A Significant Contribution of the Classical Pathway of Complement in SARS-CoV-2 Neutralization of Convalescent and Vaccinee Sera.

Although high titers of neutralizing Abs in human serum are associated with protection from reinfection by SARS-CoV-2, there is considerable heterogeneity in human serum-neutralizing Abs against SARS-CoV-2 during convalescence between individuals. Standard human serum live virus neutralization assays require inactivation of serum/plasma prior to testing. In this study, we report that the SARS-CoV-2 neutralization titers of human convalescent sera were relatively consistent across all disease states except for severe COVID-19, which yielded significantly higher neutralization titers. Furthermore, we show that heat inactivation of human serum significantly lowered neutralization activity in a live virus SARS-CoV-2 neutralization assay. Heat inactivation of human convalescent serum was shown to inactivate complement proteins, and the contribution of complement in SARS-CoV-2 neutralization was often >50% of the neutralizing activity of human sera without heat inactivation and could account for neutralizing activity when standard titers were zero after heat inactivation. This effect was also observed in COVID-19 vaccinees and could be abolished in individuals who were undergoing treatment with therapeutic anti-complement Abs. Complement activity was mainly dependent on the classical pathway with little contributions from mannose-binding lectin and alternative pathways. Our study demonstrates the importance of the complement pathway in significantly increasing viral neutralization activity against SARS-CoV-2 in spike seropositive individuals.

Use of Intravenous Albumin: A Guideline From the International Collaboration for Transfusion Medicine Guidelines.

BACKGROUND: Albumin is used commonly across a wide range of clinical settings to improve hemodynamics, to facilitate fluid removal, and to manage complications of cirrhosis. The International Collaboration for Transfusion Medicine Guidelines developed guidelines for the use of albumin in patients requiring critical care, undergoing cardiovascular surgery, undergoing kidney replacement therapy, or experiencing complications of cirrhosis. METHODS: Cochairs oversaw the guideline development process and the panel included researchers, clinicians, methodologists, and a patient representative. The evidence informing this guideline arises from a systematic review of randomized clinical trials and systematic reviews, in which multiple databases were searched (inception through November 23, 2022). The panel reviewed the data and formulated the guideline recommendations using Grading of Recommendations Assessment, Development and Evaluation methodology. The guidelines were revised after public consultation. RESULTS: The panel made 14 recommendations on albumin use in adult critical care (three recommendations), pediatric critical care (one recommendation), neonatal critical care (two recommendations), cardiovascular surgery (two recommendations), kidney replacement therapy (one recommendation), and complications of cirrhosis (five recommendations). Of the 14 recommendations, two recommendations had moderate certainty of evidence, five recommendations had low certainty of evidence, and seven recommendations had very low certainty of evidence. Two of the 14 recommendations suggested conditional use of albumin for patients with cirrhosis undergoing large-volume paracentesis or with spontaneous bacterial peritonitis. Twelve of 14 recommendations did not suggest albumin use in a wide variety of clinical situations where albumin commonly is transfused. CONCLUSIONS: Currently, few evidence-based indications support the routine use of albumin in clinical practice to improve patient outcomes. These guidelines provide clinicians with actionable recommendations on the use of albumin.

The operational impact of introducing cold stored platelets.

BACKGROUND: Cold stored platelets (CSP) undergo physical changes that make them better at initiating a clot. While cold stored platelets are superior for reducing bleeding in actively bleeding patients, room temperature platelets (RTP) are better for increasing platelet count in patients requiring a prophylactic transfusion. However, whether the overhead required to maintain a dual platelet inventory of both RTP and CSP could be compensated by reduced platelet wastage resulting from the longer shelf life of CSP has not been determined. STUDY DESIGN AND METHODS: A simulation model of a regional blood supply was built, with focus on the operations of a case hospital. Two scenarios were considered: "No-CSP," in which the hospital issues only RTP, and "CSP," in which the hospital issues both RTP and CSP Within the CSP scenario, conditions were tested under which the hospital receives only RTP and converts some to cold stored platelets and a second strategy where the hospital receives CSP from the regional supplier in addition to converting RTP. RESULTS: A centralized supply of CSP is necessary since on-site conversion is limited by platelet age. Product shortages decrease with increased CSP inventory, but CSP wastage increases. It was also determined that, because relatively few RTP units can be converted on-site, RTP wastage is not significantly decreased with the introduction of CSP. CONCLUSION: Given the clinical benefits for treatment of trauma, CSP is a desirable addition to a blood formulary. However, it is unlikely that significant reductions in RTP wastage will occur because of the introduction of CSP.

Red Blood Cell Transfusion: 2023 AABB International Guidelines.

Importance: Red blood cell transfusion is a common medical intervention with benefits and harms. Objective: To provide recommendations for use of red blood cell transfusion in adults and children. Evidence Review: Standards for trustworthy guidelines were followed, including using Grading of Recommendations Assessment, Development and Evaluation methods, managing conflicts of interest, and making values and preferences explicit. Evidence from systematic reviews of randomized controlled trials was reviewed. Findings: For adults, 45 randomized controlled trials with 20 599 participants compared restrictive hemoglobin-based transfusion thresholds, typically 7 to 8 g/dL, with liberal transfusion thresholds of 9 to 10 g/dL. For pediatric patients, 7 randomized controlled trials with 2730 participants compared a variety of restrictive and liberal transfusion thresholds. For most patient populations, results provided moderate quality evidence that restrictive transfusion thresholds did not adversely affect patient-important outcomes. Recommendation 1: for hospitalized adult patients who are hemodynamically stable, the international panel recommends a restrictive transfusion strategy considering transfusion when the hemoglobin concentration is less than 7 g/dL (strong recommendation, moderate certainty evidence). In accordance with the restrictive strategy threshold used in most trials, clinicians may choose a threshold of 7.5 g/dL for patients undergoing cardiac surgery and 8 g/dL for those undergoing orthopedic surgery or those with preexisting cardiovascular disease. Recommendation 2: for hospitalized adult patients with hematologic and oncologic disorders, the panel suggests a restrictive transfusion strategy considering transfusion when the hemoglobin concentration is less than 7 g/dL (conditional recommendations, low certainty evidence). Recommendation 3: for critically ill children and those at risk of critical illness who are hemodynamically stable and without a hemoglobinopathy, cyanotic cardiac condition, or severe hypoxemia, the international panel recommends a restrictive transfusion strategy considering transfusion when the hemoglobin concentration is less than 7 g/dL (strong recommendation, moderate certainty evidence). Recommendation 4: for hemodynamically stable children with congenital heart disease, the international panel suggests a transfusion threshold that is based on the cardiac abnormality and stage of surgical repair: 7 g/dL (biventricular repair), 9 g/dL (single-ventricle palliation), or 7 to 9 g/dL (uncorrected congenital heart disease) (conditional recommendation, low certainty evidence). Conclusions and Relevance: It is good practice to consider overall clinical context and alternative therapies to transfusion when making transfusion decisions about an individual patient.

Transfusion medicine education delivery in Rwanda: Adapting Transfusion Camp to a resource-limited setting.

BACKGROUND: Due to few teaching faculty, resource-limited settings may lack the education curricula providers need for safe practice. As safe surgery becomes an increasing priority worldwide, it is essential to improve access to critical education content including in transfusion medicine. Transfusion Camp is a longitudinal curriculum, shown to increase knowledge in postgraduate trainees. The objective was to develop a sustainable bilateral partnership between Rwanda and Canada, and to integrate Transfusion Camp into the existing curriculum of the School of Medicine and Pharmacy at University of Rwanda. METHODS: A Transfusion Camp pilot course was initiated through collaboration of experts in Rwanda and Canada. Planning occurred over 6 months via online and in-person meetings. Canadian teaching faculty adapted course content via iterative discussion with Rwandan faculty. Final content was delivered through online pre-recorded lectures by Canadian Faculty, and in-person small-group seminars by Rwandan Faculty. Project feasibility was assessed through structured evaluation and informal debriefing. RESULTS: Twenty-seven postgraduate trainees were present for the pilot course, of whom 21 (78%) submitted evaluation forms. While the structure and content of the adapted Transfusion Camp curriculum were well-received, the majority of respondents indicated a preference for in-person rather than pre-recorded lectures. Debriefing determined that future courses should focus on continuing education initiatives aimed at physicians entering or already in independent practice. CONCLUSION: A partnership between universities and blood operators in high-resource and resource-limited countries results in a transfusion medicine curriculum that is locally applicable, multidisciplinary, and supportive of learning benefitting the learners and educators alike.

Including the patient in patient blood management: Development and assessment of an educational animation tool.

BACKGROUND: Patient blood management (PBM) programs are effective at reducing transfusion-associated mortality and morbidity; however, patient engagement within the realm of PBM remains relatively unstudied. Our objectives were to develop a novel educational tool utilizing animation to educate preoperative patients about anemia and to evaluate the effectiveness of this intervention. STUDY DESIGN AND METHODS: We created a patient-facing animation for preoperative surgical patients. The animation addressed characters' health journeys from diagnosis to treatment, addressing the role of PBM. We utilized the concept of patient activation as a means to empower patients, and developed the animation to be as accessible as possible. Post-viewing, patients provided feedback utilizing an electronic survey. RESULTS: A final version of the animation can be found here: https://vimeo.com/495857315. A total of 51 participants viewed our animation, the majority of whom were planned to undergo joint replacement or cardiac surgery. Almost all (94%, N = 4) agreed that taking an active role in their health was the most important factor in determining their ability to function. The video was felt to be easy to understand (96%, N = 49), and 92% (N = 47) agreed that they had a better understanding of anemia and its treatment. After watching the animation, patients felt more certain that they could follow through with their PBM plan (98%, N = 50). DISCUSSION: To the best of our knowledge, there are no other PBM-specific patient education animations. Patients enjoyed learning about PBM though animation, and patient education may lead to better uptake of PBM interventions. We hope that other hospitals will be inspired to pursue this approach.

Development of a national out-of-hospital transfusion protocol: a modified RAND Delphi study.

BACKGROUND: Early resuscitation with blood components or products is emerging as best practice in selected patients with trauma and medical patients; as a result, out-of-hospital transfusion (OHT) programs are being developed based on limited and often conflicting evidence. This study aimed to provide guidance to Canadian critical care transport organizations on the development of OHT protocols. METHODS: The study period was July 2021 to June 2022. We used a modified RAND Delphi process to achieve consensus on statements created by the study team guiding various aspects of OHT in the context of critical care transport. Purposive sampling ensured representative distribution of participants in regard to geography and relevant clinical specialties. We conducted 2 written survey Delphi rounds, followed by a virtual panel discussion (round 3). Consensus was defined as a median score of at least 6 on a Likert scale ranging from 1 ("Definitely should not include") to 7 ("Definitely should include"). Statements that did not achieve consensus in the first 2 rounds were discussed and voted on during the panel discussion. RESULTS: Seventeen subject experts participated in the study, all of whom completed the 3 Delphi rounds. After the study process was completed, a total of 39 statements were agreed on, covering the following domains: general oversight and clinical governance, storage and transport of blood components and products, initiation of OHT, types of blood components and products, delivery and monitoring of OHT, indications for and use of hemostatic adjuncts, and resuscitation targets of OHT. INTERPRETATION: This expert consensus document provides guidance on OHT best practices. The consensus statements should support efficient and safe OHT in national and international critical care transport programs.

Patient blood management in adults and children: What have we achieved, and what still needs to be addressed?

An overview of Patient Blood Management (PBM), with its main scope to preserve the patient's own blood to improve the patient's outcome, is presented here, including the research gaps that needs to be addressed, particularly in the pediatric age group. Next, novel techniques to analyse PBM data and the challenges and strategies of PBM implementation will also be discussed.

Transfusion camp: A retrospective study of self-reported impact on postgraduate trainee transfusion practice.

BACKGROUND: The optimal method of postgraduate transfusion medicine (TM) education remains understudied. One novel approach is Transfusion Camp, a longitudinal 5-day program that delivers TM education to Canadian and international trainees. The purpose of this study was to determine the self-reported impact of Transfusion Camp on trainee clinical practice. STUDY DESIGN AND METHODS: A retrospective analysis of anonymous survey evaluations from Transfusion Camp trainees over three academic years (2018-2021) was conducted. Trainees were asked, "Have you applied any of your learning from Transfusion Camp into your clinical practice?". Through an iterative process, responses were categorized into topics according to program learning objectives. The primary outcome was the rate of self-reported impact of Transfusion Camp on clinical practice. Secondary outcomes were to determine impact based on specialty and postgraduate year (PGY). RESULTS: Survey response rate was 22%-32% over three academic years. Of 757 survey responses, 68% of respondents indicated that Transfusion Camp had an impact on their practice, increasing to 83% on day 5. The most frequent areas of impact included transfusion indications (45%) and transfusion risk management (27%). Impact increased as PGY increased with 75% of PGY-4+ trainees reporting impact. In multivariable analysis, the impact of specialty and PGY varied depending on the objective. DISCUSSION: The majority of trainees report applying learnings from Transfusion Camp to their clinical practice with variations based on PGY and specialty. These findings support Transfusion Camp as an effective means of TM education and help identify high-yield areas and gaps for future curriculum planning.

Management of immune thrombotic thrombocytopenic purpura with caplacizumab: a Canadian, single-centre, real-world experience.

When combined with therapeutic plasma exchange (TPE) and immunosuppression, upfront universal administration of caplacizumab was shown to be effective in the management of immune thrombotic thrombocytopenic purpura (iTTP). However, access to this drug remains challenging in many jurisdictions. We retrospectively review results of a single-institution experience with caplacizumab over a 3-year period. During the study period, we treated 48 patients with iTTP, of which 11 (23%) received caplacizumab. Eight of these 11 patients (73%) were female; the median age was 45 years (IQR 37.0-58.5). All received TPE within 24 h of admission (median 9 exchanges, IQR 7.0-12.5), and high-dose steroids. Caplacizumab was initiated for a median of 6 days after admission (IQR 2.5-8.0) and continued for a median of 26 days (IQR 14.0-33.0). Five patients (45%) had refractory disease at caplacizumab initiation. Ten patients (91%) survived, reaching clinical remission. Platelet normalization was reached with a median of 4 days following caplacizumab initiation (IQR 1.5-4.0). Complications included minor bleeding (n = 1) and local allergic reaction (n = 1). No patients experienced TTP exacerbation; relapse occurred in two patients (18%) over 1-5 years of follow-up. Caplacizumab appeared to be effective and safe, despite delayed initiation and in the setting of refractory disease.

Immune thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening blood condition characterized by low platelets, anemia, and formation of blood clots in the small blood vessels. The condition results from a patient's immune system attacking a blood protein called ADAMTS13. The standard treatment for iTTP is plasma exchange (which replaces ADAMTS13) and medications, which suppress the immune system. Recently, a new medication, caplacizumab, has been shown to improve outcomes in iTTP, if combined with a standard treatment. However, this drug is expensive, and not readily available in all parts of the world, including Canada. In this article, we present the first Canadian experience with caplacizumab. Due to its limited access, the drug is frequently used in patients who are refractory to standard treatment or presented with severe organ damage. This contrasts with previously published studies, where it has been used upfront and in all patients with TTP. We find that caplacizumab may be safe and effective in this setting, demonstrating a low mortality rate and rapid recovery in most patients. While upfront and universal use of caplacizumab in the treatment of iTTP is optimal, our approach could be used in settings, where access to this medication is restricted.

In vitro characterization of a novel Arg102 mutation in the ADAMTS13 metalloprotease domain.

BACKGROUND: Congenital thrombotic thrombocytopenic purpura is caused by defects in the ADAMTS13 gene. ADAMTS13 is normally preactivated by conformational changes of the Metalloprotease (M) domain. Studying a novel congenital thrombotic thrombocytopenic purpura p.R102S mutation in the M domain, which results in undetectable ADAMTS13 activity in the patient, could help to explain the patients' phenotype and to elucidate the currently unclear mechanism of allosteric preactivation. OBJECTIVES: To investigate the in vitro effect of p.R102S mutation on ADAMTS13 secretion, activity, and allosteric preactivation. METHODS: Molecular modeling was used to study the effect of the mutation on the stability of ADAMTS13. Recombinant mutant ADAMTS13 was generated by transient and stable transfection of, respectively, CHO K1 and HEK293-T cells. ADAMTS13 antigen was measured in enzyme-linked immunosorbent assay. ADAMTS13 activity was measured in a FRETS-VWF73 assay. Allosteric preactivation was assessed in FRETS-VWF73 assay, using monoclonal antibody (mAb) 17G2 that normally induces a ∼2-fold increase in activity, and in enzyme-linked immunosorbent assay using mAb 6A6 recognizing a cryptic epitope in the M domain that becomes exposed after binding of 17G2. RESULTS: p.R102S mutation destabilizes the interactions between the M and Disintegrin-like (D) domain. p.R102S mutant secretion was impaired (35% of wild type) and activity was severely reduced (12% of wild type). p.R102S mutant could still be activated and the cryptic epitope of 6A6 was still fully exposed by 17G2 addition. CONCLUSION: p.R102S mutation destabilizes the M-D domain interactions, causing impaired ADAMTS13 secretion and activity, which explains the patients' phenotype. Allosteric preactivation of ADAMTS13 remains conserved in the presence of the p.R102S mutation.

Massive Hemorrhage Protocol: A Practical Approach to the Bleeding Trauma Patient.

Damage-control resuscitation is the standard of care for the hemorrhaging trauma patient. This approach combines rapid hemostasis and early-ratio-based blood product administration. These patients often require initiation of a massive hemorrhage protocol to support the systematic and coordinated delivery of care during this critical phase of resuscitation. Emerging evidence supports that this includes more than blood product administration alone but rather a comprehensive suite of treatments. In this article, we review the existing evidence and provide a pragmatic framework, the 7 Ts of massive hemorrhage protocol, to guide the care of patients with life-threatening traumatic hemorrhage.

Long-term follow-up of patients treated with caplacizumab and safety and efficacy of repeat caplacizumab use: Post-HERCULES study.

INTRODUCTION: Caplacizumab demonstrated efficacy and safety in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP) in the phase 3 HERCULES trial. However, data on long-term outcomes following caplacizumab treatment are limited. OBJECTIVES: The post-HERCULES trial (NCT02878603) evaluated long-term outcomes of patients with iTTP treated with caplacizumab in HERCULES and safety and efficacy of repeated caplacizumab use. PATIENTS/METHODS: Over 3 years of follow-up, patients could receive open-label caplacizumab with therapeutic plasma exchange (TPE) and immunosuppressive therapy (IST) in case of recurrence. Adverse events (AEs) were assessed during the overall study period (intention-to-observe [ITO] population) and during recurrences (recurrence population). TTP-related events (TTP-related death, recurrence, major thromboembolic events) were assessed in the efficacy ITO population (patients without recurrence during HERCULES or before post-HERCULES). RESULTS: Among 104 enrolled patients, incidences of AEs and serious AEs were similar between patients who had received caplacizumab + TPE + IST during HERCULES (n = 75) and those treated with placebo + TPE + IST (placebo; n = 29). TTP-related events occurred in 8% of patients (4/49) randomized to caplacizumab during HERCULES versus 38% (11/29) randomized to placebo. Nineteen patients had ≥1 recurrence; 13 of these were treated with caplacizumab. The first recurrence episode was resolved or resolving for all patients treated with caplacizumab, including nine patients with repeat caplacizumab use. All second recurrences (6/6) were resolved. Safety profile of caplacizumab for treatment of recurrence was consistent with HERCULES; most bleeding events were nonserious. No major cases of organ dysfunction were observed. CONCLUSIONS: Long-term follow-up supports the safety and efficacy of caplacizumab for iTTP and its repeated use for recurrences.

ONTraC: A 20-Year History of a Successfully Coordinated Provincewide Patient Blood Management Program: Lessons Learned and Goals Achieved.

Our understanding of the risks associated with perioperative anemia and transfusion, in terms of increased morbidity and mortality, has evolved over the past 2 decades. By contrast, our understanding of the potential mechanisms of injury and optimal treatment strategies remains incomplete. As such, the important role of effective patient blood management (PBM) programs, which address both the effective treatment of anemia and minimizes the need for red blood cell (RBC) transfusion, is of central importance to optimizing patient care and improving patient outcomes. We report on important clinical outcomes of the Ontario Transfusion Coordinator (ONTraC Program), a network of 25 hospital sites, working in coordination over the past 20 years. Transfusion nurse coordinators were assigned to apply multimodal best practice in PBM (including recommended changes in surgical approach; diagnosis, assessment, and treatment of anemia; and adherence to more restrictive RBC transfusion thresholds). Data were collected on various clinical parameters. We further described lessons learned and difficulties encountered in this multisite PBM initiative. A significant reduction in RBC transfusions was observed for numerous indexed surgeries. For example, RBC transfusion rates for knee arthroplasty decreased from 25% in 2002 to 0.4% in 2020. For coronary artery bypass graft (CABG) surgery, transfusion rates decreased from 60% in 2002 to 27% in 2020. We also observed a decrease in RBC units utilized per transfused patient for knee (2.1 ± 0.5 [2002] vs 1.0 ± 0.6 [2020] units per patient) and CABG surgery (3.3 ± 0.6 [2002] vs 2.3 ± 1.9 [2020] units per patient). These reductions were associated with favorable clinical outcomes, including reduced length of hospital stay (P = .00003) and a reduced rate of perioperative infections (P < .001) for nontransfused versus transfused patients. These advances have been achieved with estimated savings in the tens of millions of dollars annually. Our experience and data support the hypothesis that instituting an integrated network of transfusion nurse coordinators can provide an effective provincewide PBM program, reduce RBC transfusions, improve some patient outcomes, and reduce health care costs, as an example of a "win-win-win" medical program.

Relapse of immune thrombotic thrombocytopenic purpura (iTTP) possibly triggered by COVID-19 vaccination and/or concurrent COVID-19 infection.

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease that may be triggered by inflammation, including infection or vaccination. Since the start of the COVID-19 pandemic, several case reports were published on de novo or relapsed immune TTP (iTTP) in COVID-19-infected patients. Case reports of iTTP episodes following vaccination against COVID-19 are also emerging. We report a case of relapsed iTTP in a patient who received Moderna mRNA-1273 SARS-CoV-2 vaccine and developed concurrent severe COVID-19 infection. The patient's iTTP was successfully managed with caplacizumab, therapeutic plasma exchange and high-dose steroids. We summarise published cases of iTTP associated with COVID-19 infection or vaccination.

Complement-Amplifying Conditions in Atypical Hemolytic Uremic Syndrome: A Canadian Case Series.

Rationale: Thrombotic microangiopathies (TMAs) are systemic disorders that often affect the kidneys and encompass a heterogeneous group of conditions, including atypical hemolytic uremic syndrome (aHUS). The complement pathway is thought to play a crucial role in the pathogenesis of aHUS, and a favorable response can be obtained through complement C5 inhibition. There is emerging evidence to suggest that the same is also true for several other forms of TMA. Objective: The purpose of this series is to report cases of aHUS in which both an innate defect of the alternative complement pathway and a complement-amplifying condition were suspected. Methods: This case series describes 8 patients who were managed in Canadian tertiary centers for aHUS and who presented initially with complement-amplifying conditions. Results: In all cases, aHUS was associated with organ dysfunction and in some, with an innate defect of the alternative complement pathway. The complement-amplifying conditions identified were diverse including immune disorders, pregnancy, and a Shiga toxin infection. Patients improved rapidly when treated with eculizumab or plasma exchange. Conclusions: These observations illustrate the seriousness of secondary aHUS. They also add to existing lines of evidence that the complement pathway is potentially involved in this condition and that it should be considered as a therapeutic target of interest under such circumstances.

Justification: Les microangiopathies thrombotiques (MAT) sont des troubles systémiques qui affectent souvent les reins et qui englobent un groupe hétérogène d'affections, notamment le syndrome hémolytique et urémique atypique (SHUa). On pense que la voie du complément joue un rôle crucial dans la pathogenèse du SHUa et qu'une réponse favorable pourrait être obtenue par inhibition du complément C5. De nouvelles preuves suggèrent qu'il en serait de même pour plusieurs autres formes de MAT. Objectif: Cette série vise à rapporter des cas de SHUa pour lesquels on soupçonnait à la fois une anomalie congénitale de la voie alterne du complément et une condition d'amplification du complément. Méthodologie: Cette série décrit les cas de huit patients qui présentaient initialement des conditions d'amplification du complément et qui ont été pris en charge pour un SHUa dans des centres tertiaires canadiens. Résultats: Dans tous les cas, le SHUa était associé à un dysfonctionnement d'organe et, dans certains cas, à une anomalie congénitale de la voie alterne du complément. Les conditions d'amplification du complément identifiées étaient diverses, notamment des troubles immunitaires, une grossesse et une infection à une shigatoxine. L'état des patients s'est rapidement amélioré après un traitement avec éculizumab ou des échanges plasmatiques. Conclusion: Ces observations illustrent la gravité du SHUa secondaire. Elles s'ajoutent aux preuves existantes qui suggèrent que la voie du complément est potentiellement impliquée dans cette pathologie et qu'elle devrait être considérée comme une cible thérapeutique d'intérêt dans de telles circonstances.