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

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

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.

A Review of Complement Activation in SLE

Purpose of Review

Complement activation is a key event in the pathogenesis of tissue inflammation and injury in systemic lupus erythematosus (SLE). This review is aimed at comparing the usefulness of measurement of complement proteins in serum/plasma (C3, C4) to complement activation (split) products in plasma and on circulating blood cells for SLE diagnosis, disease monitoring, and prognosis.

Recent Findings

Complement split products, C3dg, iC3b, and C4d, are elevated in SLE, and C3dg/C3 and iC3b/C3 ratios correlate with active SLE. C4d also is higher in patients with lupus nephritis. An elevated level of the alternative pathway split product, Bb, in early lupus pregnancy is a predictor of adverse outcomes in SLE patients with antiphospholipid antibodies. Elevated levels of cell-bound complement activation products (CB-CAPs), namely, B cell-bound C4d (BC4d) and erythrocyte-bound C4d (EC4d), within a multiparameter assay panel, may predict transition to SLE more than other lupus biomarkers. EC4d better correlates with lupus disease activity than low plasma complement levels. Elevated platelet-bound C4d (PC4d) correlates with thrombosis in SLE. Both EC4d and PC4d are increased in primary and secondary anti-phospholipid syndrome, and anti-beta2glycoproteinI antibodies may directly activate the complement system.

Summary

Abnormal levels of plasma complement split products and CB-CAPs support complement activation as an important pathogenetic mechanism in SLE and the antiphospholipid syndromes. These tests show promise for the diagnosis of SLE and monitoring of disease activity.

Clinical characteristics, inflammation and coagulation status in patients with immunological disease-related chronic cerebrospinal venous insufficiency

Background

Immunological disease-related chronic cerebrospinal venous insufficiency (CCSVI) is rarely reported. This study aimed to analyze clinical characteristics, inflammation, and coagulation status in patients with immunological disease-related CCSVI.

Methods

Patients with CCSVI were enrolled from 2017 to 2019 and divided into three cohorts based on their immunological disease backgrounds, including groups with confirmed autoimmune disease, with suspected/subclinical autoimmune disease, and with non-immunological etiology. Immunological, inflammatory, and thrombophilia biomarker assay in blood samples were obtained. Mann-Whitney U test or Fisher’s exact test was used to compare continuous variables or categorical variables between the CCSVI patients with or without the immunological etiology. Spearman’s correlation analysis was conducted among age, baseline neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), interleukin-6 (IL-6), C-reactive protein (CRP), and neuron-specific enolase (NSE) in the three groups.

Results

A total of 255 consecutive patients with CCSVI were enrolled, including three subgroups: CCSVI with confirmed autoimmune disease (n=41), CCSVI with suspected/subclinical autoimmune disease (n=116) and CCSVI with non-immunological etiology (n=98). In the first subgroup, a series of 41 cases was confirmed with eight different autoimmune diseases including antiphospholipid syndrome (n=18), Sjögren’s syndrome (n=8), immunoglobulin G4-related disease (n=7), Behçet’s disease (n=2), autoimmune hepatitis (n=2), Wegener's granulomatosis (n=2), systemic sclerosis (n=1) and AQP4 antibody-positive neuromyelitis optica spectrum disorder (n=1). Groups with immunological etiology did not show a higher incidence of thrombophilia or increased pro-inflammatory biomarkers (e.g., neutrophil, IL-6). However, patients with non-immunological etiology had a higher baseline level of CRP. Additionally, baseline PLR was moderately correlated to NLR and CRP in CCSVI patients with non-immunological etiology and suspected/subclinical autoimmune disease.

Conclusions

The formation of CCSVI may be based on the inflammatory process, facilitated by multiple risk factors, among which medical history of immunological diseases may play a significant role due to the intricate relationship between inflammation and coagulation. Moreover, CCSVI may also cause an independent inflammatory injury in venous walls, leading to focal stenosis or thrombus, without attacks from autoimmune antibodies.

Complement in sickle cell disease and targeted therapy: I know one thing, that I know nothing

Sickle cell disease (SCD) is a common inherited clinical syndrome, characterized by the presence of hemoglobin S. Anemia, susceptibility to infections and episodes of vaso-occlusive crisis (VOC) are among its features. Since SCD complications (VOC or delayed hemolytic transfusion reaction/DHTR) lead to significant morbidity and mortality, a number of studies have addressed their pathophysiology Although SCD pathophysiology has been mainly attributed to the interaction between sickle cells and neutrophils, platelets or endothelial cells in small vessels leading to hemolysis, the role of complement activation has been increasingly investigated. Importantly, complement inhibition with eculizumab has shown beneficial effects in DHTR. Given the unmet clinical need of novel therapeutics in SCD, our review summarizes current understanding of (a) complement system for the clinician, (b) complement activation in SCD both in asymptomatic state and severe clinical manifestations, (c) probable underlying mechanisms of complement activation in SCD, and (d) new therapeutic perspective of complement inhibition.

[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.

Demystifying COVID-19 lung pathology: A clinicopathological study of postmortem core needle biopsy

Background:

Atypical presentation of coronavirus disease-19 (COVID-19) from classic acute respiratory distress syndrome needs to be extensively evaluated to understand the pathophysiology to optimize the management protocol for severely ill patients to abrogate the terminal event.

Methods:

Autopsy core needle biopsies of lungs were obtained from 12 patients who died with COVID-19. Routine histopathological examination of lung tissue along with immunohistochemical analysis of C4d complement staining was studied. Formalin-fixed paraffin-embedded biopsy material was also subjected to real-time reverse transcription-polymerase chain reaction for severe acute respiratory syndrome – coronavirus (SARS-CoV2) gene.

Results:

In the study, all the deceased patients were symptomatic with two-thirds suffering from isolated SARS-CoV2-related pneumonia while remaining one-third had secondary COVID-19 infection. Histopathological evaluation highlights diffuse alveolar damage as the predominant pattern; however, complement-mediated endothelial injury of septal microvasculature, and microthrombi was also distinctly observed with increased serum levels of D-Dimer and fibrinogen-degradation products. The patients who had extrapulmonary manifestations at the time of presentation also showed pulmonary vascular lesions on histopathologic examination. Our study confirms the presence of coagulopathy and immune-mediated microthrombi in pulmonary septal microvasculature in patients with severe disease.

Conclusion:

The results of our small series of patients highlight the possibility of immune-mediated pulmonary vascular injury and thrombosis which has the potential to evolve into large vessel thrombosis and pulmonary embolism in critically ill patients. Definitive therapeutic management protocol including thromboembolic prophylaxis and development of effective immune-modulatory target could possibly reduce mortality in severely ill patients.

Successful outcome with eculizumab treatment in a patient with antiphospholipid syndrome presenting with an unusual thrombotic storm

Catastrophic Antiphospholipid Syndrome (CAPS) is a life-threatening complication of APS requiring complex management to optimize patient outcome. We describe a 54-year-old man with APS with history of splanchnic vein thrombosis, a Factor II G20210A heterozygote, autoimmune hemolytic anemia and thrombocytopenia. He developed sudden onset of severe flank pain due to spontaneous bilateral adrenal hemorrhage while on warfarin with a therapeutic INR. Despite unfractionated heparin and initial clinical improvement, severe thrombocytopenia developed requiring dexamethasone, rituximab, and romiplostim. Hospitalization was complicated further by thrombosis of the inferior vena cava, pulmonary embolism, and painful violaceous patches on his neck and ear cartilages. Punch biopsy of lesions revealed C5b-C9 deposition of small vessel thromboses. Although the inciting event for his thrombotic storm remains uncertain, anti-complement therapy with eculizumab provided rapid and durable lesion resolution. Eculizumab was discontinued after 6 months and patient remains in remission without recurrent thrombosis. This case provides insight on the management of CAPS, including the use of eculizumab.

Distinct genetic profile with recurrent population-specific missense variants in Korean adult atypical hemolytic uremic syndrome

INTRODUCTION

Atypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy (TMA), characterized by micro-angiopathic hemolytic anemia, thrombocytopenia, and renal failure. In more than half of cases, genetic defects leading to overactivation of the alternative complement system have been identified. In this study, we investigated genetic defects in Korean adult patients with aHUS.

MATERIALS AND METHODS

Sixty-six Korean adult patients with aHUS were ascertained from the Korean TMA Registry. Genetic variants of 15 aHUS-related genes (eight core genes [CFH, CFB, CFI, CD46, C3, THBD, PLG, and DGKE] and seven candidate genes [CFP, C4BPA, and CHFR1-5]) were analyzed from exome sequencing data. Multiplex ligation-dependent probe amplification of CFH and related genes was performed to detect hybrid genes or large deletions.

RESULTS

Thirty patients (45%) had at least one aHUS-related variant (s) in eight core genes (total 40 variant alleles). The most frequently affected gene was CFH (13/40, 32%), followed by THBD (8/40, 20%) and CD46 (7/40, 18%). The two most common variants were Asp486Tyr of THBD (N = 7) and Tyr1058His-Val1060Leu of CFH (N = 5, linked on the same allele), accounting for 30% (12/40). In seven candidate genes, 19 variants were detected. When combined, 40 patients (61%) had at least one variant in 15 core or candidate genes. No patients had anti-CFH Ab or hybrid gene/CFHR1 homozygous deletions.

CONCLUSIONS

The genetic profile of Korean adult aHUS was unique with recurrent missense variants, demonstrating ethnicity- and age-dependent differences in the genetic background of aHUS.

Direct activation of the alternative complement pathway by SARS-CoV-2 spike proteins is blocked by factor D inhibition

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious respiratory virus that can lead to venous/arterial thrombosis, stroke, renal failure, myocardial infarction, thrombocytopenia, and other end-organ damage. Animal models demonstrating end-organ protection in C3-deficient mice and evidence of complement activation in humans have led to the hypothesis that SARS-CoV-2 triggers complement-mediated endothelial damage, but the mechanism is unclear. Here, we demonstrate that the SARS-CoV-2 spike protein (subunit 1 and 2), but not the N protein, directly activates the alternative pathway of complement (APC). Complement-dependent killing using the modified Ham test is blocked by either C5 or factor D inhibition. C3 fragments and C5b-9 are deposited on TF1PIGAnull target cells, and complement factor Bb is increased in the supernatant from spike protein–treated cells. C5 inhibition prevents the accumulation of C5b-9 on cells, but not C3c; however, factor D inhibition prevents both C3c and C5b-9 accumulation. Addition of factor H mitigates the complement attack. In conclusion, SARS-CoV-2 spike proteins convert nonactivator surfaces to activator surfaces by preventing the inactivation of the cell-surface APC convertase. APC activation may explain many of the clinical manifestations (microangiopathy, thrombocytopenia, renal injury, and thrombophilia) of COVID-19 that are also observed in other complement-driven diseases such as atypical hemolytic uremic syndrome and catastrophic antiphospholipid antibody syndrome. C5 inhibition prevents accumulation of C5b-9 in vitro but does not prevent upstream complement activation in response to SARS-CoV-2 spike proteins.

Antiphospholipid syndrome

Antiphospholipid syndrome is one of the more common acquired causes of hypercoagulability. Its major presentations are thrombotic (arterial, venous, or microvascular) and pregnancy morbidity (miscarriages, late intrauterine fetal demise, and severe pre-eclampsia). Classification criteria include 3 different antiphospholipid antibodies: lupus anticoagulant, anticardiolipin, and anti-beta 2 glycoprotein I. Management includes both preventive strategies (low-dose aspirin, hydroxychloroquine) and long-term anticoagulation after thrombosis.

Microvascular thrombosis: experimental and clinical implications

A significant amount of clinical and research interest in thrombosis is focused on large vessels (eg, stroke, myocardial infarction, deep venous thrombosis, etc.); however, thrombosis is often present in the microcirculation in a variety of significant human diseases, such as disseminated intravascular coagulation, thrombotic microangiopathy, sickle cell disease, and others. Further, microvascular thrombosis has recently been demonstrated in patients with COVID-19, and has been proposed to mediate the pathogenesis of organ injury in this disease. In many of these conditions, microvascular thrombosis is accompanied by inflammation, an association referred to as thromboinflammation. In this review, we discuss endogenous regulatory mechanisms that prevent thrombosis in the microcirculation, experimental approaches to induce microvascular thrombi, and clinical conditions associated with microvascular thrombosis. A greater understanding of the links between inflammation and thrombosis in the microcirculation is anticipated to provide optimal therapeutic targets for patients with diseases accompanied by microvascular thrombosis.

Ex vivo assays to detect complement activation in complementopathies

In complement-driven thrombotic microangiopathies, failure to regulate complement activation leads to end-organ damage. The modified Ham (mHam) test measures complement-mediated killing of a nucleated cell in vitro but lacks a confirmatory assay and reliable positive controls. We demonstrate that C5b-9 accumulation on the surface of TF1 PIGAnull cells correlates with cell killing in the mHam. We also show that Sialidase treatment of cells or addition of Shiga toxin 1 to human serum serve as a more reliable positive control for the mHam than cobra venom factor or lipopolysaccharide. Simultaneously performing the mHam and measuring C5b-9 accumulation either in GVB⁺⁺ or GVB⁰ MgEGTA buffer with the addition of complement pathway specific inhibitors (anti-C5 antibody or a factor D inhibitor, ACH-145951) can be used to localize defects in complement regulation. As more targeted complement inhibitors become available, these assays may aid in the selection of personalized treatments for patients with complement-mediated diseases.

Emerging evidence of a COVID-19 thrombotic syndrome has treatment implications

Reports of widespread thromboses and disseminated intravascular coagulation (DIC) in patients with coronavirus disease 19 (COVID-19) have been rapidly increasing in number. Key features of this disorder include a lack of bleeding risk, only mildly low platelet counts, elevated plasma fibrinogen levels, and detection of both severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and complement components in regions of thrombotic microangiopathy (TMA). This disorder is not typical DIC. Rather, it might be more similar to complement-mediated TMA syndromes, which are well known to rheumatologists who care for patients with severe systemic lupus erythematosus or catastrophic antiphospholipid syndrome. This perspective has critical implications for treatment. Anticoagulation and antiviral agents are standard treatments for DIC but are gravely insufficient for any of the TMA disorders that involve disorders of complement. Mediators of TMA syndromes overlap with those released in cytokine storm, suggesting close connections between ineffective immune responses to SARS-CoV-2, severe pneumonia and life-threatening microangiopathy.

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.

Repurposing Immunomodulatory Therapies against Coronavirus Disease 2019 (COVID-19) in the Era of Cardiac Vigilance: A Systematic Review

The ongoing coronavirus disease 2019 (COVID-19) pandemic has resulted in efforts to identify therapies to ameliorate adverse clinical outcomes. The recognition of the key role for increased inflammation in COVID-19 has led to a proliferation of clinical trials targeting inflammation. The purpose of this review is to characterize the current state of immunotherapy trials in COVID-19, and focuses on associated cardiotoxicities, given the importance of pharmacovigilance. The search terms related to COVID-19 were queried in ClinicalTrials.gov. A total of 1621 trials were identified and screened for interventional trials directed at inflammation. Trials (n = 226) were fully assessed for the use of a repurposed drug, identifying a total of 141 therapeutic trials using a repurposed drug to target inflammation in COVID-19 infection. Building on the results of the Randomized Evaluation of COVID-19 Therapy (RECOVERY) trial demonstrating the benefit of low dose dexamethasone in COVID-19, repurposed drugs targeting inflammation are promising. Repurposed drugs directed at inflammation in COVID-19 primarily have been drawn from cancer therapies and immunomodulatory therapies, specifically targeted anti-inflammatory, anti-complement, and anti-rejection agents. The proposed mechanisms for many cytokine-directed and anti-rejection drugs are focused on evidence of efficacy in cytokine release syndromes in humans or animal models. Anti-complement-based therapies have the potential to decrease both inflammation and microvascular thrombosis. Cancer therapies are hypothesized to decrease vascular permeability and inflammation. Few publications to date describe using these drugs in COVID-19. Early COVID-19 intervention trials have re-emphasized the subtle, but important cardiotoxic sequelae of potential therapies on outcomes. The volume of trials targeting the COVID-19 hyper-inflammatory phase continues to grow rapidly with the evaluation of repurposed drugs and late-stage investigational agents. Leveraging known clinical safety profiles and pharmacodynamics allows swift investigation in clinical trials for a novel indication. Physicians should remain vigilant for cardiotoxicity, often not fully appreciated in small trials or in short time frames.

Coronavirus disease 2019 (COVID-19) and immune-mediated inflammatory rheumatic diseases: at the crossroads of thromboinflammation and autoimmunity

Inflammation and coagulation are key basic mechanism of protection against all potentially pathogenic mechanical and biological factors targeting human organism from inner and outer environment. On the other hand, uncontrolled inflammation results in hypercoagulation, inhibition of anticoagulation and alteration of mechanisms responsible for resolution of inflammation, while production of “procoagulant” mediators (thrombin, tissue factor and others), activation of platelets and of vascular endothelial cells maintains inflammation. All factors taken together serve as the basis for a pathological process called thromboinflammation or immunothrombosis. Currently thromboinflammation is considered in the broad sense as a universal pathogenetic mechanism of numerous widespread acute and chronic conditions, including immune-mediated (autoimmune) inflammatory rheumatic diseases, oftentimes complicated by severe irreversible damage to vital organs. Thromboinflammation gained specific attention during СОVID-19 (coronavirus disease 2019) pandemic, caused by SARS-Cov-2 (severe acute respiratory syndrome Coronavirus-2). COVID-19 is considered currently as systemic thromboinflammation syndrome, manifesting via generalized thrombosis of arterial and venous macro- and microvasculature, termed as COVID-19-coagulopathy. The paper discusses common pathogenetic coagulopathy mechanisms in COVID-19 and immune-mediated (autoimmune) inflammatory rheumatic diseases (IMRDs), associated with overproduction of antiphospholipid antibodies, activation of the complement system, and dis-regulated synthesis of proinflammatory cytokines, etc. Delineating the autoimmune subtype of thromboinflammation, identification of genetic (i.e., genes encoding the complement system and others) and molecular-biologic biomarkers associated with higher occurrence of COVID-19-coagulopathy are the most relevant undertakings for the current practice. Gaining insights into mechanisms of thromboinflammation and converting them into potential pharmacotherapies of IMDs would facilitate and accelerate the drafting of effective therapeutic strategies for COVID-19. 

Coagulopathy and thromboembolic events in patients with SARS-CoV-2 infection: pathogenesis and management strategies

In October 2019, a viral infectious disease appeared in the city of Wuhan in China. A new betacoronavirus, SARS-CoV-2, has been recognized as the responsible pathogen in this infection. Although coronavirus disease is principally expressed as a pulmonary infection, critical SARS-CoV-2 infection is frequently complicated with coagulopathy, and thromboembolic events are recognizable in several patients. Dehydration, acute inflammatory condition, protracted immobilization during disease, existence of multiple cardiovascular risk factors such as diabetes, obesity or hypertension, previous coronary artery disease, ischemic stroke, peripheral artery disease are frequent comorbidities in SARS-CoV-2 hospitalized subjects, which possibly augment thrombo-embolic risk. However, other causal factors can still be identified such as unrestricted angiotensin II action, the use of immunoglobulins, an increased production of adhesion molecules able to induce vascular inflammation and endothelial activation, complement stimulation, excessive production of neutrophil extracellular traps (NETs), and increased platelet count. Low-molecular-weight heparin should be chosen as early treatment because of its anti-inflammatory action and its ability to antagonize histones and so defend the endothelium. However, several therapeutic possibilities have also been proposed such as fibrinolytic treatment, drugs that target NETs, and complement inhibition. Nevertheless, although the violence of the pandemic may suggest the use of heroic treatments to reduce the frightening mortality that accompanies SARS-CoV-2 infection, we believe that experimental treatments should only be used within approved and controlled protocols, the only ones that can provide useful and specify information on the validity of the treatments.

Coagulopathy in COVID-19: Focus on vascular thrombotic events

SARS-CoV-2 causes a phenotype of pneumonia with diverse manifestation, which is termed as coronavirus disease 2019 (COVID-19). An impressive high transmission rate allows COVID-19 conferring enormous challenge for clinicians worldwide, and developing to a pandemic level. Combined with a series of complications, a part of COVID-19 patients progress into severe cases, which critically contributes to the risk of fatality. To date, coagulopathy has been found as a prominent feature of COVID-19 and severe coagulation dysfunction may be associated with poor prognosis. Coagulopathy in COVID-19 may predispose patients to hypercoagulability-related disorders including thrombosis and even fatal vascular events. Inflammatory storm, uncontrolled inflammation-mediated endothelial injury and renin angiotensin system (RAS) dysregulation are the potential mechanisms. Ongoing efforts made to develop promising therapies provide several potential strategies for hypercoagulability in COVID-19. In this review, we introduce the clinical features of coagulation and the increased vascular thrombotic risk conferred by coagulopathy according to present reports about COVID-19. The potential underlying mechanisms and emerging therapeutic avenues are discussed, emphasizing an urgent need for effective interventions.

Endothelial Dysfunction in COVID-19: Lessons Learned from Coronaviruses

Purpose of Review

To review current literature on endothelial dysfunction with previous coronaviruses, and present available data on the role of endothelial dysfunction in coronavirus disease-2019 (COVID-19) infection in terms of pathophysiology and clinical phenotype

Recent Findings

Recent evidence suggests that signs and symptoms of severe COVID-19 infection resemble the clinical phenotype of endothelial dysfunction, implicating mutual pathophysiological pathways. Dysfunction of endothelial cells is believed to mediate a variety of viral infections, including those caused by previous coronaviruses. Experience from previous coronaviruses has triggered hypotheses on the role of endothelial dysfunction in the pathophysiology of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), which are currently being tested in preclinical and clinical studies.

Summary

Endothelial dysfunction is the common denominator of multiple clinical aspects of severe COVID-19 infection that have been problematic for treating physicians. Given the global impact of this pandemic, better understanding of the pathophysiology could significantly affect management of patients.

Management of anticoagulant-refractory thrombotic antiphospholipid syndrome

Lifelong anticoagulation with warfarin or alternative vitamin K antagonist is the standard anticoagulant treatment for thrombotic antiphospholipid syndrome. Anticoagulant-refractory thrombotic antiphospholipid syndrome can be broadly defined as breakthrough thrombosis while on standard oral anticoagulation treatment and its management is a major challenge given the serious nature of the thrombotic disease observed, which has become refractory to oral anticoagulation. The factors (genetic and cellular) that cause anticoagulant-refractory thrombotic antiphospholipid syndrome are now better understood. However, efforts to use this greater understanding have not yet transformed the capacity to treat it successfully in many patients. In this Viewpoint, we review the factors that are likely to be contributing to the cause of this syndrome and consider how they might be modified or inhibited. We also discuss management, including general strategies to minimise thrombotic risk, intensification of anticoagulation, addition of an antiplatelet agent, adjunctive treatment for thrombosis, immunomodulatory therapy, complement inhibition, vascular options, and future potential therapeutic targets.

COVID-19 Infection and High Intracoronary Thrombus Burden

Coronavirus 2019 (COVID-19) is an acute respiratory disease that has rapidly spread around the world and been declared a global pandemic by the World Health Organization. Emerging evidence demonstrates a strong association with a pro-thrombotic state and we present the first patient admitted with COVID-19 and an inferior ST-segment elevation myocardial infarction (STEMI) with evidence of high intracoronary thrombus burden. We review the mechanism of the high thrombus burden, which may be driven by the significant cytokine storm, endothelial dysfunction, increase risk of coronary plaque rupture and hypercoagulability.

Thrombotic microangiopathy, DIC-syndrome and COVID-19: link with pregnancy prothrombotic state

For last months, humanity has faced a formidable unknown enemy, which is presented as a new coronavirus infection. Despite the fact that the causative agents of new diseases appear at a certain frequency and that the virus SARS-CoV-2 has certain common properties with its predecessors, at the moment we are dealing with a new unknown pathogenesis of the development of severe complications in patients with risk factors. A final understanding of pathological process mechanisms is the goal of the scientific community. Summarizing research data from different countries, it became obvious that in severe cases of viral infection, we are dealing with a combination of the systemic inflammatory response syndrome, disseminated intravascular coagulation and thrombotic microangiopathy (TMA). Thrombotic microangiopathy is represented by a group of different conditions in which thrombocytopenia, hemolytic anemia, and multiple organ failure occur. The article reflects the main types of TMA, pathogenesis and principles of therapy. The main participants in the process are described in detail, including the von Willebrand factor and ADAMTS-13. Based on the knowledge available, as well as new data obtained from patients with COVID-19, we proposed possible models for the implementation of conditions such as sepsis, TMA, and DIC in patients with severe new coronavirus infection. Through a deeper understanding of pathogenesis, it will be possible to develop more effective diagnosis and therapy.

Acute dilated cardiomyopathy in the setting of catastrophic antiphospholipid syndrome and thrombotic microangiopathy: A case series and review

Catastrophic antiphospholipid antibody syndrome (CAPS) is a rare form of antiphospholipid syndrome, an autoimmune condition characterized by vascular thromboses, pregnancy loss, and antiphospholipid (aPL) antibodies. Diagnosis of CAPS relies on thrombosis of at least three different organs systems over 1 week, histopathological evidence of small vessel occlusion, and high aPL antibody titers. In a subset of precipitating circumstances, activation or disruption of endothelial cells in the microvasculature may occur along with cardiomyopathy. We present two cases of CAPS-associated dilated cardiomyopathy at our institution, focusing on disease management, pathophysiology, and treatment. These patients were of Southeastern Asian descent, raising the possibility of genetic polymorphisms contributing to the development of cardiomyopathy. Both met CAPS criteria and both demonstrated clinicopathologic thrombotic microangiopathy (TMA) and complement activation and developed severe dilated cardiomyopathy with shock. Complement activation plays an important role in the development of CAPS and may be important in the pathogenesis of CAPS-associated cardiomyopathy. Clinical suspicion for TMA as a pathophysiologic mechanism of unexplained heart failure in CAPS is important and increased awareness of cardiac side effects is necessary so that early treatment can be initiated to halt further cardiac and systemic complications.

Venous Thromboembolism in COVID-19: Towards an Ideal Approach to Thromboprophylaxis, Screening, and Treatment

Purpose of Review

Novel coronavirus disease 2019 (COVID-19) has been associated with an increased risk of arterial and venous thromboembolic (VTE) diseases. However, there is a limited amount of data regarding the prevention and management of VTE in severe hospitalized COVID-19 patients.

Recent Findings

In this article, we review currently available clinical data, and mechanisms for COVID-associated coagulopathy, and propose algorithms for screening, prevention (including extended-duration prophylaxis), and treatment of these patients.

Summary

Although these recommendations are subject to change given rapidly evolving data, we provide a framework that can guide clinicians in managing thrombotic complications in this challenging condition.

Complement associated microvascular injury and thrombosis in the pathogenesis of severe COVID-19 infection: A report of five cases

Acute respiratory failure and a systemic coagulopathy are critical aspects of the morbidity and mortality characterizing infection with severe acute respiratory distress syndrome-associated coronavirus-2, the etiologic agent of Coronavirus disease 2019 (COVID-19). We examined skin and lung tissues from 5 patients with severe COVID-19 characterized by respiratory failure (n= 5) and purpuric skin rash (n = 3). COVID-19 pneumonitis was predominantly a pauci-inflammatory septal capillary injury with significant septal capillary mural and luminal fibrin deposition and permeation of the interalveolar septa by neutrophils. No viral cytopathic changes were observed and the diffuse alveolar damage (DAD) with hyaline membranes, inflammation, and type II pneumocyte hyperplasia, hallmarks of classic acute respiratory distress syndrome, were not prominent. These pulmonary findings were accompanied by significant deposits of terminal complement components C5b-9 (membrane attack complex), C4d, and mannose binding lectin (MBL)-associated serine protease (MASP)2, in the microvasculature, consistent with sustained, systemic activation of the complement pathways. The purpuric skin lesions similarly showed a pauci-inflammatory thrombogenic vasculopathy, with deposition of C5b-9 and C4d in both grossly involved and normally-appearing skin. In addition, there was co-localization of COVID-19 spike glycoproteins with C4d and C5b-9 in the interalveolar septa and the cutaneous microvasculature of 2 cases examined. In conclusion, at least a subset of sustained, severe COVID-19 may define a type of catastrophic microvascular injury syndrome mediated by activation of complement pathways and an associated procoagulant state. It provides a foundation for further exploration of the pathophysiologic importance of complement in COVID-19, and could suggest targets for specific intervention.

Complement associated microvascular injury and thrombosis in the pathogenesis of severe COVID-19 infection: A report of five cases

Acute respiratory failure and a systemic coagulopathy are critical aspects of the morbidity and mortality characterizing infection with severe acute respiratory distress syndrome-associated coronavirus-2, the etiologic agent of Coronavirus disease 2019 (COVID-19). We examined skin and lung tissues from 5 patients with severe COVID-19 characterized by respiratory failure (n= 5) and purpuric skin rash (n = 3). COVID-19 pneumonitis was predominantly a pauci-inflammatory septal capillary injury with significant septal capillary mural and luminal fibrin deposition and permeation of the interalveolar septa by neutrophils. No viral cytopathic changes were observed and the diffuse alveolar damage (DAD) with hyaline membranes, inflammation, and type II pneumocyte hyperplasia, hallmarks of classic acute respiratory distress syndrome, were not prominent. These pulmonary findings were accompanied by significant deposits of terminal complement components C5b-9 (membrane attack complex), C4d, and mannose binding lectin (MBL)-associated serine protease (MASP)2, in the microvasculature, consistent with sustained, systemic activation of the complement pathways. The purpuric skin lesions similarly showed a pauci-inflammatory thrombogenic vasculopathy, with deposition of C5b-9 and C4d in both grossly involved and normally-appearing skin. In addition, there was co-localization of COVID-19 spike glycoproteins with C4d and C5b-9 in the interalveolar septa and the cutaneous microvasculature of 2 cases examined. In conclusion, at least a subset of sustained, severe COVID-19 may define a type of catastrophic microvascular injury syndrome mediated by activation of complement pathways and an associated procoagulant state. It provides a foundation for further exploration of the pathophysiologic importance of complement in COVID-19, and could suggest targets for specific intervention.

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.

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.

Catastrophic antiphospholipid syndrome: is life-long anticoagulation therapy required?

Catastrophic antiphospholipid syndrome (CAPS) is an unusual complication of antiphospholipid syndrome (APS) occurring in about 1% of patients. If left untreated, mortality can be as high as 50%. Therapy of APS and its complication CAPS is hampered by the lack of validated prospective, controlled, intervention clinical trials, although there is consensus that treatment should include anticoagulation therapy. But there are issues that need to be addressed such as duration and intensity of therapy. The present report describes our experience in 7 patients with CAPS in whom anticoagulation was discontinued after 6 months of therapy. During an average follow-up of 5.5 years, only 2 patients exhibited one episode each of recurrent venous thrombosis, but none of the patients in whom anticoagulation was discontinued experienced recurrent CAPS.Key Points• Discontinuation of long-term anticoagulation therapy in CAPS patients was not followed by recurrence of CAPS.