Efficacy and safety of eculizumab in childhood atypical hemolytic uremic syndrome in Japan

Advances in Research on the Release of von Willebrand Factor from Endothelial Cells through the Membrane Attack Complex C5b-9 in Sepsis

Sepsis, a lethal organ dysfunction syndrome driven by aberrant host responses to infection, intertwines excessive inflammatory responses and dysregulated coagulation processes in its pathophysiology. Emerging research reveals the complement terminal membrane attack complex C5b-9 orchestrates ultralarge von Willebrand factor (ULVWF) release from vascular endothelial cells (ECs) through multifaceted mechanisms: C5b-9 compromises EC membrane integrity, activates calcium influx cascades, and provokes NLRP3 inflammasome signaling, triggering massive exocytosis of ULVWF stored within Weibel-Palade bodies (WPBs). When ADAMTS13 activity falters, undegraded ULVWF complexes with platelets to spawn microthrombi, precipitating microvascular occlusion and multiorgan collapse. Strikingly, elevated plasma von Willebrand factor (vWF) antigen levels in sepsis patients correlate robustly with endothelial injury, thrombocytopenia, and mortality-underscoring C5b-9-driven vWF release as a linchpin of septic coagulopathy. Current therapeutic strategies targeting these pathways, including recombinant ADAMTS13 (rhADAMTS13), N-acetylcysteine (NAC), and complement inhibitors like eculizumab, face limitations in clinical translation, necessitating further validation of their efficacy. Additionally, investigating complement regulatory molecules such as CD59 may unlock novel therapeutic avenues. Deciphering the intricate interplay within the C5b-9-vWF axis and advancing precision therapies hold transformative potential for ameliorating sepsis outcomes.

Acute eculizumab treatment in a pediatric patient with AQP4-IgG+ NMOSD

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disorder that occurs in children and adults.

CASE

We report a case of a 10-year-old female with AQP4+ NMOSD who presented with paraparesis from longitudinally extensive transverse myelitis (LETM) from C2 to the conus medullaris. The patient showed gradual improvement in strength and sensation with solumedrol and plasma exchange therapy. Given her severe presentation, eculizumab therapy was also initiated acutely. She had near complete recovery, although she developed a myelitis relapse during transition to rituximab treatment.

CONCLUSION

This case demonstrates the role of eculizumab as a safe and effective treatment option in treating an acute attack of pediatric AQP4+ NMOSD. More data are needed to understand the risk of relapse if transitioning off of these highly effective medications.

Eculizumab treatment in paediatric patients diagnosed with aHUS after haematopoietic stem cell transplantation: a HSCT-TMA case series from Japanese aHUS post-marketing surveillance

Haematopoietic stem-cell transplantation (HSCT)-associated thrombotic microangiopathy (HSCT-TMA) is a serious complication with high mortality. Accumulating evidence suggests that complement dysregulation is potentially involved in the development of HSCT-TMA. We retrospectively analysed the clinical characteristics and outcomes of thirteen paediatric patients who were diagnosed with atypical haemolytic uremic syndrome and treated with eculizumab to manage HSCT-TMA during post-marketing surveillance in Japan. The median time from HSCT to TMA was 31 days (Interquartile range, IQR;21-58) and the median doses of eculizumab was three (IQR;2-5). Seven patients (54%) were alive at the last follow-up while six died due to complications related to HSCT. Six of seven survivors initiated eculizumab after insufficient response to plasma therapy. Following eculizumab treatment, median platelet counts and LDH levels in all survivors significantly improved and renal function improved in 4/7 patients. All survivors possessed potential risk factors of complement overactivation. During the follow-up period after eculizumab discontinuation (median;111.5 days, IQR;95-555), no TMA recurrence was observed. In this analysis, eculizumab showed benefit in over half of this paediatric patient population. Ongoing clinical studies are expected to optimize the treatment regimen of terminal complement pathway inhibitor, and it may become a therapeutic option for paediatric HSCT-TMA in the future.

The treatment of atypical hemolytic uremic syndrome with eculizumab in pediatric patients: a systematic review

BACKGROUND

The atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy associated with high morbidity and high mortality. Eculizumab, a humanized anti-C5 monoclonal antibody, was the first medication approved for treating aHUS in 2011.

OBJECTIVE

The objective of this study is to evaluate the efficacy and safety of eculizumab treatment in pediatric patients with aHUS.

DATA SOURCES

We consulted PubMed, Scopus, SciELO, and Cochrane Library databases in July 2021. The descriptors were as follows: "Atypical Hemolytic Uremic Syndrome," "aHUS," "eculizumab," "Pediatrics," "Pediatric," "Child," "Children," "Adolescent."

STUDY ELIGIBILITY CRITERIA

The study eligibility criteria are as follows: clinical trials and observational studies that included pediatric patients with aHUS diagnosis and who were treated with eculizumab.

PARTICIPANTS AND INTERVENTIONS

The participants are pediatric patients, up to 18 years old, with aHUS. The intervention was eculizumab treatment.

STUDY APPRAISAL

For quality assessment, we used the Newcastle-Ottawa Scale, the National Institutes of Health (NIH) quality assessment tool for case series studies, and the Risk of Bias In Non-Randomized Studies of Interventions (ROBINS-I) tool.

RESULTS

The initial search retrieved 433 studies, from which 15 were selected after complete assessment: 9 cohorts, 4 case series, and 1 clinical trial. The publication date ranged from 2015 to 2021. In total, 940 pediatric patients were included, and 682 received eculizumab. All studies reported improvements in renal and hematological parameters in most of the patients treated with eculizumab. The mortality rate was 1.6% for all patients treated with eculizumab.

LIMITATIONS

The number of studies is limited, and the included studies were methodologically heterogeneous. The studies were mostly observational and many had small sample sizes.

CONCLUSIONS

Eculizumab appears to be safe and effective for the treatment of aHUS in pediatric patients. More research is necessary to establish long-term efficacy, safety, and time of discontinuation.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42021266255.

Thrombotic microangiopathy versus class IV lupus nephritis in systemic lupus erythematosus

BACKGROUND

Kidney involvement is common in patients with systemic lupus erythematosus (SLE). This study investigates the clinical and prognostic characteristics of thrombotic microangiopathy (TMA) compared to class IV lupus nephritis in SLE patients.

METHODS

A retrospective review of patients who underwent kidney biopsy, with a primary diagnosis of SLE and TMA between June 2006 and September 2018 was conducted. Those patients were subsequently compared to patients with class IV lupus nephritis between January 2018 and December 2018. Demographics, laboratory, and serological data at the time of biopsy were abstracted.

RESULTS

Among 214 SLE patients records screened, 27 were included in the final analysis. Eight patients had lupus-related TMA without evidence of active lupus nephritis, while 19 patients had class IV lupus nephritis without evidence of TMA. TMA patients had significantly higher lactate dehydrogenase levels (718 ± 499 vs. 264 ± 107.7 U/L, p = 0.009), serum C3 (100.6 ± 39.3 vs. 65.8 ± 27 mg/dL, p = 0.049), white blood cell count (14743.8 ± 7933.3 vs. 5807.9 ± 2053.2 × 10E3/uL, p < 0.001), and total bilirubin (0.8 ± 0.5 vs. 0.3 ± 0.1 mg/dL, p = 0.007) in addition to significantly lower platelet counts (158.4 ± 88.6 vs. 240.3 ± 100.3 × 10E3/uL, p = 0.03), and haptoglobin (68.8 ± 116.1 vs. 166.8 ± 95.4 mg/dL, p = 0.03). After a median follow-up time of 53 weeks, 3 patients with TMA were dialysis-dependent (37.5%), compared with none in class IV lupus nephritis patients (p = 0.002).

CONCLUSIONS

TMA-associated SLE has worse prognosis compared to class IV lupus nephritis. An array of laboratory and pathological findings may be of value in discriminating between those two entities.

The Inhibition of Complement System in Formal and Emerging Indications: Results from Parallel One-Stage Pairwise and Network Meta-Analyses of Clinical Trials and Real-Life Data Studies

This manuscript presents quantitative findings on the actual effectiveness of terminal complement component 5 (C5) inhibitors and complement component 1 (C1) esterase inhibitors through their formal and common “off-label” (compassionate) indications. The results emanated from pairwise and network meta-analyses to present evidence until September 2019. Clinical trials (CT) and real-life non-randomized studies of the effects of interventions (NRSI) are consistent on the benefits of C5 inhibitors and of the absence of effects of C1 esterase inhibitors (n = 7484): Mathematically, eculizumab (surface under the cumulative ranking area (SUCRA) >0.6) and ravulizumab (SUCRA ≥ 0.7) were similar in terms of their protective effect on hemolysis in paroxysmal nocturnal hemoglobinuria (PNH), thrombotic microangiopathy (TMA) in atypical hemolytic uremic syndrome (aHUS), and acute kidney injury (AKI) in aHUS, in comparison to pre-/off-treatment state and/or placebo (SUCRA < 0.01), and eculizumab was efficacious on thrombotic events in PNH (odds ratio (OR)/95% confidence interval (95% CI) in CT and real-life NRSI, 0.07/0.03 to 0.19, 0.24/0.17 to 0.33) and chronic kidney disease (CKD) occurrence/progression in PNH (0.31/0.10 to 0.97, 0.66/0.44 to 0.98). In addition, meta-analysis on clinical trials shows that eculizumab mitigates a refractory generalized myasthenia gravis (rgMG) crisis (0.29/0.13 to 0.61) and prevents new acute antibody-mediated rejection (AMR) episodes in kidney transplant recipients (0.25/0.13 to 0.49). The update of findings from this meta-analysis will be useful to promote a better use of complement inhibitors, and to achieve personalization of treatments with this class of drugs.

Pharmacology, Pharmacokinetics and Pharmacodynamics of Eculizumab, and Possibilities for an Individualized Approach to Eculizumab

Eculizumab is the first drug approved for the treatment of complement-mediated diseases, and current dosage schedules result in large interindividual drug concentrations. This review provides insight into the pharmacokinetic and pharmacodynamic properties of eculizumab, both for reported on-label (paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, generalized myasthenia gravis) and off-label (hematopoietic stem cell transplantation-associated thrombotic microangiopathy) indications. Furthermore, we discuss the potential of therapeutic drug monitoring to individualize treatment and reduce costs.

Prophylactic amoxicillin for the prevention of meningococcal infection in infants with atypical hemolytic uremic syndrome under treatment with eculizumab: a report of two cases

Eculizumab, a humanized monoclonal antibody to complement C5, is a therapeutic drug for atypical hemolytic-uremic syndrome (aHUS) that inhibits the terminal pathway of complement. Patients on eculizumab therapy may become more susceptible to infection with capsule-forming bacteria, including meningococci. Therefore, meningococcal vaccination is required for patients who are on eculizumab therapy. However, the means to prevent meningococcal infection in infants who cannot be vaccinated with the available meningococcal vaccine have not yet been established internationally. In two infants with aHUS at 4-5 months after birth, prophylactic oral amoxicillin was administered, and meningococcal infection was not detected during the period between the initiation of eculizumab therapy and the administration of meningococcal vaccine. Neither adverse events related to amoxicillin nor thrombotic microangiopathy occurred during the treatment. Thus, oral administration of amoxicillin may be effective for preventing meningococcal infection under treatment with eculizumab in infants who have not received meningococcal vaccination.

Pharmacokinetics and Pharmacodynamics Estimation of Eculizumab in a 2-Year-Old Girl With Atypical Hemolytic Uremic Syndrome: A Case Report With 4-Year Follow-Up

Background: Eculizumab has dramatically changed poor outcomes of complement-mediated atypical hemolytic uremic syndrome (aHUS) as first-line treatment. Discontinuation of eculizumab remains challenging, and doctor's visits every 2 weeks for intravenous injection because of standard dosing protocols is a huge burden. The Ultra-high cost of eculizumab is also an issue. We attempted to establish a personalized dosing regimen of eculizumab based on pharmacokinetics and pharmacodynamics in a 2-year-old girl with aHUS with a C3 mutation. Case presentation: She developed aHUS at 5 months of age and was successfully treated with eculizumab. At 2 years of age, we measured eculizumab concentrations and performed pharmacokinetics and pharmacodynamics analysis to optimize her dosing protocol. Her blood concentrations at every 2-, 3-, and 4-week intervals were simulated. Pharmacokinetics analysis showed that her eculizumab clearance was 40% lower than the population mean reported for aHUS. Pharmacokinetic simulation suggested that the 2- and 3-week interval regimen could be sufficient to achieve an efficient trough concentration (>100 μg/mL). We simulated her individual pharmacokinetics profile at 4 years of age with consideration of her growth, which still showed complete inhibition of the alternative complement pathway with the 3-week interval regimen. We continued the 300-mg eculizumab infusion every 3 weeks while CH50 levels were constantly maintained at undetectably low concentrations with no recurrence until 6 years of age. Conclusions: Pharmacokinetics and pharmacodynamics estimation was useful for establishing a personalized dosing regimen for eculizumab and reducing the patient's burden and high medical costs.

Treatment of hemolytic uremic syndrome related to Bordetella pertussis infection -is plasma exchange or eculizumab use necessary?

Background

Bordetella pertussis infection is a known trigger of atypical hemolytic uremic syndrome (HUS). For patients suspected of having atypical HUS, prompt plasma exchange/infusion (PE/PI) or eculizumab (ECZ) treatment is recommended.

Case presentation

We report a 1-month-old female infant who was admitted with a severe cough and a B. pertussis-positive sputum culture. She was born at 38 weeks gestation and did not have a family history of renal diseases. Hemophagocytic syndrome was suspected and she was transferred to our hospital 17 days after her initial admission. One day later, she developed acute kidney injury and was diagnosed with HUS triggered by B. pertussis infection. Her plasma complement levels were low and her kidney function continued to worsen over the next few days. However, prior to starting ECZ treatment, her kidney function improved spontaneously; she did not receive PE/PI or ECZ. She was discharged 46 days after her initial hospitalization, without complications. A genetic workup revealed no mutations in CFH, CFI, CFB, C3, MCP, THBD, or DGKE.

Conclusions

This case demonstrates that B. pertussis infection-related HUS may resolve spontaneously. The decision to treat during the acute phase is challenging because B. pertussis often affects infants suspected of having atypical HUS. However, ECZ may not be the first treatment option for patients with B. pertussis infection-related HUS unless they show an indicated genetic abnormality; if ECZ is used, early discontinuation should be considered.

Pathogenesis of Atypical Hemolytic Uremic Syndrome

Atypical hemolytic uremic syndrome (aHUS) is a type of thrombotic microangiopathy (TMA) defined by thrombocytopenia, microangiopathic hemolytic anemia, and renal failure. aHUS is caused by uncontrolled complement activation in the alternative pathway (AP). A variety of genetic defects in complement-related factors or acquired autoantibodies to the complement regulators have been found in 50 to 60% of all cases. Recently, however, the classification and diagnosis of aHUS are becoming more complicated. One reason for this is that some factors, which have not been regarded as complement-related factors, have been reported as predisposing factors for phenotypic aHUS. Given that genotype is highly correlated with the phenotype of aHUS, careful analysis of underlying genetic abnormalities or acquired factors is needed to predict the prognosis or to decide an optimal treatment for the disease. Another reason is that complement dysregulation in the AP have also been found in a part of other types of TMA such as transplantation-related TMA and pregnancy-related complication. Based on these findings, it is now time to redefine aHUS according to the genetic or acquired background of abnormalities.Here, we review the pathogeneses and the corresponding phenotypes of aHUS and complement-related TMAs.

Practical issues in using eculizumab for children with atypical haemolytic uraemic syndrome in the acute phase: A review of four patients

AIM

Recently eculizumab, a monoclonal antibody to C5, was found to improve the disease course of atypical haemolytic uraemic syndrome (aHUS) and has been recommended as the first line treatment by an international consensus guideline. However, several practical issues in the use of eculizumab for the acute phase of aHUS have yet to be resolved.

METHODS

Children who received eculizumab with diagnosis of aHUS between March 2010 and December 2015 at Tokyo Metropolitan Children's Medical Center were enrolled. aHUS was diagnosed according to the haemolytic uraemic syndrome (HUS) criteria after excluding Shiga toxin-inducing Escherichia coli (STEC) -associated HUS and thrombocytopaenic purpura. We retrieved and analyzed data from the electronic medical records at our institution.

RESULTS

We reviewed four patients with suspected aHUS. Eculizumab was discontinued in one patient in whom STEC-HUS was later diagnosed. Treatment was continued in the remaining three patients without recurrence. Practical issues included difficulty in diagnosing aHUS, particularly in the acute phase, risk of infection by encapsulated organisms, especially Neisseria meningitis, and infusion reaction. In addition to issues relating to the acute phase, discontinuing eculizumab in stable patients in the chronic phase must be considered.

CONCLUSION

Eculizumab, the first line treatment for children with aHUS, is usually effective. However, certain problems associated with its use require caution to be exercised. As clinical information on eculizumab are still very limited, and the rationale for its long-term use has yet to be established, physicians are advised to exercise care when using eculizumab to manage aHUS.

Safety and effectiveness of eculizumab for pediatric patients with atypical hemolytic-uremic syndrome in Japan: interim analysis of post-marketing surveillance

Background

In 2013, eculizumab was approved for treatment of the atypical hemolytic–uremic syndrome (aHUS) in Japan, which was defined as a thrombotic microangiopathy (TMA) excluding Shiga toxin-producing Escherichia coli-HUS and thrombotic thrombocytopenic purpura. Simultaneously, post-marketing surveillance was started to assess its safety and effectiveness. In 2016, Japanese clinical guide redefined terms to limit the use of “aHUS” to complement-mediated HUS only. Accordingly, TMA with other causes was defined as secondary TMA. Here we report the interim analysis of post-marketing surveillance of pediatric patients with aHUS and secondary TMA.

Methods

Pediatric patients treated with eculizumab from approval to 15 March 2017 were included in this observational real-world study. Clinical endpoints of effectiveness were TMA event–free status, complete TMA response, platelet count normalization, and improvement of estimated glomerular filtration rate (eGFR). Adverse reactions to eculizumab were also analyzed.

Results

In 27 pediatric patients with aHUS, median age at diagnosis was 4 years. Complement genes’ variants were detected in 14 of 21 patients (66.7%). Median time from diagnosis to eculizumab initiation was 2.0 days. TMA event–free status, complete TMA response, platelet normalization, and improvement in eGFR were achieved in 85.2, 36.4, 78.3, and 75.0% of patients, respectively. Three patients with aHUS died. Twenty-four and 10 adverse reactions were reported in 31 aHUS patients and 17 secondary TMA patients, respectively; however, no eculizumab-related death or meningococcal infection was reported.

Conclusions

This interim analysis confirmed that eculizumab is well-tolerated and effective for Japanese pediatric patients with aHUS in a real-world setting.

Electronic supplementary material

The online version of this article (10.1007/s10157-018-1610-2) contains supplementary material, which is available to authorized users.

Haemolytic uraemic syndrome

Haemolytic uraemic syndrome is a form of thrombotic microangiopathy affecting predominantly the kidney and characterised by a triad of thrombocytopenia, mechanical haemolytic anaemia, and acute kidney injury. The term encompasses several disorders: shiga toxin-induced and pneumococcus-induced haemolytic uraemic syndrome, haemolytic uraemic syndrome associated with complement dysregulation or mutation of diacylglycerol kinase ɛ, haemolytic uraemic syndrome related to cobalamin C defect, and haemolytic uraemic syndrome secondary to a heterogeneous group of causes (infections, drugs, cancer, and systemic diseases). In the past two decades, experimental, genetic, and clinical studies have helped to decipher the pathophysiology of these various forms of haemolytic uraemic syndrome and undoubtedly improved diagnostic approaches. Moreover, a specific mechanism-based treatment has been made available for patients affected by atypical haemolytic uraemic syndrome due to complement dysregulation. Such treatment is, however, still absent for several other disease types, including shiga toxin-induced haemolytic uraemic syndrome.

Clinical guides for atypical hemolytic uremic syndrome in Japan

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In 2013, we developed diagnostic criteria to enable early diagnosis and timely initiation of appropriate treatment for aHUS. Recent clinical and molecular findings have resulted in several proposed classifications and definitions of thrombotic microangiopathy and aHUS. Based on recent advances in this field and the emerging international consensus to exclude secondary TMAs from the definition of aHUS, we have redefined aHUS and proposed diagnostic algorithms, differential diagnosis, and therapeutic strategies for aHUS.

Two cases of atypical hemolytic uremic syndrome (aHUS) and eosinophilic granulomatosis with polyangiitis (EGPA): a possible relationship

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by hemolysis, thrombocytopenia, and renal failure. It is related to genetic mutations of the alternative complement pathway and is difficult to differentiate from other prothrombotic microangiopathies. Eosinophilic granulomatosis with polyangiitis (EGPA) (Churg-Strauss syndrome, CSS) is a systemic ANCA-associated vasculitis and a hypereosinophilic disorder where eosinophils seem to induce cell apoptosis and necrosis and therefore, vasculitis. Here, we report the case of two CSS patients with a genetic complement disorder consistent with aHUS diagnosis. Both patients showed histologic features that supported the diagnosis of CSS, and a genetic complement study confirmed the suspected aHUS diagnosis. In the case where eculizumab was administered, the global response was excellent. There is very limited understanding of the genetics and epidemiology of both, atypical HUS and EGPA, but considering our two patients we suggest that an etiopathogenic link exists among patients diagnosed with both entities.

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.

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.

Clinical guides for atypical hemolytic uremic syndrome in Japan

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In 2013, we developed diagnostic criteria to enable early diagnosis and timely initiation of appropriate treatment for aHUS. Recent clinical and molecular findings have resulted in several proposed classifications and definitions of thrombotic microangiopathy and aHUS. Based on recent advances in this field and the emerging international consensus to exclude secondary TMAs from the definition of aHUS, we have redefined aHUS and proposed diagnostic algorithms, differential diagnosis, and therapeutic strategies for aHUS.