistry parameters for hemolysis.

Conclusion

Eculizumab is a safe and effective therapy for preventing TMA recurrence and provides long-term graft function in aHUS with the CFH/CFHR1 hybrid gene.     

Eculizumab therapy in a child with hemolytic uremic syndrome and CFI mutation

Background

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in childhood. It usually occurs after a prodromal episode of diarrhea and it leads to significant morbidity and mortality during the acute phase. However, cases that start as diarrhea-positive HUS whose renal function fail to recover should be screened for genetic disorders of the complement system, which is called atypical HUS (aHUS).

Case-Diagnosis/Treatment

We herein report a 10-year-old girl, who initially came with bloody diarrhea and had features of HUS with delayed renal and hematological recovery despite plasma therapy. Eculizumab (600 mg/week) was initiated on day 15 for atypical presentation and later a complement factor I (CFI) mutation was detected. The girl recovered diuresis within 24 h and after the third eculizumab infusion, hemoglobin, platelet, and C3 levels normalized; renal function improved; and proteinuria completely disappeared in 2 weeks.

Conclusion

It is our belief that eculizumab can be the treatment of choice in children who have plasma exchange-refractory HUS with defective regulation of the alternative complement pathway.     

Atypical HUS due to factor H antibodies in an adult patient successfully treated with eculizumab

Background: Anti-complement factor H (CFH) antibodies is an extremely rare cause of atypical hemolytic uremic syndrome (aHUS) in adults, with less than 10 cases reported thus far. Although infectious diarrhea is a common inciting trigger for aHUS episode, there are no reports of an association with inflammatory bowel disease. Eculizumab is an emerging treatment for aHUS. Eculizumab has not been reported thus far to be given for aHUS due to anti-CFH antibodies. We report here for the first time on an adult patient with ulcerative colitis (UC) who developed aHUS due to anti-CFH antibodies, presented with decreased serum levels of both C3 and C4. She had an excellent response to treatment with eculizumab. Case presentation: A 27-year-old Caucasian woman, who suffered from steroid-dependent UC, was admitted with microangiopathic hemolytic anemia and acute kidney injury with nephrotic syndrome. ADAMTS 13 was normal and comprehensive workout for secondary causes of HUS was negative. Both serum complement level of C3 and C4 were low. Kidney biopsy was compatible with the diagnosis of HUS with negative immunofluorescence. Because of only partial response to plasma exchange and high dose steroids, eculizumab was commenced. After two weeks signs of microangiopathy subsided, and kidney function began to recover. Few months after the diagnosis, a complement components investigation revealed antibodies against CFH at high titer of 2000 arbitrary units. Today her creatinine is stable with no proteinuria and no signs of HUS.     

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

Background

Anti-complement factor H (CFH) autoantibody (Ab)-associated atypical hemolytic uremic syndrome (aHUS) has a poor prognosis, but no consensus exists on its treatment.

Methods

We report the follow-up of four children with anti-CFH Ab (8,000 to >32,000 arbitrary units)-associated aHUS after plasma exchanges (PEs), prednisone, and cyclophosphamide pulse therapy with the evolution of anti-CFH Ab titers and kidney function.

Results

Patient 1 received PEs + prednisone + cyclophosphamide pulses after two relapses following PEs and then PEs + rituximab. The other three patients were treated with PEs + prednisone + cyclophosphamide pulses as a first-line therapy. In our four patients, the induction protocol combining PEs + prednisone + cyclophosphamide pulses led to a rapid and sustained remission up to 6 years, 4 years and 4 months without any maintenance therapy. Kidney function was normal and anti-CFH Ab titer decreased, but remained detectable during remission without any clinical or biological signs of relapse.

Conclusions

We demonstrate the long-term efficiency and safety of cyclophosphamide pulses combined with PEs and prednisone in anti-CFH Ab-associated aHUS leading to a prolonged decrease in anti-CFH Ab titers and prevention of relapses without the need for maintenance therapy.     

Neonatal onset atypical hemolytic uremic syndrome successfully treated with eculizumab

Background

Atypical hemolytic uremic syndrome (aHUS) is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. Neonatal cases are extremely uncommon. Plasma therapy is the first choice therapy in patients with aHUS based on the belief of an underlying complement dysregulation. Alternatively, eculizumab, which targets complement 5, is used to block complement activation.

Case-diagnosis/treatment

Sudden onset macroscopic hematuria, hypertension, and bruises over the entire body were noted in a 5 day-old newborn. Investigations revealed hemolytic anemia, thrombocytopenia, renal impairment, and a low serum C3, leading to the diagnosis of aHUS. Fresh frozen plasma (FFP) infusions and peritoneal dialysis for acute kidney injury were initiated. This approach yielded full renal and hematological remission. The patient was discharged with FFP infusions, but subsequently developed three life-threatening disease recurrences at 1, 3, and 6 months of age. The last relapse presented with uncontrolled hypertension and impaired renal function while the patient was receiving FFP infusions. After the first dose of eculizumab, his renal and hematological parameters returned to normal and his blood pressure normalized. Genetic screening of the CFH gene revealed a novel homozygous p. Tyr1177Cys mutation.

Conclusion

Eculizumab can be considered as an alternative to plasma therapy in the treatment of specific patients with aHUS, even in infants.     

Hemolytic uremic syndrome complicating Mycoplasma pneumoniae infection

Background

Mycoplasma pneumoniae can cause various extrapulmonary manifestations but, to our knowledge, no case of Mycoplasma pneumoniae associated with hemolytic uremic syndrome (HUS) has been reported.

Case-Diagnosis/Treatment

We describe a 1-year-old boy with M. pneumoniae respiratory tract infection and associated microangiopathic hemolytic anemia, slightly decreased platelet count and mild renal impairment, suggesting a diagnosis of HUS. Assuming M. pneumoniae infection was the cause of HUS in this case, the different possible mechanisms, including an atypical HUS due to preexisting complement dysregulation, an alternative complement pathway activation induced by M. pneumoniae infection at the acute phase, an autoimmune disorder, and a direct role of the bacteria in inducing endothelial injury, are discussed. The signs of HUS resolved with treatment of the M. pneumoniae infection.

Conclusions

Hemolytic uremic syndrome may be an unusual complication of M. pneumoniae infection.     

Liver transplantation for aHUS: still needed in the eculizumab era?

Background

The risk of disease recurrence after a kidney transplant is high in patients with atypical hemolytic uremic syndrome (aHUS) and mutations in the complement factor H (FH) gene (CFH). Since FH is mostly produced by the liver, a kidney transplant does not correct the genetic defect. The anti-C5 antibody eculizumab prevents post-transplant aHUS recurrence, but it does not cure the disease. Combined liver–kidney transplantation has been performed in few patients with CFH mutations based on the rationale that liver replacement provides a source of normal FH.

Methods

We report the 9-year follow-up of a child with aHUS and a CFH mutation, including clinical data, extensive genetic characterization, and complement profile in the circulation and at endothelial level. The outcome of kidney and liver transplants performed separately 3 years apart are reported.

Results

The patient showed incomplete response to plasma, with relapsing episodes, progression to end-stage renal disease, and endothelial-restricted complement dysregulation. Eculizumab prophylaxis post-kidney transplant did not achieve sustained remission, leaving the child at risk of disease recurrence. A liver graft given 3 years after the kidney transplant completely abrogated endothelial complement activation and allowed eculizumab withdrawal.

Conclusions

Liver transplant may definitely cure aHUS and represents an option for patients with suboptimal response to eculizumab.

     

Differential impact of complement mutations on clinical characteristics in atypical hemolytic uremic syndrome

Mutations in factor H (CFH), factor I (IF), and membrane cofactor protein (MCP) genes have been described as risk factors for atypical hemolytic uremic syndrome (aHUS). This study analyzed the impact of complement mutations on the outcome of 46 children with aHUS. A total of 52% of patients had mutations in one or two of known susceptibility factors (22, 13, and 15% of patients with CFH, IF, or MCP mutations, respectively; 2% with CFH+IF mutations). Age <3 mo at onset seems to be characteristic of CFH and IF mutation-associated aHUS. The most severe prognosis was in the CFH mutation group, 60% of whom reached ESRD or died within <1 yr. Only 30% of CFH mutations were localized in SCR20. MCP mutation-associated HUS has a relapsing course, but none of the children reached ESRD at 1 yr. Half of patients with IF mutation had a rapid evolution to ESRD, and half recovered. Plasmatherapy seemed to have a beneficial effect in one third of patients from all groups except for the MCP mutation group. Only eight (33%) of 24 kidney transplantations that were performed in 15 patients were successful. Graft failures were due to early graft thrombosis (50%) or HUS recurrence. In conclusion, outcome of HUS in patients with CFH mutation is catastrophic, and posttransplantation outcome is poor in all groups except for the MCP mutation group. New therapies are urgently needed, and further research should elucidate the unexplained HUS group.     

Atypical hemolytic uremic syndrome in children: complement mutations and clinical characteristics

Background

Mutations in complement factor H (CFH), factor I (CFI), factor B (CFB), thrombomodulin (THBD), C3 and membrane cofactor protein (MCP), and autoantibodies against factor H (αFH) with or without a homozygous deletion in CFH-related protein 1 and 3 (?CFHR1/3) predispose development of atypical hemolytic uremic syndrome (aHUS).

Methods

Different mutations in genes encoding complement proteins in 45 pediatric aHUS patients were retrospectively linked with clinical features, treatment, and outcome.

Results

In 47% of the study participants, potentially pathogenic genetic anomalies were found (5xCFH, 4xMCP, and 4xC3, 3xCFI, 2xCFB, 6xαFH, of which five had ?CFHR1/3); four patients carried combined genetic defects or a mutation, together with αFH. In the majority (87%), disease onset was preceeded by a triggering event; in 25% of cases diarrhea was the presenting symptom. More than 50% had normal serum C3 levels at presentation. Relapses were seen in half of the patients, and there was renal graft failure in all except one case following transplant.

Conclusions

Performing adequate DNA analysis is essential for treatment and positive outcome in children with aHUS. The impact of intensive initial therapy and renal replacement therapy, as well as the high risk of recurrence of aHUS in renal transplant, warrants further understanding of the pathogenesis, which will lead to better treatment options.     

Long-term eculizumab improves clinical outcomes in atypical hemolytic uremic syndrome

Background

Atypical hemolytic uremic syndrome (aHUS) is a rare genetic disorder caused by chronic uncontrolled complement activation.

Case-diagnosis/treatment

We present a 4-year-old girl with aHUS who had multiple severe clinical manifestations of thrombotic microangiopathy (TMA) including acute kidney injury, dilated cardiomyopathy, and cardiorespiratory arrest. She was managed with intensive plasma exchange and hemodialysis, which could not halt the progression of TMA. The initial single dose of eculizumab only temporarily improved the clinical symptoms of TMA. Sustained improvement of renal, hematological, and cardiac values were only achieved upon institution of chronic treatment with eculizumab. During long-term treatment with eculizumab (>2.5 years), she has had no further clinical manifestations of TMA, and required neither plasma exchange nor hemodialysis.

Conclusion

Chronic eculizumab treatment was associated with control of complement-mediated TMA and sustained long-term improvement in renal and cardiac function.     

Neurologic involvement in atypical hemolytic uremic syndrome and successful treatment with eculizumab

Background

Atypical hemolytic uremic syndrome (aHUS) is associated with defective regulation of the complement pathway. Neurological involvement is the most common extrarenal complication and represents a major cause of mortality and morbidity.

Case-diagnosis/treatment

Two girls aged 11 and 6 years, respectively, developed aHUS and were treated immediately with plasma exchange (PE) and fresh frozen plasma infusion (PI). Although initial improvement in renal function was seen in both cases, the first patient showed progressing thrombotic microangiopathy (TMA) despite daily PE, and neurological manifestations (seizures, vision loss, loss of balance, and confusion) developed after 1 month. The second patient developed cerebral TMA (seizures, vision loss, and nystagmus) 6 days after initial presentation and remained unresponsive to PE/PI. Neurological symptoms were similar in both patients, even though they had different complement protein mutations. Treatment with eculizumab achieved complete control of neurological symptoms within 24 h and gradually normalized hematological and renal parameters in both children.

Conclusions

Based on our two cases, we conclude that eculizumab is a rapid-acting, effective, and life-saving treatment for pediatric patients with aHUS and severe neurological involvement, which works by inhibiting complement-mediated TMA in the kidney and other organs, such as the brain.     

Eculizumab and Belatacept for De Novo Atypical Hemolytic Uremic Syndrome Associated With CFHR3-CFHR1 Deletion in a Kidney Transplant Recipient: A Case Report

Background

Atypical hemolytic uremic syndrome (aHUS) is associated with significant morbidity and mortality and occurs due to genetic or acquired abnormalities that result in the dysregulation of the alternative complement pathway.

The development of atypical hemolytic uremic syndrome depends on complement C5

Gene variants in the alternative pathway of the complement system strongly associate with atypical hemolytic uremic syndrome (aHUS), presumably by predisposing to increased complement activation within the kidney. Complement factor H (CFH) is the major regulator of complement activation through the alternative pathway. Factor H-deficient mice transgenically expressing a mutant CFH protein (Cfh(-/-).FHΔ16-20) that functionally mimics the CFH mutations reported in aHUS patients spontaneously develop thrombotic microangiopathy. To investigate the role of complement C5 activation in this aHUS model, we generated C5-deficient Cfh(-/-).FHΔ16-20 mice. Both C5-sufficient and C5-deficient Cfh(-/-).FHΔ16-20 mice had abnormal C3 deposition within the kidney, but spontaneous aHUS did not develop in any of the C5-deficient mice. Furthermore, although Cfh(-/-).FHΔ16-20 animals demonstrated marked hypersensitivity to experimentally triggered renal injury, animals with concomitant C5 deficiency did not. These data demonstrate a critical role for C5 activation in both spontaneous aHUS and experimentally triggered renal injury in animals with defective complement factor H function. This study provides a rationale to investigate therapeutic inhibition of C5 in human aHUS.     

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.