Evaluation of hemostasis and endothelial function in patients with paroxysmal nocturnal hemoglobinuria receiving eculizumab

Complement and the prothrombotic state

In 2007 and 2009 the regulatory approval of the first-in-class complement inhibitor Eculizumab has revolutionized the clinical management of two rare, life-threatening clinical conditions: paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). While being completely distinct diseases affecting blood cells and the glomerulus, PNH and aHUS remarkably share several features in their etiology and clinical presentation. An imbalance between complement activation and regulation at host surfaces underlies both diseases precipitating in severe thrombotic events that are largely resistant to anti-coagulant and/or anti-platelet therapies. Inhibition of the common terminal complement pathway by Eculizumab prevents the frequently occurring thrombotic events responsible for the high mortality and morbidity observed in patients not treated with anti-complement therapy. While many in vitro and ex vivo studies elaborate numerous different molecular interactions between complement activation products and hemostasis, this review focuses on the clinical evidence that links these two fields in humans. Several non-infectious conditions with known complement involvement are scrutinized for common patterns concerning a prothrombotic statues and the occurrence of certain complement activation levels. Next to PNH and aHUS, germline encoded CD59 or CD55 deficiency (the latter causing the disease Complement Hyperactivation, Angiopathic thrombosis, and Protein-Losing Enteropathy; CHAPLE), autoimmune hemolytic anemia (AIHA), (catastrophic) anti-phospholipid syndrome (APS, CAPS) and C3 glomerulopathy are considered. Parallels and distinct features among these conditions are discussed against the background of thrombosis, complement activation, and potential complement diagnostic and therapeutic avenues.

How we('ll) treat paroxysmal nocturnal haemoglobinuria: diving into the future

Paroxysmal nocturnal haemoglobinuria (PNH) is characterized by complement-mediated intravascular haemolysis, severe thrombophilia and bone marrow failure. While for patients with bone marrow failure the treatment follows that of immune-mediated aplastic anaemia, that of classic, haemolytic PNH is based on anti-complement medication. The anti-C5 monoclonal antibody eculizumab has revolutionized treatment, resulting in control of intravascular haemolysis and thromboembolic risk, with improved long-term survival. Novel strategies of complement inhibition are emerging. New anti-C5 agents reproduce the safety and efficacy of eculizumab, with improved patient convenience. Proximal complement inhibitors have been developed to address C3-mediated extra-vascular haemolysis and seem to improve haematological response.

Circulating Endothelial Progenitor Cells and Their Relation to Thrombosis in Paroxysmal Nocturnal Hemoglobinuria and Aplastic Anemia

Thrombosis is a leading cause of morbidity and mortality in paroxysmal nocturnal hemoglobinuria (PNH). Multiple factors are responsible for the thrombotic tendency in these patients. Endothelial progenitorcells (EPCs) originate from primitive hematopoietic stem cells. The EPC count is considered indicative of potential damage and restoration capacity in vascular disease; lower EPC counts are deemed as a risk factor in cardiovascular diseases. We aimed to investigate the count of circulating EPCs in PNH and aplastic anemia (AA) patients receiving eculizumab treatment or not receiving treatment and their relationship with thrombosis. Seventeen PNH patients, 18 AA patients, and 10 healthy volunteers were included in the study. The CD309, CD133, and CD34 antibodies were used to determine counts of circulating EPCs using flowcytometry. EPC levels were compared between the PNH, AA, and healthy control groups. Kolmogorov-Smirnov test. ANOVA, Kruskal-Wallis, and Mann-Whitney U testswereperformedto analyze the quantitative data, while χ2 testing was performed to analyze the qualitative data. Therewasnosignificantdifference in EPC levelsbetweenpatientswithandwithout a history of thrombosis (P > 0.05). Further, therewasnosignificantdifference in thelevels of EPCsbetweenthe AA and PNH groups (P  > 0.05). However, there was a significant positive correlation between levels of EPCs and lactate dehydrogenase (LDH) in multivariate analysis (P < 0.05). The study findings suggest that hemolysis promotes vascular endothelial and new blood vessel formation. Increased EPCs in PNH may indirectly indicatevascular endothelial damage in PNH.

Clinical characteristics and therapeutic outcomes of paroxysmal nocturnal hemoglobinuria patients in Turkey: a multicenter experience

The aim of this study is to collect paroxysmal nocturnal hemoglobinuria (PNH) patient data from hematology centers all over Turkey in order to identify clinical features and management of PNH patients. Patients with PNH were evaluated by a retrospective review of medical records from 19 different institutions around Turkey. Patient demographics, medical history, laboratory findings, and PNH-specific information, including symptoms at the diagnosis, complications, erythrocyte, and granulocyte clone size, treatment, and causes of death were recorded. Sixty patients (28 males, 32 females) were identified. The median age was 33 (range; 17-77) years. Forty-six patients were diagnosed as classic PNH and 14 as secondary PNH. Fatigue and abdominal pain were the most frequent presenting symptoms. After eculizumab became available in Turkey, most of the patients (n = 31/46, 67.4%) were switched to eculizumab. Three patients with classic PNH underwent stem cell transplantation. The median survival time was 42 (range; 7-183 months) months. This study is the first and most comprehensive review of PNH cases in Turkey. It provided us useful information to find out the differences between our patients and literature, which may help us understand the disease.

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.

Markers of Thrombin Generation and Inflammation in Patients with Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) presents with intravascular hemolysis, bone marrow failure and thrombosis. Various studies have reported geographic and ethnic variation in prevalence of thrombosis in PNH. There is limited data on thrombosis in PNH from the Indian subcontinent. In this study we describe disease burden and risk factors for thrombosis in 18 Indian PNH patients. We studied markers of thrombin generation (Thrombin-antithrombin complexes; TAT and D-Dimer), endothelium and platelet activation (soluble P-selectin) and inflammation (interleukin-6; IL-6) in PNH patients and compared their levels with healthy controls. Thrombosis was identified in 17% of PNH patients. TAT, sP-selectin and D-Dimer levels were significantly elevated in PNH patients (TAT: 5.06 ± 1.08 ng/ml; sP-selectin: 80.57 ± 19.5 ng/ml; D-Dimer mean: 936 ng/ml 95% CI 559, 1310) compared to control population (TAT: 3.39 ± 0.769 ng/ml P = 0.016; sP-selectin: 44.67 ± 5.17 ng/ml P = 0.002). Using Youden's J statistic, the cut-off values for TAT and sP-selectin in our cohort of PNH patients were 2.90 ng/ml and 58.41 ng/ml respectively. TAT, sP-selectin and D-Dimer levels were elevated beyond the cut-off values in PNH patients with thrombosis compared to those without thrombosis. A positive correlation was noted between TAT, sP-selectin and D-Dimer levels. Increased TAT, sP-selectin, and D-Dimer levels may indicate impending thrombosis in PNH.

The interaction between the complement system and hemostatic factors

PURPOSE OF REVIEW

To discuss the crosstalk between the complement system and hemostatic factors (coagulation cascade, platelet, endothelium, and Von Willebrand Factor), and the consequences of this interaction under physiologic and pathologic conditions.

RECENT FINDINGS

The complement and coagulation systems are comprised of serine proteases and are genetically related. In addition to the common ancestral genes, the complement system and hemostasis interact directly, through protein-protein interactions, and indirectly, on the surface of platelets and endothelial cells. The close interaction between the complement system and hemostatic factors is manifested both in physiologic and pathologic conditions, such as in the inflammatory response to thrombosis, thrombosis at the inflamed area, and thrombotic complications of complement disorders.

SUMMARY

The interaction between the complement system and hemostasis is vital for homeostasis and the protective response of the host to tissue injury, but also results in the pathogenesis of several thrombotic and inflammatory disorders.

Patients with paroxysmal nocturnal hemoglobinuria demonstrate a prothrombotic clotting phenotype which is improved by complement inhibition with eculizumab

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder, characterized by complement-mediated intravascular hemolysis and thrombosis. The increased incidence of PNH-driven thrombosis is still poorly understood, but unlike other thrombotic disorders, is thought to largely occur through complement-mediated mechanisms. Treatment with a C5 inhibitor, eculizumab, has been shown to significantly reduce the number of thromboembolic events in these patients. Based on previously described links between changes in fibrin clot structure and thrombosis in other disorders, our aim was to investigate clot structure as a possible mechanism of thrombosis in patients with PNH and the anti-thrombotic effects of eculizumab treatment on clot structure. Clot structure, fibrinogen levels and thrombin generation were examined in plasma samples from 82 patients from the National PNH Service in Leeds, UK. Untreated PNH patients were found to have increased levels of fibrinogen and thrombin generation, with subsequent prothrombotic changes in clot structure. No link was found between increasing disease severity and fibrinogen levels, thrombin generation, clot formation or structure. However, eculizumab treated patients showed decreased fibrinogen levels, thrombin generation and clot density, with increasing time spent on treatment augmenting these antithrombotic effects. These data suggest that PNH patients have a prothrombotic clot phenotype due to increased fibrinogen levels and thrombin generation, and that the antithrombotic effects of eculizumab are, in-part, due to reductions in fibrinogen and thrombin generation with downstream effects on clot structure.

Evaluation of endothelial microparticles as a prognostic marker in hemolytic disease of the newborn in China

Objective

This study aimed to evaluate endothelial microparticles (EMPs) as a potential prognostic marker in hemolytic disease of the Chinese neonate.

Methods

We compared 29 newborns with ABO hemolytic disease of the newborn (ABO HDN), 22 newborns with Rh HDN, and 21 healthy newborns with matched mother and infant blood groups (controls). Markers of hemolysis and von Willebrand factor antigen (vWF Ag) were analyzed. EMP (CD144+) levels were measured before and after therapy.

Results

vWF Ag and pretherapy EMP levels were higher in the ABO HDN and Rh HDN groups than in the control group. Additionally, vWF Ag and pretherapy EMP levels were significantly higher in the ABO HDN group than in the Rh HDN group. Posttherapy EMP levels were decreased compared with pretherapy levels in the ABO HDN and Rh HDN groups. Moreover, hemoglobin and indirect bilirubin levels were independently correlated with pretherapy EMP levels in the ABO HDN group.

Conclusion

Our findings indicate that EMP measurement in neonates with HDN may provide a novel method of monitoring possible severe vascular dysfunction in patients in China. An external validation in larger datasets is necessary for further study.

Prediction of thrombosis risk in patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic disease with thrombosis as a major complication. The mechanism of thrombosis and related risk factors in PNH patients are still not well characterized. We retrospectively enrolled 99 patients with newly diagnosed PNH at our institute from 2011 to 2016. According to binary logistic regression model analysis, we first identified four baseline clinical risk factors which may be associated with incidence of thrombosis in the PNH cohort, including PNH clone sizes (fluorescent aerolysin of neutrophil) ≤ 80 (OR 1.056, 95%CI 1.016-1.097, P = 0.005), hemoglobin ≤ 75 g/L (OR 4.202, 95%CI 0.984-17.954, P = 0.053), platelet > 100 × 10⁹/L (OR 6.547, 95%CI 1.490-28.767, P = 0.013) and rs495828 = G (OR 5.243, 95%CI 1.314-20.916, P = 0.019). These independent risk factors were combined together to develop a risk model to evaluate thrombosis risk (AUC = 0.756, 95%CI 0.607-0.905, P < 0.001). Our risk model revealed a higher cumulative incidence of thrombosis and an earlier thrombosis events in PNH patients with high risk (risk score ≥ 23) compared with those with low risk (risk score < 23, P < 0.001 and P = 0.043, respectively). Although with some limitations, we set up a prediction model for thrombosis risk in patients with PNH for the first time, but it needed to be verified in a prospective study with larger patients and longer follow-up time in the future.

Prospective and comparative study of paroxysmal nocturnal hemoglobinuria patients treated or not by eculizumab: Focus on platelet extracellular vesicles

Thrombosis are severe complications of paroxysmal nocturnal hemoglobinuria (PNH), effectively reduced by eculizumab. Extracellular vesicles (EVs) may play a central role. The objective of this study was to assess the procoagulant activity of plasma isolated from PNH patients (treated or not by eculizumab) and to quantify their circulating EVs.We iteratively collected the platelet-free-plasma of 17 PNH patients and 16 matched healthy volunteers, quantified their circulating EVs by flow cytometry and evaluated their procoagulant activity by thrombin generation and STA-Procoag-procoagulant phospholipid (PPL) assays.A significant decrease of EVs from platelets (P = .024) and an increase of the STA-Procoag-PPL clotting time (P = .049) was observed after initiation of eculizumab and up to 11 weeks after. This reduction of prothrombotic biomarkers was not observed with the thrombin generation test due to a lack of sensitivity of this assay. Active hemolysis was observed in 90% of patients and elevated D-dimers in 41% of them. However, no significant difference was observed between patients and control subjects regarding the procoagulant activity, the EVs quantity, or the cellular origin. Lactate dehydrogenase (LDH) levels were lower in eculizumab-treated patients compared to nontreated patients (441 vs 2448 IU/L). D-dimers and LDH decreased after administration of eculizumab (mean decrease of 1307 ng/mL and 4159 IU/L, respectively).These observations suggest a decrease of the phospholipid-dependent procoagulant potential of EVs after eculizumab therapy in PNH patients. TRIAL REGISTRATION:: NUB: B039201214365.

How we treat paroxysmal nocturnal hemoglobinuria: A consensus statement of the Canadian PNH Network and review of the national registry

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by intravascular hemolysis, thrombophilia, and marrow failure. Its phenotype is due to absent or reduced expression of GPI-linked complement regulators and subsequent sensitivity of hematopoietic cells to complement-mediated damage and lysis. Introduction of the terminal complement inhibitor eculizumab drastically improved outcomes in PNH patients; however, despite this improvement, there remain several challenges faced by PNH patients and physicians who care for them. One of the most important is increasing awareness of the heterogeneity with which patients can present, which can lead to significant delays in recognition. Data from the Canadian PNH Registry are presented to demonstrate the variety of presenting symptoms. In Canada, geography precludes consolidation of care to just a few centers, so management is distributed across academic hospitals, linked together as the Canadian PNH Network. The Network over the last several years has developed educational programs and clinical checklists and has worked to standardize access to diagnostics across the country. Herein, we address some of the common diagnostic and therapeutic challenges faced by PNH physicians and give our recommendations. Gaps in knowledge are also addressed, and where appropriate, consensus opinion is provided.

Diagnosis and management of PNH: Review and recommendations from a Belgian expert panel

Despite its considerable morbidity and mortality, paroxysmal nocturnal haemoglobinuria (PNH) is still underdiagnosed. Patients with PNH can suffer from cardiovascular, gastrointestinal, neurological or haematological symptoms and refer to several specialists. The aim of this paper is to review the diagnosis and the management of PNH patients, with the primary focus on identifying high-risk groups. Additionally, the implementation and prognostic value of the defined high-risk groups will be commented on and the management of PNH patients is discussed from a Belgian perspective. Finally, based on the available data, recommendations are provided. Eculizumab is a potent C5 complement inhibitor and reduces intravascular haemolysis and thrombosis in PNH patients and improves their quality of life. As thrombosis is the main cause of death in PNH patients, identifying high-risk PNH patients in need of therapy is essential. Currently, novel complement inhibitors are in development and the first data seem promising. Another challenge in PNH is to identify new markers to assess the thrombotic risk to achieve a better risk-based prophylactic anti-thrombotic management. Finally, because of the low prevalence of the disease, PNH patients should be included in the prospective PNH registry, which will offer new insights on the natural course of the disease and the impact of treatment of PNH.

Prothrombotic mechanisms in patients with congenital p.Cys89Tyr mutation in CD59

BACKGROUND

Thrombosis is the prognostic factor with the greatest effect on survival in patients with paroxysmal nocturnal hemoglobinuria (PNH), who lack dozens of membrane surface proteins. We recently described a primary homozygous Cys89Tyr congenital nonfunctioning CD59 in humans with clinical manifestation in infancy, associated with chronic hemolysis, recurrent strokes, and relapsing peripheral demyelinating neuropathy. Here we investigated hypercoagulability mechanisms characterizing the syndrome.

METHODS

Membrane attack complex (MAC) deposition (anti-SC5b-9) and free hemoglobin (colorimetric assay) were assessed. Platelet activation was identified (anti-CD61, anti-CD62P), and microparticles (MPs) of 0.5-0.9 μm, were characterized (Annexin V, anti-human GlyA, anti-CD15, anti-CD14, anti-CD61). Platelet-monocyte aggregation was assessed with FlowSight.

FINDINGS

2/7 patients (29%) with homozygosity for Cys89Tyr and 6/12 (50%) with any of four described CD59 mutations had recurrent strokes. In plasma samples from four patients carrying identical mutations, MAC deposition was increased on RBCs (p < 0.0003), neutrophils (p < 0.009), and platelets (p < 0.0003). Free-plasma hemoglobin levels were abnormally high, up to 100 mg/dl. Patients with CD59 mutation had RBC-derived MP levels 9-fold higher than those in healthy controls (p < 0.01), and 2-2.5 fold higher than PNH patients (p < 0.09). Leukocyte-activated platelet aggregation was increased (p < 0.0062). Loss of CD59 was shown in the endothelium of these patients.

INTERPRETATION

Nonfunctioning CD59 is a major risk factor for stroke and hypercoagulability. Uncontrolled hemolysis causes massive MP release and endothelial heme damage. MAC attack on unprotected endothelium and platelet activation and aggregation with leukocytes mediate additional mechanisms leading to vascular occlusion. It is suggested that CD59 loss represents a major arterial prothrombotic factor in PNH and additional diseases.

ESCMID Study Group for Infections in Compromised Hosts (ESGICH) Consensus Document on the safety of targeted and biological therapies: an infectious diseases perspective (Soluble immune effector molecules [II]: agents targeting interleukins, immunoglobulins and complement factors)

BACKGROUND

The present review is part of the ESCMID Study Group for Infections in Compromised Hosts (ESGICH) Consensus Document on the safety of targeted and biological therapies.

AIMS

To review, from an Infectious Diseases perspective, the safety profile of agents targeting interleukins, immunoglobulins and complement factors and to suggest preventive recommendations.

SOURCES

Computer-based MEDLINE searches with MeSH terms pertaining to each agent or therapeutic family.

CONTENT

Patients receiving interleukin-1 (IL-1) -targeted (anakinra, canakinumab or rilonacept) or IL-5-targeted (mepolizumab) agents have a moderate risk of infection and no specific prevention strategies are recommended. The use of IL-6/IL-6 receptor-targeted agents (tocilizumab and siltuximab) is associated with a risk increase similar to that observed with anti-tumour necrosis factor-α agents. IL-12/23-targeted agents (ustekinumab) do not seem to pose a meaningful risk of infection, although screening for latent tuberculosis infection may be considered and antiviral prophylaxis should be given to hepatitis B surface antigen-positive patients. Therapy with IL-17-targeted agents (secukinumab, brodalumab and ixekizumab) may result in the development of mild-to-moderate mucocutaneous candidiasis. Pre-treatment screening for Strongyloides stercoralis and other geohelminths should be considered in patients who come from areas where these are endemic who are receiving IgE-targeted agents (omalizumab). C5-targeted agents (eculizumab) are associated with a markedly increased risk of infection due to encapsulated bacteria, particularly Neisseria spp. Meningococcal vaccination and chemoprophylaxis must be administered 2-4 weeks before initiating eculizumab. Patients with high-risk behaviours and their partners should also be screened for gonococcal infection.

IMPLICATIONS

Preventive strategies are particularly encouraged to minimize the occurrence of neisserial infection associated with eculizumab.

Infections associated with the use of eculizumab: recommendations for prevention and prophylaxis

PURPOSE OF REVIEW

Eculizumab inhibits complement effector functions and has significantly impacted the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. However, the risks of potentially life-threatening infections, notably with Neisseria spp. in addition to its cost, are major challenges in clinical practice. In this review, we characterize and summarize the infectious complications reported with the use of eculizumab in the context of its typical and expanding indications.

RECENT FINDINGS

Use of eculizumab is rapidly extending to the fields of transplantation and neurology. Eculizumab has been primarily associated with an increased risk of meningococcal infections. Immunization against its commonest serotypes (ABCWY) is now possible with the advent of the meningococcal B vaccine. A combined ABCWY vaccine is underway. Preventive strategies against breakthrough Neisseria infections should also include chemoprophylaxis. Less is known about the association of eculizumab with other infections as recently reported. Surrogate markers of complement blockade, notably CH50, and eculizumab efficacy may help in the risk assessment of infection.

SUMMARY

Eculizumab has opened new horizons in the treatment of complement-mediated disorders. Prophylactic and immunization strategies against the risk of Nesseria spp. infections are sound and feasible. The use of eculizumab is expanding beyond complement-mediated diseases to transplantation and neurological disorders. Further research is needed to better define and stratify the risk of infection and prevention strategies in patients with the latter indications.

Haemostasis and innate immunity - a complementary relationship: A review of the intricate relationship between coagulation and complement pathways

Coagulation and innate immunity are linked evolutionary processes that orchestrate the host defence against invading pathogens and injury. The complement system is integral to innate immunity and shares numerous interactions with components of the haemostatic pathway, helping to maintain physiological equilibrium. The term 'immunothrombosis' was introduced in 2013 to embrace this process, and has become an area of much recent interest. What is less apparent in the literature however is an appreciation of the clinical manifestations of the coagulation-complement interaction and the consequences of dysregulation of either system, as seen in many inflammatory and thrombotic disease states, such as sepsis, trauma, atherosclerosis, antiphospholipid syndrome (APS), paroxysmal nocturnal haemoglobinuria (PNH) and some thrombotic microangiopathies to name a few. The growing appreciation of this immunothrombotic phenomenon will foster the drive for novel therapies in these disease states, including anticoagulants as immunomodulators and targeted molecular therapies.

Polymorphism of the ABO gene associate with thrombosis risk in patients with paroxysmal nocturnal hemoglobinuria

Thrombosis is one of the most common causes of mortality in Paroxysmal nocturnal hemoglobinuria (PNH), but the predisposing factors for thrombosis are yet to be defined. In this study, we outline the clinical characters and the susceptible genes which lead to thrombotic formation in 104 patients with PNH. The results displayed that the genotypes with minor alleles of rs495828 or rs2519093 in the ABO gene were associated with high risk to thrombus formation (OR 5.95, 95% CI 1.90-18.65 and OR 6.3, 95% CI 2.01-19.79, respectively). Further, the TT haplotype was associated with a significant increased risk of thrombosis (OR=3.25, 95%CI 1.42-7.39). Multivariate regression analysis showed larger PNH clone and genotypes with rs495828/rs2519093 minor allele as independent risk factors for thrombosis in PNH. Some patients who came back for follow-up were tested for the plasma levels of vWF and factor VIII. Patients carrying the rs495828/rs2519093 minor allele had a significant higher level of vWF and factor VIII compared with those carrying the major allele. Therefore, we found for the first time that the rs495828/rs2519093 polymorphism represent an independent prognostic factor in PNH patients for thrombus formation, probably by increasing the vWF and factor VIII.

Extracellular vesicles in renal disease

Extracellular vesicles, such as exosomes and microvesicles, are host cell-derived packages of information that allow cell-cell communication and enable cells to rid themselves of unwanted substances. The release and uptake of extracellular vesicles has important physiological functions and may also contribute to the development and propagation of inflammatory, vascular, malignant, infectious and neurodegenerative diseases. This Review describes the different types of extracellular vesicles, how they are detected and the mechanisms by which they communicate with cells and transfer information. We also describe their physiological functions in cellular interactions, such as in thrombosis, immune modulation, cell proliferation, tissue regeneration and matrix modulation, with an emphasis on renal processes. We discuss how the detection of extracellular vesicles could be utilized as biomarkers of renal disease and how they might contribute to disease processes in the kidney, such as in acute kidney injury, chronic kidney disease, renal transplantation, thrombotic microangiopathies, vasculitides, IgA nephropathy, nephrotic syndrome, urinary tract infection, cystic kidney disease and tubulopathies. Finally, we consider how the release or uptake of extracellular vesicles can be blocked, as well as the associated benefits and risks, and how extracellular vesicles might be used to treat renal diseases by delivering therapeutics to specific cells.

Demyelination, strokes, and eculizumab: Lessons from the congenital CD59 gene mutations

Neurological symptoms of patients with p.Cys89Tyr mutation in the CD59 gene include recurrent peripheral neuropathy resembling Guillain-Barré syndrome, characterized by sensory-motor demyelinating neuropathy with secondary axonal damage and moderate enhancement of the nerve roots on spine MRI, together with recurrent strokes and retinal involvement. Three additional mutations in CD59, leading to loss of function, have been described, and overall, 12/12 (100%) of patients with any mutation presented with neurological symptoms; 11/12 (92%) patients presented with recurrent peripheral neuropathy, 6/12 (50%) with recurrent strokes, and 1/12 (8%) with retinal involvement. We review the possible thrombophilic profile associated with the mutations. In these patients, excessive intravascular hemolysis saturates scavenger mechanisms resulting in free hemoglobin in plasma that irreversibly reacts with nitric oxide to form nitrate and methemoglobin, leading to arterial thrombosis. CD59 loss of function is also one of the major thrombophilic mechanisms in patients with paroxysmal nocturnal hemoglobinuria. We then describe the relationship with demyelination. The lack of CD59 allows uncontrolled complement amplification following low-level spontaneous-, viral-, or post viral-induced complement activation, resulting in severe demyelination in the peripheral nervous system. It is interesting, and certainly encouraging, that after 3 years, following 4 patients with Cys89Tyr mutations who are treated with eculizumab, no strokes occurred and non-permanent neurological insults underwent resolution without any new neurological exacerbations.

Eculizumab decreases the procoagulant activity of extracellular vesicles in paroxysmal nocturnal hemoglobinuria: A pilot prospective longitudinal clinical study

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease characterized by the susceptibility of blood cells to attack by the complement system, inducing extracellular vesicle (EV) production. Thromboembolism is the leading cause of death in this condition. Eculizumab, a humanized monoclonal antibody which inhibits the C5 protein of the complement, reduces the thrombotic risk in PNH.

MATERIALS AND METHOD

We conducted a pilot, prospective, open-label, longitudinal clinical study with six PNH patients treated with eculizumab. The aim was to measure, by flow cytometry, the EVs' production in the patients' platelet-free plasma (PFP) before and during the treatment. We also assessed the procoagulant activity in PFP using STA®-Procoag-PPL and thrombin generation assays (TGA). A high-sensitive version of TGA was also used to study the procoagulant profile induced by the EVs using EVs pelleted from PFP.

RESULTS

We observed a decrease in platelet EV count with eculizumab treatment (p<0.05). STA®-Procoag-PPL assay showed a decrease of the procoagulant profile induced by procoagulant phospholipids (PL) during treatment. These results were not confirmed by TGA on PFP, due to a lack of sensitivity. Thus, we used a high-sensitive version of TGA that enabled us to observe variation in the procoagulant profile induced by the EVs with eculizumab (p<0.05).

CONCLUSIONS

Eculizumab has an impact on the extent of EV production and on the procoagulant profile induced by the procoagulant PL and the EVs. One factor in the antithrombotic action of eculizumab is its ability to decrease EV production and the procoagulant profile induced by PL and EVs.

Hematological disorders and pulmonary hypertension

Pulmonary hypertension (PH), a serious disorder with a high morbidity and mortality rate, is known to occur in a number of unrelated systemic diseases. Several hematological disorders such as sickle cell disease, thalassemia and myeloproliferative diseases develop PH which worsens the prognosis. Associated oxidant injury and vascular inflammation cause endothelial damage and dysfunction. Pulmonary vascular endothelial damage/dysfunction is an early event in PH resulting in the loss of vascular reactivity, activation of proliferative and antiapoptotic pathways leading to vascular remodeling, elevated pulmonary artery pressure, right ventricular hypertrophy and premature death. Hemolysis observed in hematological disorders leads to free hemoglobin which rapidly scavenges nitric oxide (NO), limiting its bioavailability, and leading to endothelial dysfunction. In addition, hemolysis releases arginase into the circulation which converts L-arginine to ornithine, thus bypassing NO production. Furthermore, treatments for hematological disorders such as immunosuppressive therapy, splenectomy, bone marrow transplantation, and radiation have been shown to contribute to the development of PH. Recent studies have shown deregulated iron homeostasis in patients with cardiopulmonary diseases including pulmonary arterial hypertension (PAH). Several studies have reported low iron levels in patients with idiopathic PAH, and iron deficiency is an important risk factor. This article reviews PH associated with hematological disorders and its mechanism; and iron homeostasis and its relevance to PH.

Eculizumab in the management of paroxysmal nocturnal hemoglobinuria: patient selection and special considerations

Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal disorder resulting from somatic mutation in the PIG-A gene leading to a deficiency of the membrane-anchoring molecule glycosylphosphatidylinositol. The lack of expression of two glycosylphosphatidylinositol-anchored proteins involved in the regulation of the complement system renders PNH erythrocytes susceptible to complement-mediated lysis. Clinical manifestations include thromboembolic disease, chronic kidney injury, pulmonary hypertension, smooth muscle dysfunction, and chronic hemolysis. Until recently, treatment was mainly supportive with most patients suffering from significant morbidity and shortened survival compared to age-matched controls. The development of eculizumab, a humanized monoclonal antibody directed against the terminal complement protein C5, has resulted in dramatic improvements of survival and reduction in complications. In this paper, we review some special considerations pertaining to the use of eculizumab for PNH.

Sphingosine 1‑phosphate induced by hypoxia increases the expression of PAI‑1 in HepG2 cells via HIF‑1α

Our group has recently reported that in the immortal human HepG2 liver cell line, sphingosine 1‑phosphate (S1P) increases transcription of plasminogen activator inhibitor type‑1 (PAI‑1), the major physiological inhibitor of fibrinolysis, within 4 h. The present study aimed to elucidate the molecular mechanisms underlying this effect. PAI‑1 expression was measured by reverse transcription‑quantitative polymerase chain reaction and immunoblotting. It was demonstrated that S1P increased PAI‑1 promoter activity but did not increase the activity of promoters lacking the hypoxia responsive element (HRE) 2. In addition, S1P transiently increased the concentration of hypoxia inducible factor (HIF)‑1α, a transcription factor capable of binding to HRE. When HIF‑1α was knocked down, the induction of transcription of PAI‑1 by S1P was no longer observed. Sphingosine kinase (SPHK) activity is increased by hypoxia. It was demonstrated that increases in the concentration of the HIF‑1α protein induced by hypoxia were prevented by treatment with SPHK inhibitor or S1P receptor antagonists. Thus, modification of the induction of HIF‑1α by S1P, leading to increased transcription of PAI‑1, may be an attractive therapeutic target for thrombosis and consequent inhibition of fibrinolysis associated with hypoxia.

Therapeutic complement inhibition in complement-mediated hemolytic anemias: Past, present and future

The introduction in the clinic of anti-complement agents represented a major achievement which gave to physicians a novel etiologic treatment for different human diseases. Indeed, the first anti-complement agent eculizumab has changed the treatment paradigm of paroxysmal nocturnal hemoglobinuria (PNH), dramatically impacting its severe clinical course. In addition, eculizumab is the first agent approved for atypical Hemolytic Uremic Syndrome (aHUS), a life-threatening inherited thrombotic microangiopathy. Nevertheless, such remarkable milestone in medicine has brought to the fore additional challenges for the scientific community. Indeed, the list of complement-mediated anemias is not limited to PNH and aHUS, and other human diseases can be considered for anti-complement treatment. They include other thrombotic microangiopathies, as well as some antibody-mediated hemolytic anemias. Furthermore, more than ten years of experience with eculizumab led to a better understanding of the individual steps of the complement cascade involved in the pathophysiology of different human diseases. Based on this, new unmet clinical needs are emerging; a number of different strategies are currently under development to improve current anti-complement treatment, trying to address these specific clinical needs. They include: (i) alternative anti-C5 agents, which may improve the heaviness of eculizumab treatment; (ii) broad-spectrum anti-C3 agents, which may improve the efficacy of anti-C5 treatment by intercepting the complement cascade upstream (i.e., preventing C3-mediated extravascular hemolysis in PNH); (iii) targeted inhibitors of selective complement activating pathways, which may prevent early pathogenic events of specific human diseases (e.g., anti-classical pathway for antibody-mediated anemias, or anti-alternative pathway for PNH and aHUS). Here we briefly summarize the status of art of current and future complement inhibition for different complement-mediated anemias, trying to identify the most promising approaches for each individual disease.

The role of complement activation in thrombosis and hemolytic anemias

OBJECTIVE

The objective of this study was to describe complement activation in hemostatic and pathologic states of coagulation and in the acquired and congenital hemolytic anemias.

METHODS AND RESULTS

We review published and emerging data on the involvement of the classic, alternative and lectin-based complement pathways in coagulation and the hemolytic anemias. The alternative pathway in particular is always "on," at low levels, and is particularly sensitive to hyper-activation in a variety of physiologic and pathologic states including infection, autoimmune disorders, thrombosis and pregnancy, requiring tight control predicated on a variety of soluble and membrane bound regulatory proteins. In acquired hemolytic anemias such as paroxysmal nocturnal hemoglobinuria (PNH) and cold agglutinin disease (CAD), the complement system directly induces red blood cell injury, resulting in intravascular and extravascular hemolysis. In congenital hemolytic anemias such as sickle cell disease and β-thalassemia, the complement system may also contribute to thrombosis and vascular disease. Complement activation may also lead to a storage lesion in red blood cells prior to transfusion.

CONCLUSION

Complement pathways are activated in hemolytic anemias and are closely linked with thrombosis. In acquired disorders such as PNH and possibly CAD, inhibition of the alternative complement pathway improves clinical outcomes and reduces thrombosis risk. Whether complement inhibition has a similar role in congenital hemolytic anemias apart from the atypical hemolytic-uremic (aHUS)-type thrombotic microangiopathies remains to be determined.

Recent advances in the pathogenesis and treatment of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a very rare disease that has been investigated for over one century and has revealed unique aspects of the pathogenesis and pathophysiology of a hemolytic anemia. PNH results from expansion of a clone of hematopoietic cells that, as a consequence of an inactivating mutation of the X-linked gene PIG-A, are deficient in glycosylphosphatidylinositol (GPI)-linked proteins: since these include the surface membrane complement-regulatory proteins CD55 and CD59, the red cells arising from this clone are exquisitely sensitive to lysis by activated complement. Until a decade ago, the treatment options for PNH were either supportive treatment – often including blood transfusion, anti-thrombosis prophylaxis, and sometimes thrombolytic therapy – or allogeneic bone marrow transplantation. Since 2007, PNH has received renewed and much wider attention because a new form of treatment has become available, namely complement blockade through the anti-C5 monoclonal antibody eculizumab. This brief review focuses on two specific aspects of PNH: (1) response to eculizumab, variability of response, and how this new agent has impacted favorably on the outlook and on the quality of life of patients; and (2) with respect to pathogenesis, new evidence supports the notion that expansion of the PNH clone results from T-cell-mediated auto-immune damage to hematopoietic stem cells, with the GPI molecule as target. Indeed, GPI-specific CD8+ T cells – which have been identified in PNH patients – would spare selectively GPI-negative stem cells, thus enabling them to re-populate the marrow of a patient who would otherwise have aplastic anemia.

Successful Treatment of Ascites using a Denver® Peritoneovenous Shunt in a Patient with Paroxysmal Nocturnal Hemoglobinuria and Budd-Chiari syndrome

A 56-year-old man was diagnosed with aplastic anemia and paroxysmal nocturnal hemoglobinuria at 43 years of age and treatment with cyclosporin A was started. Liver cirrhosis, ascites, and thrombus in the hepatic veins were found at 56 years of age and Budd-Chiari syndrome (BCS) was diagnosed according to angiography findings. He was treated with diuretics and paracentesis was performed several times, but with limited efficacy. A Denver^® peritoneovenous shunt (PVS) was inserted into the right jugular vein; his ascites and renal function improved immediately and his general condition has remained good for 12 months since starting the above treatment regimen. A PVS is a treatment option for ascites due to BCS.

[Paroxysmal nocturnal hemoglobinuria: An unknown cause of thrombosis?]

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disorder of hematopoietic stem cells. Somatic mutation in the phosphatidylinositol glycan class A (PIG-A), X-linked gene, is responsible for a deficiency in glycosphosphatidylinositol-anchored proteins (GPI-AP). The lack of one of the GPI-AP complement regulatory proteins (CD55, CD59) leads to hemolysis. The disease is diagnosed with hemolytic anemia, marrow failure and thrombosis. Thromboembolic complication occurs in 30% of patient after 10 years of follow-up and is the first event in one out of 10 patients. The two most common sites are hepatic and cerebral veins. These locations are correlated with high risk of death. Currently, these data are balanced with the use of a monoclonal antibody (Eculizumab), which has significantly improved the prognosis with a survival similar to general population after 36 months of follow-up. Anticoagulant treatment is recommended after a thromboembolic event but has no place in primary prophylaxis.

Alterations in markers of coagulation and fibrinolysis in patients with Paroxysmal Nocturnal Hemoglobinuria before and during treatment with eculizumab

BACKGROUND

Paroxysmal Nocturnal Hemoglobinuria is characterized by complement-mediated hemolysis and an increased thrombosis risk. Eculizumab, an antibody to complement factor C5, reduces thrombotic risk via unknown mechanisms. Clinical observations suggest that eculizumab has an immediate effect.

OBJECTIVES

A better understanding of the mechanism via which eculizumab reduces thrombotic risk by studying its pharmacodynamic effect on coagulation and fibrinolysis.

METHODS

We measured microparticles (MP), tissue factor (TF) activity, prothrombin fragment 1+2 (F1+2), D-dimer and simultaneously thrombin and plasmin generation in 55 PNH patients. In 20 patients, parameters were compared before and during eculizumab treatment (at 1 and 2hours, 1, 4 and≥12weeks after commencement).

RESULTS

Patients with a history of thrombosis had elevated D-dimers (p=0.02) but not MP. Among patients on anticoagulants, those with thrombosis had higher F1+2 concentrations (p=0.003). TF activity was undetectable in plasma MP. Unexpectedly, thrombin peak height and thrombin potential were significantly lower in PNH patients than in healthy controls. Fibrinolysis parameters were normal. During eculizumab treatment D-dimer levels significantly decreased after 1hour (p=0.008) and remained decreased at≥12weeks (p=0.03). F1+2 (p=0.03) and thrombin peak height (p=0.02) in patients not on anticoagulants significantly decreased at≥week 12. MP remained unchanged.

CONCLUSIONS

Eculizumab induces an immediate decrease of D-dimer levels but not of other markers. The decrease in thrombin peak height and F1+2 suggests that eculizumab reduces thrombin generation. Elevated D-dimer levels in untreated PNH patients with a history of thrombosis suggest possible value in predicting thrombotic risk.

Pathophysiology, diagnosis, and treatment of paroxysmal nocturnal hemoglobinuria: a review

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder of the hematopoietic stem cell that makes blood cells more sensitive to the action of complement. Patients experience intravascular hemolysis, smooth muscle dystonia, renal failure, arterial and pulmonary hypertension, recurrent infectious diseases and an increased risk of notably dreadful thrombotic complications. The diagnosis is made by flow cytometry. Efforts have been recently performed to improve the sensitivity and the standardization of this technique. PNH is frequently associated with aplastic anemia or low-risk myelodysplasia and may be asymptomatic. Management of the classical form of PNH has been dramatically revolutionized by the development of eculizumab, which brings benefits in terms of hemolysis, quality of life, renal function, thrombotic risk, and life expectancy. Prophylaxis and treatment of arterial and venous thrombosis currently remain a challenge in PNH.

Complement the hemostatic system: an intimate relationship

The complement system is important part of our innate immune system and interacts directly with the hemostatic system. Disorders of complement activation or dysregulation resulting in excess complement generation, such as Paroxysmal Nocturnal Hemoglobinuria (PNH), atypical Hemolytic uremic Syndrome (aHUS) and antiphospholipid syndrome (APLS) have been associated with significant thrombophilia. Terminal Complement (C5b-9) deposition on endothelial and tumor cell membranes has also been reported in a variety of cancer. Recent developments in complement inhibition have given us new insights into the mechanism of thrombosis in these disorders.

Eculizumab effect on the hemostatic state in patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by a hypercoagulable state associated with acute hemolysis. Eculizumab is used to reduce the intensity of intravascular hemolysis in PNH patients. The hemostatic status of three patients with PNH was assessed during eculizumab treatment by D-dimer assay and the global assays: thromboelastography (TEG), thrombin generation test (TGТ), and thrombodynamics (TD). In the state of hemolytic crisis before the therapy D-dimer concentration was increased in two patients accompanied by hypercoagulation changes in TEG parameter angle (α). TD parameter the clot growth velocity (V) revealed hypercoagulability while TGT parameter ETP was within the normal range in all patients. The lactate dehydrogenase (LDH) activity decreased during the 8months of eculizumab therapy. The physical health was improved, the frequency of hemolytic crisis decreased. Patients periodically exhibited hypercoagulable state: the mean values α=38±11° (with normal range 20-40°), ETP=1311±442nM·min (with normal range 800-1560nM·min), V=31±4μm/min (with normal range 20-29μm/min). During the eculizumab therapy two patients had the repeated clinical manifestation of acute hemolytic crisis, the parameters of the global tests were increased compared to the previous measurement. The global hemostasis tests TEG, TGT and TD revealed hypercoagulability in patients with PNH during eculizumab therapy.

Complement in paroxysmal nocturnal hemoglobinuria: exploiting our current knowledge to improve the treatment landscape

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder associated with an acquired deficiency in glycophosphatidylinositol-anchor biosynthesis that renders erythrocytes susceptible to complement attack. Intravascular hemolysis via the membrane attack complex is a clinical hallmark of the disease, and C5 blockade is currently the only approved treatment for PNH. However, residual anemia is an emerging observation for many PNH patients receiving anti-C5 treatment. A range of complement-targeted therapeutic approaches, encompassing surface-directed inhibition of C3 convertases, blockade of membrane attack complex assembly or C3 interception using peptidic inhibitors, has yielded promising results and offers leverage for even more effective treatment of PNH. This article discusses recent advances in this rapidly evolving field, integrating critical perspectives from preclinical PNH models and diverse complement modulation strategies with genetic insights and therapy response profiles. It also evaluates the relative efficacy, limitations and benefits afforded by C3 or C5 inhibition in the context of PNH therapeutics.

Intravenous ascorbic acid as an adjuvant to interleukin-2 immunotherapy

Interleukin-2 (IL-2) therapy has been demonstrated to induce responses in 10-20% of advanced melanoma and renal cell carcinoma patients, which translates into durable remissions in up to half of the responsers. Unfortunately the use of IL-2 has been associated with severe toxicity and death. It has been previously observed and reported that IL-2 therapy causes a major drop in circulating levels of ascorbic acid (AA). The IL-2 induced toxicity shares many features with sepsis such as capillary leakage, systemic complement activation, and a relatively non-specific rise in inflammatory mediators such as TNF-alpha, C-reactive protein, and in advanced cases organ failure. Animal models and clinical studies have shown rapid depletion of AA in conditions of sepsis and amelioration associated with administration of AA (JTM 9:1-7, 2011). In contrast to other approaches to dealing with IL-2 toxicity, which may also interfere with therapeutic effects, AA possesses the added advantage of having direct antitumor activity through cytotoxic mechanisms and suppression of angiogenesis. Here we present a scientific rationale to support the assessment of intravenous AA as an adjuvant to decrease IL-2 mediated toxicity and possibly increase treatment efficacy.

CD144+ endothelial microparticles as a marker of endothelial injury in neonatal ABO blood group incompatibility

BACKGROUND

ABO antigens are expressed on the surfaces of red blood cells and the vascular endothelium. We studied circulating endothelial microparticles (EMP) in ABO haemolytic disease of the newborn (ABO HDN) as a marker of endothelial activation to test a hypothesis of possible endothelial injury in neonates with ABO HDN, and its relation with the occurrence and severity of haemolysis.

MATERIAL AND METHODS

Forty-five neonates with ABO HDN were compared with 20 neonates with Rhesus incompatibility (Rh HDN; haemolytic controls) and 20 healthy neonates with matched mother and infant blood groups (healthy controls). Laboratory investigations were done for markers of haemolysis and von Willebrand factor antigen (vWF Ag). EMP (CD144(+)) levels were measured before and after therapy (exchange transfusion and/or phototherapy).

RESULTS

vWF Ag and pre-therapy EMP levels were higher in infants with ABO HDN or Rh HDN than in healthy controls, and were significantly higher in babies with ABO HDN than in those with Rh HDN (p<0.05). In ABO HDN, pre-therapy EMP levels were higher in patients with severe hyperbilirubinaemia than in those with mild and moderate disease or those with Rh HDN (p<0.001). Post-therapy EMP levels were lower than pre-therapy levels in both the ABO HDN and Rh HDN groups; however, the decline in EMP levels was particularly evident after exchange transfusion in ABO neonates with severe hyperbilirubinaemia (p<0.001). Multiple regression analysis revealed that the concentrations of haemoglobin, lactate dehydrogenase and indirect bilirubin were independently correlated with pre-therapy EMP levels in ABO HDN.

DISCUSSION

Elevated EMP levels in ABO HDN may reflect an IgG-mediated endothelial injury parallel to the IgG-mediated erythrocyte destruction and could serve as a surrogate marker of vascular dysfunction and disease severity in neonates with this condition.

The central role of extracellular vesicles in the mechanisms of thrombosis in paroxysmal nocturnal haemoglobinuria: a review

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired disorder of the haematopoietic stem cell that makes blood cells more sensitive to the action of complement. PNH patients experience an increased risk of arterial and venous thrombosis – major causes of death due to this disease. Though many potential interlaced mechanisms are suspected, extracellular vesicles (EVs) of various origins may play a central role. The processes possibly involved are haemolysis, platelet activation, injured endothelial cells and monocyte activation. The impact of transfusion should be evaluated. A better understanding of the mechanisms involved may help to propose guidelines for the prophylaxis and treatment of thrombosis in PNH. In this paper, we propose an updated review of the pathophysiology of the underlying mechanisms of thrombosis associated with PNH, with specific focus on the prominent role of EVs.

Recurrent and Progressive Abdominal Pain and Enteritis in a Japanese Patient with Paroxysmal Nocturnal Hemoglobinuria

This case report describes a young male patient with recurrent abdominal pain persisting for more than 16 months. Clinical investigations showed signs of inflammation and pancytopenia. A diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) was made 9 months after the onset of the abdominal pain, following endoscopic examinations that revealed evidence of a previously unknown hemorrhage. Regular monitoring indicated that the abdominal pain was associated with elevations in lactate dehydrogenase, C-reactive proteins, and D-dimer levels. The patient started treatment with the complement inhibitor eculizumab shortly after it was approved for use in Japanese PNH patients with hemolysis. Resolution of the abdominal pain and normalization of clinical parameters were noted within 3 weeks from treatment initiation.

Anti-Complement Treatment in Paroxysmal Nocturnal Hemoglobinuria: Where we Stand and Where we are Going

Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal, non-malignant, hematological disorder characterized by the expansion of hematopoietic stem cells and progeny mature blood cells which are deficient in some surface proteins, including the two complement regulators CD55 and CD59. PNH is the paradigm of diseases implying complement dysregulation as main pathogenic mechanism; in fact, PNH erythrocytes are uncapable to modulate on their surface physiologic complement activation, which eventually leads to the typical clinical hallmark of PNH - the chronic complement-mediated intravascular anemia. Indeed, due to the lack of CD55 complement is continuously activated on erythrocyte surface, which subsequently enables the terminal lytic complement because of the lack of CD59, finally resulting in erythrocyte lysis. The availability of eculizumab as the first complement inhibitor for clinical use renewed the interest for this rare hematological disease. Indeed, in the last decad the anti-C5 monoclonal antibody has proven effective for the treatment of PNH, resulting in a sustained control of complement-mediated intravascular hemolysis, with a remarkable clinical benefit. Anti-complement treatment allowed transfusion independence in at least half of PNH patients receiving eculizumab, with adequate control of all hemolysis-associated symptoms even in almost all remaining patients. In addition, the risk of thromboembolic events - an other clinical hallmark of PNH, which significantly affects prognosis and survival - seems substantially reduced on eculizumab treatment, apparently resulting in improved survival. Even with all these remarkable effects, eculizumab treatment does not result in hemoglobin normalization, and most patients remain anemic. It has been demonstrated that this is due to persistent activation of the early phases of complement activation (upstream the C5), leading to complement-mediated extravascular hemolysis. Ongoing researches are focusing on possible strategies to improve current anti-complement therapies, aiming to develop second-generation complement therapeutics. Here we review PNH and its complement-mediated pathophysiology, summarizing available data on anti-complement treatment; we'll also discuss recent pathogenic insights which drive the development of novel strategies of complement inhibition.

Cross-sectional validation study of patient-reported outcomes in patients with paroxysmal nocturnal haemoglobinuria

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare, acquired, clonal haemopoietic stem cell disorder that causes chronic intravascular haemolysis, increases the risk of thrombosis and results in significant patient morbidity and mortality. The symptoms of PNH may have a major impact on patient quality of life.

AIMS

To assess patient fatigue and health-related quality of life in 29 patients with PNH using the Functional Assessment of Chronic Illness Therapy Fatigue subscale version 4 (FACIT-Fatigue) and the European Organization for Research and Treatment of Cancer Quality-of-Life Questionnaire-C30, version 3 (EORTC QLQ-C30).

METHODS

Following completion of the questionnaires, patients were interviewed to assess the validity, clarity, relevance and comprehensiveness of the assessments.

RESULTS

Overall, patients considered both the FACIT-Fatigue and EORTC QLQ-C30 instruments to be relevant and adequate in assessing the level of PNH-associated fatigue and other quality-of-life measures. The FACIT-Fatigue questionnaire was considered to be clear and to comprehensively cover PNH-related fatigue. The EORTC QLQ-C30 instrument was considered to be easy to understand, but of an overall lower relevance, although some differences between countries were observed. Patients suggested additional questions that could be incorporated into future EORTC QLQ-C30 versions to make it more relevant to PNH.

CONCLUSIONS

This study confirms the validity of the FACIT-Fatigue and the EORTC QLQ-C30 questionnaires in this patient population and their routine use should be considered in the management of patients with PNH.

A prospective multicenter study of paroxysmal nocturnal hemoglobinuria cells in patients with bone marrow failure

Background

Paroxysmal nocturnal hemoglobinuria (PNH), a rare clonal hematopoietic stem cell disorder, is characterized by chronic, uncontrolled complement activation leading to intravascular hemolysis and an inflammatory prothrombotic state. The EXPLORE study aimed to determine the prevalence of undiagnosed PNH in patients with aplastic anemia (AA), myelodysplastic syndrome (MDS), and/or other bone marrow failure (BMF) syndromes and the effect of PNH clone size on hemolysis.

Methods

Patients, selected from medical office chart reviews, had blood samples collected for hematologic panel testing and for flow cytometry detection of PNH clones.

Results

Granulocyte PNH clones ≥ 1% were detected in 199 of all 5,398 patients (3.7%), 93 of 503 AA patients (18.5%), 50 of 4,401 MDS patients (1.1%), and 3 of 130 other BMF patients (2.3%). Higher-sensitivity analyses detected PNH clones ≥ 0.01% in 167 of 1,746 patients from all groups (9.6%) and in 22 of 1,225 MDS patients (1.8%), 116 of 294 AA patients (39.5%), and four of 54 other BMF patients (7.8%). Among patients with PNH clones ≥ 1%, median clone size was smaller in patients with AA (5.1%) than in those with MDS (17.6%) or other BMF (24.4%), and the percentage of patients with lactate dehydrogenase levels (a marker for intravascular hemolysis) ≥ 1.5 × upper limit of normal was smaller in patients with AA (18.3%) than in those with MDS (42.0%).

Conclusions

These results confirm the presence of PNH clones in high-risk patient groups and suggest that screening of such patients may facilitate patient management and care.

Paroxysmal nocturnal hemoglobinuria: a red clot syndrome

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, nonmalignant disorder of hematopoietic stem cells characterized by hemolysis, diminished hematopoiesis, and thrombophilia. We describe a 65-year-old woman with known PNH and peripheral arterial disease who presented with critical limb ischemia and a nonhealing left foot ulcer. She underwent surgical bypass of a diffusely diseased left superficial femoral artery with autologous reversed saphenous vein graft. Her postoperative course was complicated by wound sepsis and PNH exacerbation with resultant graft thrombosis requiring an above-knee amputation. This case highlights several key concepts relevant to the management of vascular surgery patients with PNH: (1) their predisposition for arterial and venous thrombosis; (2) hypercoagulability despite standard anticoagulation regimens; (3) the role of eculizumab (a monoclonal antibody that inhibits complement activation used to treat PNH) in reducing thrombotic complications and hemolysis; and (4) complications associated with the immunosuppressive effects of eculizumab. We recommend careful monitoring of hemolysis and immunosuppression, aggressive anticoagulation, frequent graft surveillance, and early consultation with hematology.

Paroxysmal nocturnal haemoglobinuria. Experience over a 10 years period

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic, clonal and acquired disorder of the hematopoietic stem cell with a deficiency of all glycophosphatidyl-inositol (GPI) linked proteins. The aim of this retrospective study was to analyse haematological and biochemical data from 152 patients referred to our laboratory for diagnosis of PNH by flow cytometry (FC).

METHODS

Patients and healthy donor (152 and 99 respectively) were studied. Ham, sucrose, lactate dehydrogenase (LDH), Iron, haptoglobin (Hp), blood cell morphology and Kaplow cytochemical stain for leukocyte alkaline phosphatase (LAP) were carried out. GPI-proteins anti-CD55 and CD59 in erythrocytes and the former, plus anti CD16b and CD66b on neutrophils were evaluated by FC.

RESULTS

Anemia and/or leukopenia and/or thrombocytopenia, increased reticulocyte count and LDH were observed in patients with PNH clone. Some of them had dacriocytes, schistocytes. LAP was low. On average, we detected 50% CD59 (-) erythrocytes and 29, 83, 78% CD55/59 (-), CD16b (-), CD66b (-) neutrophils, respectively.

CONCLUSION

Paroxysmal nocturnal hemoglobinuria clone was detected in 20/152 patients. Negative population's percentages were high in patients with classic PNH, Hematimetry, LAP and adequate use of CF contribute to PNH clone detection in the laboratory.