Brief report: induction of sustained remission in recurrent catastrophic antiphospholipid syndrome via inhibition of terminal complement with eculizumab

Antiphospholipid syndrome in children

Antiphospholipid syndrome (APS) in children is a rare disease associated with significant morbidity and mortality. In comparison with APS in adults, pediatric APS has a more severe presentation with frequent recurrences of thrombotic events and a higher probability of life-threatening catastrophic APS. Nonthrombotic manifestations are also more common in the pediatric age group and can precede thrombosis. New classification criteria have been introduced recently and have not yet been assessed in pediatric patients with APS. In addition to anticoagulation drugs, other novel therapies have emerged including the use of B cell and complement inhibitors, especially in catastrophic APS. The purpose of this review is to provide a broad overview of aPL-related clinical manifestations in pediatric patients based on the analysis of published cohorts and data from the international pediatric APS registry. We also aim to illustrate APS in infants caused by transplacentally transferred maternal aPL, which is very rarely associated with acute thrombotic events in the perinatal period and more frequently with long-term neurodevelopmental abnormalities.

Management of Cardiovascular Complications in Antiphospholipid Syndrome: A Narrative Review with a Focus on Older Adults

Antiphospholipid syndrome (APS), also known as Hughes syndrome, is an acquired autoimmune and procoagulant condition that predisposes individuals to recurrent thrombotic events and obstetric complications. Central is the role of three types of antiphospholipid antibodies that target phospholipid-binding proteins: lupus anticoagulant (LAC), anti-β2-glycoprotein I (β2-GPI-Ab), and anti-cardiolipin (aCL). Together with clinical data, these antibodies are the diagnostic standard. However, the diagnosis of APS in older adults may be challenging and, in the diagnostic workup of thromboembolic complications, it is an underestimated etiology. The therapeutic management of APS requires distinguishing two groups with differential risks of thromboembolic complications. The standard therapy is based on low-dose aspirin in the low-risk group and vitamin K antagonists in the high-risk group. The value of direct oral anticoagulants is currently controversial. The potential role of monoclonal antibodies is investigated. For example, rituximab is currently recommended in catastrophic antiphospholipid antibody syndrome. Research is ongoing on other monoclonal antibodies, such as daratumumab and obinutuzumab. This narrative review illustrates the pathophysiological mechanisms of APS, with a particular emphasis on cardiovascular complications and their impact in older adults. This article also highlights advancements in the diagnosis, risk stratification, and management of APS.

Systemic lupus erythematosus presenting with atypical hemolytic uremic syndrome: a case report and review of the literature

Systemic lupus erythematosus (SLE) can present with a diverse array of hematologic manifestations, among which atypical hemolytic uremic syndrome (aHUS) is a rare entity. SLE-triggered aHUS has significant morbidity and mortality without timely intervention, yet its frequency remains uncertain and optimal strategies for complement-directed therapies are largely expert-driven. We performed a comprehensive literature review and present a case of a 23-year-old female newly diagnosed with SLE/class IV lupus nephritis who developed aHUS that rapidly responded to the C5 antagonist, eculizumab. Review of the current literature identified forty-nine published cases of SLE with concurrent aHUS and revealed a predilection for aHUS in younger SLE patients, concurrent presentation with lupus nephritis, anti-dsDNA positivity, and complement system abnormalities. Over seventy percent of cases used eculizumab as complement-directed therapy with a trend towards faster time to improvement in laboratory parameters, though reported outcomes were highly variable. Early recognition of aHUS in SLE is pivotal in guiding appropriate therapeutic interventions, and prompt initiation of eculizumab may reduce the potential morbidity associated with plasmapheresis and additional immunosuppression. While eculizumab showcases promising results, its optimal timing and duration remain elusive. An understanding of a patients' complement genetics could aid management strategies, and ongoing research into complement-targeted therapies offers promising avenues for both SLE and aHUS treatment.

Diagnosis and Management of Catastrophic Antiphospholipid Syndrome and the Potential Impact of the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria

Catastrophic antiphospholipid syndrome (CAPS) is a rare and life-threatening condition characterized by the persistence of antiphospholipid antibodies and occurrence of multiple vascular occlusive events. CAPS currently remains a diagnostic challenge and requires urgent treatment. The diagnosis of CAPS is made difficult by classification criteria used as diagnostic criteria in clinical practice, knowledge derived from retrospective data and case reports, confounding clinical and biological features, and its rapid onset and mortality. The absence of prospective studies of CAPS limits the strength of evidence for guideline treatment protocols. This comprehensive review summarizes the current understanding of the disease, and discusses how the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria impact the definition and therapeutic management of CAPS, which is considered the most severe form of APS. The correct integration of 2023 ACR/EULAR APS classification criteria is poised to facilitate CAPS diagnosis, particularly in critical situations, offering a promising avenue for improved outcomes.

Antiphospholipid syndrome pathogenesis in 2023: an update of new mechanisms or just a reconsideration of the old ones?

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (β2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). β2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating β2GPI tissue presentation. β2GPI/β2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

Antiphospholipid Syndrome and Kidney Involvement

BACKGROUND

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by the development of autoantibodies and the impairment of the coagulation system. Knowledge about this syndrome is increasing over time, but kidney involvement, especially APS nephropathy, still represents a challenge for physicians.

SUMMARY

A "two hit" model has been hypothesized to explain APS pathophysiology, and the role played by some factors, such as the complement system, is becoming more and more clear. From a clinical point of view, along with thrombosis in any site and/or obstetric morbidities, that are the hallmarks of APS, a constellation of several other clinical symptoms is related to APS. These symptoms alone are not sufficient to fulfill Sydney criteria for APS and this could potentially lead to omitting some diagnoses. The mainstay of management of APS is antithrombotic therapy, but there are expectations for new drugs that regulate the immune system. APS could affect the kidneys in many ways and among them, APS nephropathy is an intriguing entity that has been overlooked in recent years. Novel studies on APS nephropathy are lacking.

KEY MESSAGES

In this review, we discuss what we currently know about APS and its relationship with the kidney, with an eye toward the future perspectives. Multicenter studies on APS nephropathy are necessary in order to develop targeted therapies.

An update on the biologics for the treatment of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and pregnancy morbidity with the persistent presence of antiphospholipid antibodies (aPLs). Although anticoagulation is the primary treatment for APS, it fails in approximately 20-30% of obstetric APS cases and more than 30% of thrombotic APS cases. Therefore, there is a need for new, targeted treatments beyond anticoagulants. Biologics, such as rituximab and eculizumab, have been recommended for refractory catastrophic APS. This review focuses on the recent advancements in the pathogenesis of APS and explores the potential of targeted treatments, including eculizumab, rituximab, belimumab, daratumumab, obinutuzumab, and anti-TNF-α antibodies, for APS management.

Therapeutische Aspekte beim Antiphospholipidsyndrom

Das Antiphospholipidsyndrom (APS) wird klinisch durch venöse oder arterielle Thrombosen sowie Schwangerschaftskomplikationen gekennzeichnet und serologisch durch den Nachweis von Antiphospholipidantikörpern (aPL) bzw. eines Lupusantikoagulans (LA). In den letzten Jahren wurde evident, dass insbesondere bei Vorliegen aller drei serologischen Kriterien, Antikörper gegen Cardiolipin (aCL), gegen ß2-Glykoprotein-1 (aß2-GP1) und ein positives Lupusantikoagulans, die sog. Triple-Positivität, das Risiko für (weitere) thromboembolische und geburtshilfliche Komplikationen deutlich erhöht ist. Therapeutisch werden Thrombozytenaggregationshemmer (ASS), Heparin und Vitamin K Antagonisten eingesetzt. Von der Verwendung direkter oraler Antikoagulantien beim APS wird abgeraten. Eine Immunsuppression ist für die Vermeidung weiterer thromboembolischer Komplikationen eines APS nicht wirksam.

Emerging Therapies in Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is the most common cause of acquired immune-mediated thrombophilia. This syndrome is broadly defined by the presence of arterial or venous thrombosis, or pregnancy morbidity, in the presence of high levels of antiphospholipid antibodies. Despite recognition of this disorder more than 50 years ago, a fundamental unifying pathogenesis has not been determined. Due to this, mechanism-based therapies for APS are not available, and current management following thrombotic events suggests anticoagulation of indeterminate duration, or for obstetric complications, heparin/low molecular weight heparin and aspirin. However, APS is an autoimmune disorder, and several approaches focused on modulating the immune response or its effectors have been employed. Those which have been most extensively studied include hydroxychloroquine, rituximab and eculizumab, an inhibitor of complement C5. In this report, we review in depth, and critique, key clinical studies of these agents. Since all of these studies are small, our conclusions are qualified. However, it appears that hydroxychloroquine may enhance the anticoagulant efficacy of vitamin K antagonists in APS patients, and that rituximab may ameliorate some of the "non-criteria" manifestations of APS. The catastrophic antiphospholipid syndrome (CAPS) is associated with diffuse thrombosis, multi-organ dysfunction, and ∼30% mortality. A high incidence of complement regulatory gene mutations, and compelling data concerning the efficacy of eculizumab in CAPS, suggests an important role for complement in this disorder. However, additional work is needed to clarify the role of complement in non-catastrophic APS, though emerging data suggests that complement inhibition may be effective in preventing thrombosis in these patients as well.

Exploring the risk factors for ischemic cerebrovascular disease in systemic lupus erythematosus: A single-center case-control study

Objectives

Ischemic cerebrovascular disease (ICVD) is one of the most common and severe complications in systemic lupus erythematosus (SLE). We aim to explore the risk factors for ICVD in SLE and to assess their associated clinical characteristics.

Methods

In this study, 44 lupus patients with ICVD (ICVD-SLE) and 80 age- and sex-matched lupus patients without ICVD (non-ICVD-SLE) who were hospitalized in our center between 2014 and 2021 were enrolled. A comprehensive set of clinical and socio-demographic data was recorded. In the ICVD-SLE group, the modified Rankin score (mRS) at 90 days after the occurrence of ICVD, the brain MRI, and arterial ultrasonography findings were collected. Group comparisons were made with continuous variables using an independent t-test or the Mann–Whitney test, and with categorical variables using the chi-square test or Fisher exact test. Multivariate logistic regression analysis was performed to identify the risk factors for ICVD in SLE. Patients with ICVD-SLE were divided into three subgroups according to the gradations of intracranial arterial stenosis (ICAS). The subgroup comparisons were performed by one-way ANOVA test or Kruskal–Wallis test.

Results

Of the 44 patients with ICVD, 45% had a large-vessel ischemic stroke, 50% had a symptomatic lacunar stroke, and 9% had a transient ischemic attack. 2 (4.5%) had both large-vessel ischemic stroke and symptomatic lacunar stroke. Multivariate logistic regression analysis showed that cutaneous vasculitis (OR=7.36, 95% CI=2.11–25.65), anticardiolipin antibody (aCL) (OR=4.38, 95% CI=1.435–13.350), and lupus anticoagulant (LA) (OR=7.543,95% CI=1.789–31.808) were the risk factors, and hydroxychloroquine (HCQ) therapy (OR=0.198, 95% CI=0.078–0.502) was the protective factor, after controlling for confounders. During the analysis of the subgroups, no significant difference was observed between the patients in the group without internal carotid arterial occlusion (ICAS) and those with severe ICAS except for diagnostic delay. However, patients in the moderate ICAS group were older when SLE occurred (P<0.01), had a longer diagnostic delay (P<0.01), a lower percentage of hypocomplementemia (P=0.05) and steroids and HCQ therapy (P=0.01, P=0.05, respectively), a trend toward lower mRS score, but a higher incidence of carotid atherosclerotic plaque (P<0.01), when compared with the other two subgroups.

Conclusion

Cutaneous vasculitis and antiphospholipid antibodies (aPLs) are associated with an increased risk of ICVD, while HCQ therapy may provide protection against ICVD in SLE. The ICVD in younger lupus patients is associated with complement-mediated inflammation and poorer outcome, and require immunosuppressive therapy, whereas the ICVD in elderly patients are characterized by moderate ICAS and carotid atherosclerotic plaques.

Cardiovascular complications of catastrophic antiphospholipid syndrome: a case report and review of literature

Background

Antiphospholipid syndrome (APS) is an autoimmune response characterized clinically by arterial or venous thrombosis. One of the rare and series forms of APS is the catastrophic APS (CAPS). The incidence of CAPS has been reported in 0.8% of patients with APS. There have been very few case reports with cardiac involvement in CAPS. Common cardiac manifestations include valvular thickening and lesions, coronary artery disease, and myocardial infarction due to microvascular thrombosis. Here, we are reporting a case of CAPS associated with heart failure and a literature review of similar cases.

Case summary

A 24-year-old woman with a history of APS presented with shortness of breath and right-sided pleuritic chest pain. Computed tomography pulmonary angiogram revealed new pulmonary emboli in the right lung. After 5 days, she developed high-grade fever with negative infectious workup, acute hypoxic respiratory failure with pulmonary oedema, shock, acute kidney injury, and transthoracic echocardiography showed reduced ejection fraction and global hypokinesia. The constellation of multi-organ failure, symptoms within a week, the presence of antiphospholipid antibodies, and exclusion of other causes, CAPS was diagnosed. The patient showed significant improvement with pulse steroids, IV plasmapheresis and got discharged on oral prednisone taper and anticoagulation with home health.

Conclusion

There are different cardiac complications associated with CAPS, including congestive heart failure, acute coronary syndrome, valvular lesions, and thrombus. Heart failure management in CAPS includes triple therapy of intravenous immune globulin, IV plasmapheresis, and corticosteroids rather than conventional treatment.

The complement system and autoimmune diseases

The complement system plays a key role in the pathogenesis of autoimmune diseases, which usually injures the kidney. More and more studies have shown the pathogenic role and indicated that abnormal activation of the complement system was highly involved in the outbreak of autoimmune diseases. This review mainly introduced recent studies of complement system activation contributing to the pathogenesis of autoimmune diseases, including systemic lupus erythematosus, antiphospholipid syndrome, antineutrophil cytoplasmic antibody‐associated vasculitides, and so on. Understanding the pathogenic roles of complement activation in various autoimmune diseases will identify potential novel therapeutic targets on complement systems.

The complement system is important in the pathogenesis of a group of autoimmune diseases.

Targeting the complement system might provide us with novel target therapies in autoimmune diseases.

Eculizumab for Refractory Thrombosis in Antiphospholipid Syndrome

Recurrent thrombosis can present in antiphospholipid syndrome despite anticoagulation, antiplatelet, and immunosuppressive therapies.

Complement inhibition may be a therapeutic option for recurrent thrombosis associated with antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis with antiphospholipid antibodies. Dysregulation of the complement pathway has been implicated in APS pathophysiology. We report the successful use of eculizumab, an anti-C5 monoclonal antibody, in controlling and preventing recurrent thrombosis in a refractory case of APS. An 18-year-old female was diagnosed with APS after developing extensive, unprovoked deep vein thrombosis (DVT) of axillary, inferior vena cava, and brachiocephalic veins. Thrombophilia evaluation revealed triple-positive lupus anticoagulant, β-2 glycoprotein IgM, IgA, and anticardiolipin antibodies (each >40 U/mL) with persistently positive titers after 12 weeks. She was refractory to multiple anticoagulants alone (enoxaparin, fondaparinux, apixaban, rivaroxaban, and warfarin) with antiplatelet (aspirin and clopidogrel) and adjunctive therapies (hydroxychloroquine, immunosuppression with steroids and rituximab, and plasmapheresis). Despite these, she continued to develop recurrent thrombosis and additionally developed hepatic infarction and pulmonary embolism with failure to decrease titers after 6 weeks of plasma exchange. Following this event, eculizumab (600 mg weekly × 4 weeks followed by 900 mg every 2 weeks) was initiated in combination with fondaparinux, aspirin, clopidogrel, and hydroxychloroquine. She has remained on this regimen without recurrence of thrombosis. Our case suggests that eculizumab may have a role as a therapeutic option in refractory thrombosis in APS.

What Have We Learnt About the Treatment of Juvenile-Onset Systemic Lupus Erythematous Since Development of the SHARE Recommendations 2012?

Introduction

Juvenile-onset systemic lupus erythematous (JSLE) is a rare multisystem autoimmune disorder. In 2012, the Single Hub and Access point for pediatric Rheumatology in Europe (SHARE) initiative developed recommendations for the diagnosis/management of JSLE, lupus nephritis (LN) and childhood-onset anti-phospholipid syndrome (APS). These recommendations were based upon available evidence informing international expert consensus meetings.

Objective

To review new evidence published since 2012 relating to the management of JSLE, LN and APS in children, since the original literature searches informing the SHARE recommendations were performed.

Method

MEDLINE, EMBASE and CINAHL were systematically searched for relevant literature (2012-2021) using the following criteria: (1) English language studies; (2) original research studies regarding management of JSLE, LN, APS in children; (3) adult studies with 3 or more patients <18-years old, or where the lower limit of age range ≤16-years and the mean/median age is ≤30-years; (4) randomized controlled trials (RCTs), cohort studies, case control studies, observational studies, case-series with >3 patients. Three reviewers independently screened all titles/abstracts against predefined inclusion/exclusion criteria. All relevant manuscripts were reviewed independently by at least two reviewers. Data extraction, assessment of the level of evidence/methodological quality of the manuscripts was undertaken in-line with the original SHARE processes. Specific PUBMED literature searches were also performed to identify new evidence relating to each existing SHARE treatment recommendation.

Results

Six publications met the inclusion/exclusion criteria for JSLE: three RCTs, one feasibility trial, one case series. For LN, 16 publications met the inclusion/exclusion criteria: eight randomized trials, three open label prospective clinical trials, five observational/cohort studies. For APS, no publications met the inclusion criteria. The study with the highest evidence was an RCT comparing belimumab vs. placebo, including 93 JSLE patients. Whilst the primary-endpoint was not met, a significantly higher proportion of belimumab-treated patients met the PRINTO/ACR cSLE response to therapy criteria. New evidence specifically addressing each SHARE recommendation remains limited.

Conclusion

Since the original SHARE literature searches, undertaken >10-years ago, the main advance in JSLE treatment evidence relates to belimumab. Additional studies are urgently needed to test new/existing agents, and assess their long-term safety profile in JSLE, to facilitate evidence-based practice.

The Pathophysiology of The Antiphospholipid Syndrome: A Perspective From The Blood Coagulation System

The antiphospholipid syndrome (APS), a systemic autoimmune disease characterized by a hypercoagulability associated to vascular thrombosis and/or obstetric morbidity, is caused by the presence of antiphospholipid antibodies such as lupus anticoagulant, anti-β-2-glycoprotein 1, and/or anticardiolipin antibodies. In the obstetrical APS, antiphospholipid antibodies induce the production of proinflammatory cytokines and tissue factor by placental tissues and recruited neutrophils. Moreover, antiphospholipid antibodies activate the complement system which, in turn, induces a positive feedback leading to recruitment of neutrophils as well as activation of the placenta. Activation of these cells triggers myometrial contractions and cervical ripening provoking the induction of labor. In thrombotic and obstetrical APS, antiphospholipid antibodies activate endothelial cells, platelets, and neutrophils and they may alter the multimeric pattern and concentration of von Willebrand factor, increase the concentration of thrombospondin 1, reduce the inactivation of factor XI by antithrombin, increase the activation of factor XII, and reduce the activity of tissue plasminogen activator with the subsequent production of plasmin. All these effects result in less permeable clots, denser, thinner, and with more branched fibrin fibers which are more difficult to lysate. As a consequence, thrombosis, the defining clinical criterion of APS, complicates the clinical course of the patient.

The mosaic of autoimmunity - A taste for more. The 12th international congress of autoimmunity 2021 (AUTO12) virtual

Notwithstanding the fact that the 12th international congress of autoimmunity (AUTO12) was held virtual this year, the number of the abstracts submitted and those presented crossed the thousand marks. Leading investigators and researchers from all over the world presented the latest developments of their research in the domain of autoimmunity and its correlation with various diseases. In terms of mechanisms of autoimmunity, an update on the mechanisms behind the association of autoimmunity with systemic diseases focusing on hyperstimulation was presented during AUTO12. In addition, a new mechanism of ASIA syndrome caused by an intrauterine contraceptive device was revealed demonstrating a complete resolution of symptoms following device removal. In regard to the correlation between autoimmunity and neurogenerative diseases, the loss of structural protein integrity as the trigger of immunological response was shown. Schizophrenia as well, and its correlation to pro-inflammatory cytokines was also addressed. Furthermore, and as it was said AUTO12 virtual due to COVID-19 pandemic, various works were dedicated to SARS-CoV-2 infection and COVID-19 in terms of autoimmune mechanisms involved in the pathogenesis, treatment and complications of COVID-19. For instance, the correlation between autoimmunity and the severity of COVID-19 was viewed. Moreover, the presence and association of autoantibodies in COVID-19 was also demonstrated, as well as the clinical outcomes of COVID-19 in patients with rheumatic diseases. Finally, immune-mediated reactions and processes secondary to SARS-CoV-2 vaccination was displayed. Due to the immense importance of all of the topics addressed and while several hundreds of works were presented which cannot be summed up in one paper, we aimed hereby to highlight some of the outstanding abstracts and presentations during AUTO12.

Successful Treatment of Catastrophic Antiphospholipid Syndrome Using Rituximab: Case Report and Review of the Literature

BACKGROUND

Kidney involvement is a frequent complication of systemic lupus erythematosus (SLE) and kidney biopsy is essential in differentiating lupus nephritis (LN) from thrombotic microangiopathy (TMA) secondary to antiphospholipid autoantibodies (aPL). Association between antiphospholipid syndrome (APS) and acquired hemophilia due to inhibitors was very rarely described in SLE patients.

CASE PRESENTATION

We present the case of a 61-year-old male diagnosed with SLE who acquired deficiency of clotting factor VIII due to circulating inhibitors, admitted for acute kidney injury (AKI), microangiopathic hemolytic anemia, thrombocytopenia, and diplopia. Kidney biopsy showed TMA due to APS, but no signs of LN. Head computed tomography identified low dense areas in the white matter, suggesting small blood vessels' involvement. A diagnosis of probable catastrophic antiphospholipid syndrome (CAPS) was established and treatment with low molecular weight heparin, intravenous methylprednisolone, plasmapheresis, and rituximab was initiated, followed by resolution of AKI, diplopia, and TMA with complete depletion of CD19+B-lymphocytes (CD19+B-Ly) after one month. We further review the current knowledge regarding pathogenesis and management of CAPS in SLE patients.

CONCLUSIONS

Targeted therapy was possible after kidney biopsy, improving renal and general prognosis. CD19+B-Ly repopulation preceded biological relapse, so monitoring of CD19+B-Ly may serve as a tool to predict relapses and guide rituximab therapy.

Complement mediates binding and procoagulant effects of ultra-large HIT immune complexes

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by ultra-large immune complexes (ULICs) containing IgG antibodies to a multivalent antigen composed of platelet factor 4 (PF4) and heparin. The limitations of current anti-thrombotic therapy in HIT supports the need to identify additional pathways that may be targets for therapy. Activation of FcgRIIA by HIT ULICs initiates diverse procoagulant cellular effector functions. HIT ULICs are also known to activate complement, but the contribution of this pathway to the pathogenesis of HIT has not been studied in detail. We observed that HIT ULICs physically interact with C1q in buffer and plasma, activate complement via the classical pathway, promote co-deposition of IgG and activated C3 complement fragments (C3c) on neutrophil and monocyte cell surfaces. Complement activation by ULICs, in turn, facilitates Fcg receptor(R)-independent monocyte tissue factor expression, enhances IgG binding to the cell surface FcgRs and promotes platelet adhesion to injured endothelium. Inhibition of the proximal, but not terminal, steps in the complement pathway, abrogates monocyte tissue factor expression by HIT ULICs. Together, these studies suggest a major role for complement activation in regulating Fc-dependent effector functions of HIT ULICs, identify potential non-anticoagulant targets for therapy, and provide insights into the broader roles of complement in immune complex-mediated thrombotic disorders.

The Benefits of Complement Measurements for the Clinical Practice

The complement cascade is an evolutionary ancient innate immune defense system, playing a major role in the defense against infections. Its function in maintaining host homeostasis on activated cells has been emphasized by the crucial role of its overactivation in ever growing number of diseases, such as atypical hemolytic uremic syndrome (aHUS), autoimmune diseases as systemic lupus erythematosus (SLE), C3 glomerulopathies (C3GN), age-related macular degeneration (AMD), graft rejection, Alzheimer disease, and cancer, to name just a few. The last decade of research on complement has extended its implication in many pathological processes, offering new insights to potential therapeutic targets and asserting the necessity of reliable, sensitive, specific, accurate, and reproducible biomarkers to decipher complement role in pathology. We need to evaluate accurately which pathway or role should be targeted pharmacologically, and optimize treatment efficacy versus toxicity. This chapter is an introduction to the role of complement in human diseases and the use of complement-related biomarkers in the clinical practice. It is a part of a book intending to give reliable and standardized methods to evaluate complement according to nowadays needs and knowledge.

Markers of complement activation in plasma during quiescent phases in patients with catastrophic antiphospholipid syndrome

Accumulating evidence suggests that complement activation is a critical contributor to catastrophic antiphospholipid syndrome (CAPS). While complement activation and C5b-9 levels have been documented in acute CAPS, Ruffati et al report that patients with a history of CAPS have higher levels of C5a and C5b-9 even in the quiescent phase, suggesting an underlying defect in complement regulation.

Komplementinhibitoren: neue Therapeutika – neue Indikationen

Das Komplementsystem, ein klassisch transfusionsmedizinisches Thema, hat in den letzten Jahren in allen Bereichen der Medizin an Bedeutung gewonnen. Komplementinhibitoren werden aufgrund eines besseren Verständnisses der Pathophysiologie unterschiedlicher Erkrankungen in einem sich stetig erweiternden Krankheitsspektrum eingesetzt. Dieses reicht von typisch komplementassoziierten Erkrankungen wie der PNH (paroxysmale nächtliche Hämoglobinurie) bis hin zu akuten Krankheitsbildern mit einer Fehlregulation des Komplementsystems, wie COVID-19.

Current concepts in the diagnosis and management of antiphospholipid syndrome and ocular manifestations

Antiphospholipid syndrome (APS) is an autoimmune disorder associated with obstetrical complications, thrombotic complications involving both arteries and veins, and non-thrombotic manifestations affecting multiple other systems presenting in various clinical forms. Diagnosis requires the presence of antiphospholipid antibodies. The exact pathogenesis of APS is not fully known. However, it has recently been shown that activation of different types of cells by antiphospholipid antibodies plays an important role in thrombosis formation. Ocular involvement is one of the important clinical manifestations of APS and can vary in presentations. Therefore, as an ophthalmologist, it is crucial to be familiar with the ocular findings of APS to prevent further complications that can develop. Furthermore, the ongoing identification of new and specific factors contributing to the pathogenesis of APS may provide new therapeutic options in the management of the disease in the future.

B cells in primary antiphospholipid syndrome: Review and remaining challenges

It is now widely accepted that antiphospholipid antibodies (aPL) have direct pathogenic effects and that B cells, notably through aPL production, play a key role in the development of antiphospholipid syndrome (APS). Recent findings strengthened the implication of B cells with the description of specific B cell phenotype abnormalities and inborn errors of immunity involving B cell signaling in APS patients. In addition, it has been shown in preclinical models that cross-reactivity between APS autoantigens and mimotopes expressed by human gut commensals can lead to B cell tolerance breakdown and are sufficient for APS development. However, B cell targeting therapies are surprisingly not as effective as expected in APS compared to other autoimmune diseases. Elucidation of the B cell tolerance breakdown mechanisms in APS patients may help to develop and guide the use of novel therapeutic agents that target B cells or specific immune pathway.

Antiphospholipid syndrome: Complement activation, complement gene mutations, and therapeutic implications

Antiphospholipid syndrome (APS) is an acquired thromboinflammatory disorder characterized by the presence of antiphospholipid antibodies as well as an increased frequency of venous or arterial thrombosis and/or obstetrical morbidity. The spectrum of disease varies from asymptomatic to a severe form characterized by widespread thrombosis and multiorgan failure, termed catastrophic APS (CAPS). CAPS affects only about ∼1% of APS patients, often presents as a thrombotic microangiopathy and has a fulminant course with >40% mortality, despite the best available therapy. Animal models have implicated complement in the pathophysiology of thrombosis in APS, with more recent data from human studies confirming the interaction between the coagulation and complement pathways. Activation of the complement cascade via antiphospholipid antibodies can cause cellular injury and promote coagulation via multiple mechanisms. Finally, analogous to classic complement-mediated diseases such as atypical hemolytic uremic syndrome, a subset of patients with APS may be at increased risk for development of CAPS because of the presence of germline variants in genes crucial for complement regulation. Together, these data make complement inhibition an attractive and potentially lifesaving therapy to mitigate morbidity and mortality in severe thrombotic APS and CAPS.

Anti-phospholipid syndrome and COVID-19 thrombosis: connecting the dots

As the coronavirus disease 2019 (COVID-19) pandemic, which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is spreading rapidly worldwide, it has emerged as a leading cause of mortality, resulting in >1 million deaths over the past 10 months. The pathophysiology of COVID-19 remains unclear, posing a great challenge to the medical management of patients. Recent studies have reported an unusually high prevalence of thromboembolic events in COVID-19 patients, although the mechanism remains elusive. Several studies have reported the presence of aPLs in COVID-19 patients. We have noticed similarities between COVID-19 and APS, which is an autoimmune prothrombotic disease that is often associated with an infective aetiology. Molecular mimicry and endothelial dysfunction could plausibly explain the mechanism of thrombogenesis in acquired APS. In this review, we discuss the clinicopathological similarities between COVID-19 and APS, and the potential role of therapeutic targets based on the anti-phospholipid model for COVID-19 disease.

Immunosuppressive Treatment in Antiphospholipid Syndrome: Is It Worth It?

The antiphospholipid syndrome (APS) is characterized by the development of venous and/or arterial thrombosis and pregnancy morbidity in patients with persistent antiphospholipid antibodies (aPL). Catastrophic antiphospholipid syndrome (CAPS) is a life-threatening form of APS occurring in about 1% of cases. Lifelong anticoagulation with vitamin K antagonists remains the cornerstone of the therapy for thrombotic APS, but frequently the use of anticoagulation may be problematic due to the increased risk of bleeding, drug interactions, or comorbidities. Immunosuppressant drugs are widely used to treat several autoimmune conditions, in which their safety and effectiveness have been largely demonstrated. Similar evidence in the treatment of primary APS is limited to case reports or case series, and studies on a large scale lack. Immunomodulatory drugs may be an emerging tool in managing such particular situations, like refractory obstetrical complications, CAPS, or so-called APS non-criteria manifestations. In addition, immunomodulatory drugs may be useful in patients experiencing recurrent thromboembolic events despite optimized anticoagulant therapy. We did a comprehensive review of literature analyzing the possible role of immunomodulation in primary APS to provide a broad overview of potentially safe and effective target treatments for managing this devastating disease.

Treatment of thrombotic antiphospholipid syndrome in adults and children

PURPOSE OF REVIEW

Antiphospholipid syndrome (APS), more common than once believed, is an autoimmune disease best known for its high risk of incident and recurrent thrombotic events. The approach to treatment potentially differs from treatment of thrombosis in the general population, and this article endeavors to review the latest updates on this topic.

RECENT FINDINGS

The epidemiology of APS is being increasingly elucidated by large population-based studies, with APS perhaps affecting as many as 1 in 2000 individuals. Vitamin K antagonists, aspirin, and heparinoids continue to have obvious roles in the management of patients with APS. There has recently been intensive study of direct oral anticoagulants in APS, with the most recent randomized studies raising concerns about their inferiority to vitamin K antagonists, at least in some subgroups. Other approaches to treating APS beyond anticoagulants and antiaggregants are also receiving increased attention in mechanistic and preclinical studies with an eye toward future roles in patients with refractory and/or microvascular disease. Pediatric APS is identified as an area in desperate need of additional prospective research.

SUMMARY

Progress continues to be made in pursuit of improving the lives of individuals afflicted with APS. The most important future directions would seem to involve leveraging modern molecular technologies in order to improve subphenotyping of antiphospholipid antibody-positive individuals. This will help personalize risk profiles and ideally define the optimal approach to therapy based on future risk, rather than past morbid events.

[Endothelial dysfunction in thrombotic thrombocytopenic purpura: therapeutic perspectives]

Immune Thrombotic Thrombocytopenic Purpura (iTTP) is a rare but severe disease with a mortality rate of almost 100 % in the absence of adequate treatment. iTTP is caused by a severe deficiency in ADAMTS13 activity due to the production of inhibitory antibodies. Age has been shown to be a major prognostic factor. iTTP patients in the elderly (60yo and over) have more frequent organ involvement, especially heart and kidney failures compared with younger patients. They also have non-specific neurologic symptoms leading to a delayed diagnosis. Factors influencing this impaired survival among older patients remain unknown so far. Alteration of the functional capacity of involved organs could be part of the explanation as could be the consequences of vascular aging. In fact, severe ADAMTS13 deficiency is necessary but likely not sufficient for iTTP physiopathology. A second hit leading to endothelial activation is thought to play a central role in iTTP. Interestingly, the mechanisms involved in endothelial activation may share common features with those involved in vascular aging, potentially leading to endothelial dysfunction. It could thus be interesting to better investigate the causes of mid- and long-term mortality among older iTTP patients to confirm whether inflammation and endothelial activation really impact vascular aging and long-term mortality in those patients, in addition to their presumed role at iTTP acute phase. If so, further insights into the mechanisms involved could lead to new therapeutic targets.

Complement as a Therapeutic Target in Systemic Autoimmune Diseases

The complement system (CS) includes more than 50 proteins and its main function is to recognize and protect against foreign or damaged molecular components. Other homeostatic functions of CS are the elimination of apoptotic debris, neurological development, and the control of adaptive immune responses. Pathological activation plays prominent roles in the pathogenesis of most autoimmune diseases such as systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, dermatomyositis, and ANCA-associated vasculitis. In this review, we will review the main rheumatologic autoimmune processes in which complement plays a pathogenic role and its potential relevance as a therapeutic target.

The Complex Relationship between C4b-Binding Protein, Warfarin, and Antiphospholipid Antibodies

BACKGROUND

 Low levels of total C4b-binding protein (C4BPt), a circulating inhibitor of the classical/lectin complement pathways, were observed in patients with antiphospholipid antibodies (aPLs) and during warfarin treatment.

OBJECTIVES

 To investigate the associations between aPL and C4BPt in patients with persistently positive (++) aPL, with/without clinical manifestations and systemic lupus erythematosus (SLE), and in controls. Furthermore, we explored the impact of anticoagulation on C4BPt and in relation to complement activation.

METHODS

 In a cross-sectional design we investigated defined subgroups: primary (p) antiphospholipid syndrome (APS, N = 67), aPL++ individuals without clinical manifestations (aPL carriers, N = 15), SLE-aPL++ (N = 118, among them, secondary [s] APS, N = 56), aPL negative (-) SLE (SLE-aPL-, N = 291), and 322 controls. Clinical characteristics, including treatment, were tabulated. C4BPt was determined with a magnetic bead method. Complement proteins (C1q, C2, C3, C4, C3a, C3dg, sC5b-9, factor I [FI]) were measured. A mediation analysis was performed to decompose the total effect of aPL++ on C4BPt into the direct and indirect effects of aPL++ through warfarin.

RESULTS

 Overall, C4BPt is 20% decreased in aPL++ patients, regardless of SLE, APS, clinical manifestations, and aPL profile. C4BPt levels associate positively with complement proteins C1q, C2, C3, and C4, and negatively with complement activation product C3dg. In the SLE group, warfarin treatment contributes to approximately half of the C4BPt reduction (9%) CONCLUSION:  Both aPLs and warfarin are associated with C4BPt reduction. Complement activation in aPL++ patients may partly be explained by impaired inhibition through depressed C4BPt levels. Further studies are needed to understand the clinical implications.

16th International Congress on Antiphospholipid Antibodies Task Force Report on Antiphospholipid Syndrome Treatment Trends

Antiphospholipid syndrome (APS), an acquired autoimmune thrombophilia, is characterised by thrombosis and/or pregnancy morbidity in association with persistent antiphospholipid antibodies. The 16th International Congress on Antiphospholipid Antibodies Task Force on APS Treatment Trends reviewed the current status with regard to existing and novel treatment trends for APS, which is the focus of this Task Force report. The report addresses current treatments and developments since the last report, on the use of direct oral anticoagulants in patients with APS, antiplatelet agents, adjunctive therapies (hydroxychloroquine, statins and vitamin D), targeted treatment including rituximab, belimumab, and anti-TNF agents, complement inhibition and drugs based on peptides of beta-2-glycoprotein I. In addition, the report summarises potential new players, including coenzyme Q10, adenosine receptor agonists and adenosine potentiation. In each case, the report provides recommendations for clinicians, based on the current state of the art, and suggests a clinical research agenda. The initiation and development of appropriate clinical studies requires a focus on devising suitable outcome measures, including a disease activity index, an optimal damage index, and a specific quality of life index.

The clinical and serological associations of hypocomplementemia in a longitudinal sle cohort

BACKGROUND

In SLE, low complement is an important serological manifestation. Recent classification criteria include hypocomplementemia and one gives additional weight if both C3 and C4 are low. We evaluated patients with a history of, and those with persistently, low complement. As complement activation occurs in the antiphospholipid antibody syndrome, an analysis was also performed on those with positive antiphospholipid antibodies to evaluate thrombotic outcomes.

METHODS

In a longitudinal SLE cohort, organ manifestations, damage, C3, C4 and antiphospholipid antibodies were assessed quarterly. Using univariate and multivariate methods we compared those with and without a history of low C3, low C4 and both. We evaluated those who had a history of low complement at any time point, and those who had persistent hypocomplementemia. Further analysis considered thrombotic outcomes in patients with positive antiphospholipid antibodies and a history of low complement.

RESULTS

2399 patients were evaluated. Fifty-five percent had a history of low C3 and 47% low C4; 83 (4%) had persistently low C3 and 65 (3.2%) had persistently low C4. Hematological, renal and serological abnormalities associated with a history of low C3 but not low C4. With anticardiolipin antibodies, a history of hypocomplementemia (both C3 and C4 low) associated with stroke and deep venous thrombosis.

CONCLUSION

Low C4 was a weak marker in terms of the associated clinical and serological manifestations. Low C3 associated with renal involvement and poor renal outcomes. A history of both low C3 and C4 associated with stroke in the presence of lupus anticoagulant or anticardiolipin antibodies, and low C4 with digital gangrene (with lupus anticoagulant).

[Thrombotic microangiopathy in rheumatology: a link between thrombosis and autoimmunity]

Uncontrolled hypercoagulation and inflammation (thromboinflammation), which are both independent and closely related and amplifying each other pathological processes, form the basis for pathogenesis of a wide range of diseases and complications, including immuno-inflammatory (autoimmune) rheumatic diseases, with the development of potentially fatal injuries of internal organs. Thrombotic microangiopathy is one of the most prominent prototypes of thromboinflammatory pathological conditions. The close link between environmental factors, hemostasis genetic defects and the complement system, inflammation and autoimmunity as pathogenetic mechanisms of microthrombosis draws particular attention to studying thrombotic microangiopathy in immuno-inflammatory rheumatic diseases, primarily systemic lupus erythematosus, antiphospholipid syndrome and scleroderma renal crisis. In future, these studies may be important for expanding the idea of the role of autoimmune mechanisms in pathogenesis of critical hemostasis disorders in human diseases, and for developing new approaches to therapy. Recently, special attention has been paid to the treatment of systemic lupus erythematosus and antiphospholipid syndrome with eculizumab, which is humanized monoclonal IgG2/4k antibody that blocks the complement component C5a and the membrane attack complex (C5b-9) formation, and which is registered for the treatment of atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, as well as severe forms of myasthenia gravis and neuromyelitis optica. Further studies in this direction will create prerequisites for improving the prognosis not only in patients with orphan disorders, but also for widespread human diseases.

Complementopathies and precision medicine

The renaissance of complement diagnostics and therapeutics has introduced precision medicine into a widened field of complement-mediated diseases. In particular, complement-mediated diseases (or complementopathies) with ongoing or published clinical trials of complement inhibitors include paroxysmal nocturnal hemoglobinuria, cold agglutinin disease, hemolytic uremic syndrome, nephropathies, HELLP syndrome, transplant-associated thrombotic microangiopathy, antiphospholipid antibody syndrome, myasthenia gravis, and neuromyelitis optica. Recognizing that this field is rapidly expanding, we aim to provide a state-of-the-art review of (a) current understanding of complement biology for the clinician, (b) novel insights into complement with potential applicability to clinical practice, (c) complement in disease across various disciplines (hematology, nephrology, obstetrics, transplantation, rheumatology, and neurology), and (d) the potential future of precision medicine. Better understanding of complement diagnostics and therapeutics will not only facilitate physicians treating patients in clinical practice but also provide the basis for future research toward precision medicine in this field.

An update on the management of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by recurrent venous or arterial thrombosis with or without pregnancy morbidity in the presence of persistent antiphospholipid (aPL) autoantibodies. Anticoagulation has, until now, formed the cornerstone of treatment but a significant proportion of patients continue to experience thrombosis and pregnancy morbidity despite this treatment. Thrombosis is the most common cause of mortality and accounts for two fifths of deaths. Direct oral anticoagulant drugs represent an attractive alternative to conventional vitamin K antagonist drugs but emerging evidence suggests these may not be suitable for high-risk patients with thrombotic APS. Laboratory studies and case reports of the successful use of different classes of drugs in APS is increasing our understanding of the other pathophysiological mechanisms which may contribute to the high morbidity of APS. This review summarizes current accepted anticoagulant treatment for APS and examines other potential drugs such as immunomodulating agents, statins and novel agents such as sirolimus and defibrotide.

Thrombotic microangiopathy in the course of catastrophic antiphospholipid syndrome successfully treated with eculizumab: case report and systematic review of the literature

Objective

The purpose of this study was to characterize the role of eculizumab, a monoclonal antibody against the terminal complement component C5, in patients with catastrophic antiphospholipid syndrome (CAPS).

Methods

We present a case report of a patient with systemic lupus erythematosus (SLE) and CAPS treated with eculizumab, as well as results of a systematic review of the literature.

Results

Including our patient, we identified 11 case reports of patients with CAPS treated with eculizumab. All of them had partial or total remission of symptoms.

Conclusion

Data on eculizumab efficacy in CAPS are promising but are limited to single case reports. More studies are needed to develop evidence-based recommendations for eculizumab use in CAPS.

The antiphospholipid syndrome - often overlooked cause of vascular occlusions?

The antiphospholipid syndrome (APS) was fully recognized as a clinical entity in the early 1980s. Still, more than 30 years later, the epidemiology of APS is not well described, and furthermore, APS remains a challenge in terms of both diagnostic issues and clinical praxis involving a wide range of specialties. To date, there are no diagnostic criteria for APS. The present classification criteria rely on a combination of clinical manifestations and persistently positive tests for antiphospholipid antibodies (aPL). Clinical symptoms comprise vascular thrombosis, which can affect any vascular bed, including venous, microvascular and arterial vessels, and a set of pregnancy morbidities including early and late miscarriages, foetal death and preeclampsia. APS is more frequent among patients with other autoimmune diseases, and it is especially common in systemic lupus erythematosus (SLE). Importantly, APS symptoms can present in almost any medical specialty, but general knowledge and most previous clinical studies have essentially been confined to haematology, rheumatology and obstetrics/gynaecology. However, recent data demonstrate a relatively high prevalence of aPL also in patients from the general population who suffer from vascular occlusions or pregnancy complications. It is important that these patients are recognized by the general health care since APS is a treatable condition. This review aims to summarize the present knowledge on the history, pathogenesis, clinical manifestations and treatment of APS in order to urge a wide range of clinicians to consider comprehensive assessment of all patients where the diagnosis APS may be conceivable.

Pediatric APS: State of the Art

PURPOSE OF REVIEW

The purpose of this report is to review recent research findings on APS in children and neonates.

RECENT FINDINGS

European evidence-based recommendations for diagnosis and treatment of pediatric APS has recently been published by the SHARE Initiative. Recent studies have shown a high prevalence of non-thrombotic manifestations in children with aPL, domains 4/5 specificity of 'innocent' anti-β2GPI antibodies in infants, and a higher risk for developmental delays and learning disabilities, hence, the need for neurodevelopmental monitoring in children born to mothers with APS. An International effort on creating a new diagnostic criteria for APS is underway. Pediatric APS is a rare disease with significant differences from the APS in adults. Majority of the children with persistently positive aPL do not develop thrombotic events; however, relatively higher proportion of thrombosis in children is related to aPL positivity compared to adults; this may partly be due to the absence of common pro-thrombotic "second-hit" risk factors of adults such as atherosclerosis and cigarette smoking. Diagnosis of APS in children may be delayed or missed when adult APS criteria are used, because in pediatric APS, non-thrombotic clinical manifestations such as thrombocytopenia, hemolytic anemia, and neurological disorders such as migraine, epilepsy, and chorea may precede thrombotic manifestations. Around 20% of the children initially diagnosed with primary APS eventually develop SLE. Neonatal APS is rare; however, the offspring of mothers with APS are at a higher risk for developmental delays and learning disabilities; prematurity and IUGR may increase this risk. Regular assessment of neurodevelopmental status of these children should be performed. Thrombosis is a rare event in the offspring of mothers with APS; anticoagulation of such infants is not recommended. An international effort to create a new diagnostic criteria for APS is underway.

Neuropsychiatric lupus: new mechanistic insights and future treatment directions

Patients with systemic lupus erythematosus (SLE) frequently show symptoms of central nervous system (CNS) involvement, termed neuropsychiatric SLE (NPSLE). The CNS manifestations of SLE are diverse and have a broad spectrum of severity and prognostic implications. Patients with NPSLE typically present with nonspecific symptoms, such as headache and cognitive impairment, but might also experience devastating features, such as memory loss, seizures and stroke. Some features of NPSLE, in particular those related to coagulopathy, have been characterized and an evidence-based treatment algorithm is available. The cognitive and affective manifestations of NPSLE, however, remain poorly understood. Various immune effectors have been evaluated as contributors to its pathogenesis, including brain-reactive autoantibodies, cytokines and cell-mediated inflammation. Additional brain-intrinsic elements (such as resident microglia, the blood-brain barrier and other neurovascular interfaces) are important facilitators of NPSLE. As yet, however, no unifying model has been found to underlie the pathogenesis of NPSLE, suggesting that this disease has multiple contributors and perhaps several distinct aetiologies. This heterogeneity presents a challenge for clinicians who have traditionally relied on empirical judgement in choosing treatment modalities for patients with NPSLE. Improved understanding of this manifestation of SLE might yield further options for managing this disease.

Complement activity and complement regulatory gene mutations are associated with thrombosis in APS and CAPS

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity in the presence of antiphospholipid antibodies, including anti-β2-glycoprotein-I (anti-β2GPI), that are considered central to APS pathogenesis. Based on animal studies showing a role of complement in APS-related clinical events, we used the modified Ham (mHam) assay (complement-dependent cell killing) and cell-surface deposition of C5b-9 to test the hypothesis that complement activation is associated with thrombotic events in APS. A positive mHam (and corresponding C5b-9 deposition) were present in 85.7% of catastrophic APS (CAPS), 35.6% of APS (and 68.5% of samples collected within 1 year of thrombosis), and only 6.8% of systemic lupus erythematosus (SLE) sera. A positive mHam assay was associated with triple positivity (for lupus anticoagulant, anticardiolipin, and anti-β2GPI antibodies) and recurrent thrombosis. Patient-derived anti-β2GPI antibodies also induced C5b-9 deposition, which was blocked completely by an anti-C5 monoclonal antibody, but not by a factor D inhibitor, indicating that complement activation by anti-β2GPI antibodies occurs primarily through the classical complement pathway. Finally, patients with CAPS have high rates of rare germline variants in complement regulatory genes (60%), compared with patients with APS (21.8%) or SLE (28.6%) or normal controls (23.3%), and have mutations at a rate similar to that of patients with atypical hemolytic uremic syndrome (51.5%). Taken together, our data suggest that anti-β2GPI antibodies activate complement and contribute to thrombosis in APS, whereas patients with CAPS have underlying mutations in complement regulatory genes that serve as a "second hit," leading to uncontrolled complement activation and a more severe thrombotic phenotype.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

Eculizumab in refractory catastrophic antiphospholipid syndrome: a case report and systematic review of the literature

Catastrophic antiphospholipid syndrome (CAPS) is a rare disorder, characterized by the development of multiple vascular thrombosis over a short period of time, in patients with persistently detectable antiphospholipid antibodies (aPLs). The vascular occlusions predominantly affect small vessels. The overall mortality is 36.9%, despite the recent progress in the therapeutic approach. It has been shown that aPLs are able to induce a hypercoagulability state through different mechanisms of action, including complement activation, which in turn plays a key role in the pathogenesis of some thrombotic microangiopathies. Consequently, complement inhibition may be proposed as a targeted intervention to effectively prevent the progression of the microthrombotic storm. The employment of the complement inhibitor eculizumab has been proposed in CAPS on the basis of occasional reports and expert opinion. We report the case of a 54-year-old woman with a CAPS refractory to conventional therapies, who was successfully treated with eculizumab. The administration of this anti-C5 monoclonal antibody aborted the acute progressive thrombotic events and prevented further clinical episodes of thrombosis in the following year. We also faced our case to a systematic literature review, by analyzing all reported cases of CAPS in which eculizumab was added to conventional therapy. Even if further investigation is needed, our results suggest that the inhibition of one mechanism of aPL-induced organ damage may be an add-on treatment for this condition.

Atypical hemolytic uremic syndrome: a syndrome in need of clarity

Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA) originally understood to be limited to renal and hematopoietic involvement. Whereas aberrations in complement regulatory proteins (CRPs), C3 or complement factor B (CFB) are detected in ∼60% of patients, a complement-derived pathogenesis that reflects dysregulation of the alternative pathway (AP) of complement activation is present in ∼90% of patients. aHUS remains a diagnosis of exclusion. The discovery of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) and its utility in the diagnosis of thrombotic thrombocytopenic purpura (TTP) has resulted in the appreciation that cases of aHUS have been inappropriately diagnosed as TTP. Thus there has been an evolving appreciation of clinical manifestations of aHUS that renders the appellation aHUS misleading. This article will review the pathogenesis and the evolving clinical presentations of aHUS, present a hypothesis that there can be a phenotypic expression of aHUS due to a complement storm in a disorder where direct endothelial damage occurs and discuss future areas of research to more clearly define the clinical spectrum and management of aHUS.

Complement Therapeutics in Autoimmune Disease

Many autoimmune diseases are characterized by generation of autoantibodies that bind to host proteins or deposit within tissues as a component of immune complexes. The autoantibodies can activate the complement system, which can mediate tissue damage and trigger systemic inflammation. Complement inhibitory drugs may, therefore, be beneficial across a large number of different autoimmune diseases. Many new anti-complement drugs that target specific activation mechanisms or downstream activation fragments are in development. Based on the shared pathophysiology of autoimmune diseases, some of these complement inhibitory drugs may provide benefit across multiple different diseases. In some antibody-mediated autoimmune diseases, however, unique features of the autoantibodies, the target antigens, or the affected tissues may make it advantageous to block individual components or pathways of the complement system. This paper reviews the evidence that complement is involved in various autoimmune diseases, as well as the studies that have examined whether or not complement inhibitors are effective for treating these diseases.

Complement in the Pathophysiology of the Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is characterized by thrombosis and pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). Complement is a system of enzymes and regulatory proteins of the innate immune system that plays a key role in the inflammatory response to pathogenic stimuli. The complement and coagulation pathways are closely linked, and expanding data indicate that complement may be activated in patients with aPL and function as a cofactor in the pathogenesis of aPL-associated clinical events. Complement activation by aPL generates C5a, which induces neutrophil tissue factor-dependent procoagulant activity. Beta-2-glycoprotein I, the primary antigen for pathogenic aPL, has complement regulatory effects in vitro. Moreover, aPL induce fetal loss in wild-type mice but not in mice deficient in specific complement components (C3, C5). Antiphospholipid antibodies also induce thrombosis in wild type mice and this effect is attenuated in C3 or C6 deficient mice, or in the presence of a C5 inhibitor. Increased levels of complement activation products have been demonstrated in sera of patients with aPL, though the association with clinical events remains unclear. Eculizumab, a terminal complement inhibitor, has successfully been used to treat catastrophic APS and prevent APS-related thrombotic microangiopathy in the setting of renal transplant. However, the mechanisms of complement activation in APS, its role in the pathogenesis of aPL related complications in humans, and the potential of complement inhibition as a therapeutic target in APS require further study.