The systemic nature of the antiphospholipid syndrome

Antiphospholipid syndrome (APS, Hughes' syndrome) is a systemic autoimmune disorder characterized by arterial and/or venous thrombosis and recurrent foetal loss, accompanied by mild to moderate thrombocytopaenia and elevated titres of antiphospholipid antibodies (aPLs): lupus anticoagulant (LAC) and/or anticardiolipin (aCL) antibodies. APS was defined originally in 1983 in systemic lupus erythematosus (SLE) patients, but later it was found that APS can be primary or secondary to other autoimmune diseases or malignancy. During the past 20 years many organs have been reported to be involved in this syndrome and the clinical manifestations are seen in every medical field. Moreover, many aPLs have been found in APS besides aCLs and LACs, which bind to the autoantigen beta-2-glycoprotein I (beta2GPI). Treatment for APS, based on antiplatelet and anticoagulation drugs, is dependent on various parameters, including whether SLE is also present, classical vs non-classical manifestations of the diseases, women with APS based on pregnancy morbidity, the presence of elevated aCL antibody titres in the absence of clinical manifestations, and catastrophic APS.     

Which antiphospholipid antibodies should be measured in the antiphospholipid syndrome?

The results of an analysis of studies published over a 10-year period that addressed the association between antiphospholipid antibodies (aPLs) and thromboembolic events in patients with the antiphospholipid syndrome (APS) are reported. It would appear that lupus anticoagulants are the strongest risk factor for thromboembolic events in aPL-positive patients. Consequently, it is suggested that all patients with clinical manifestations of APS should be tested for these antibodies. On the other hand, the results do not unequivocally show that measurement of anticardiolipin antibodies is of help in defining the thrombotic risk of patients. Furthermore, they only partially support the notion that anti-beta 2-glycoprotein I and antiprothrombin antibodies may be independent risk factors for thrombosis.     

Antiphospholipid syndrome: state of the art with emphasis on laboratory evaluation

Antiphospholipid antibodies (aPLs) are associated with arterial and venous thrombosis, recurrent pregnancy loss and thrombocytopenia. Although aPLs have not yet been conclusively shown to be causal in thrombosis and miscarriage, they are useful laboratory markers for the antiphospholipid syndrome (APS). The syndrome can complicate another autoimmune disease, most commonly systemic lupus erythematosus, but more often occurs alone -- primary APS. Identification of the syndrome is clinically important because of the risk of recurrent thrombosis and the need for antithrombotic therapy in many cases. Diagnosis and treatment of APS represent significant challenges, however, owing to the protean clinical manifestations and associations, limitations of currently available laboratory tests for aPLs, and the lack of clear evidence-based guidance on optimal management.     

The Management of Stroke in Antiphospholipid Syndrome

Ischemic stroke is one of the most common complications of the antiphospholipid syndrome (APS). Because of the relative lack of definitive prospective studies, there is still some debate as to whether the persistent presence of antiphospholipid antibodies (aPLs) increases the risk of recurrent stroke. There is more evidence for aPLs as a risk factor for first stroke. The mechanisms of ischemic stroke are considered to be thrombotic and embolic. APS patients with thrombotic stroke frequently have other, often conventional vascular risk factors. Transesophageal echocardiogram is strongly recommended in APS patients with ischemic stroke because of the high yield of valvular abnormalities. The appropriate management of thrombosis in patients with APS is still controversial because of limited randomized clinical trial data. This review discusses the current evidence for antithrombotic therapy in patients who are aPL positive but do not fulfill criteria for APS, and in APS patients. Alternative and emerging therapies including low molecular weight heparin, new oral anticoagulants (including direct thrombin inhibitors), hydroxychloroquine, statins, and rituximab, are also addressed.     

Antiphospholipid antibodies induce translocation of TLR7 and TLR8 to the endosome in human monocytes and plasmacytoid dendritic cells

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by thromboembolic events and/or fetal loss in the presence of antiphospholipid antibodies (aPLs). The mechanisms underlying the pathogenicity of aPLs are still poorly understood. Here we show that 3 human monoclonal aPLs as well as IgG fractions from patients with the APS increase mRNA expression of the intracellular toll-like receptor (TLR) 7 in plasmacytoid dendritic cells and TLR8 in monocytes. Simultaneously they induce the translocation of TLR7 or TLR8 from the endoplasmic reticulum to the endosome. These effects depend on the uptake of aPLs into the endosome, subsequent activation of endosomal NADPH oxidase, and generation of superoxide. As a consequence cells are dramatically sensitized to ligands for TLR7 and TLR8. This observation delineates a novel signal transduction pathway in innate immunity originating from the endosome. Because the overexpression of TLR7 can also be detected in plasmacytoid dendritic cells from patients with the APS ex vivo, our results provide an explanation for proinflammatory and procoagulant effects of aPLs. Because inappropriate expression of TLR7 has been implicated in the development of systemic autoimmunity, these findings may also be relevant for the understanding of autoimmunity.     

Is Testing for Antiphosphatidylethanolamine Antibodies Clinically Useful?

One of the most intriguing characteristics of the antiphospholipid syndrome (APS) is that diagnosis requires the combined presence of clinical abnormalities (thrombosis and/or miscarriages) and at least one of the following antiphospholipid antibodies: lupus anticoagulant, anticardiolipin, or anti–β2-glycoprotein I. Clinicians occasionally have difficulty making this diagnosis in patients with a clinical picture of APS but without any of the previously mentioned antiphospholipid antibodies. Such a status has been defined as “seronegative APS.” Under these conditions, antiphosphatidylethanolamine antibodies deserve particular attention, as they have been described as being associated with the main clinical events of APS. Thus, this review focuses on issues related to the characteristics of antiphosphatidylethanolamine antibodies, including the nature of antigen targets and their role in homeostasis, the methodologic problems encountered in their detection, and their clinical associations.     

Syndrome des antiphospholipides « séronégatif » : mythe ou réalité ?

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.     

Management of Obstetric Antiphospholipid Syndrome

Recurrent early miscarriages (excluding chromosomal anomalies), late fetal loss, and maternal thrombosis are characteristic of obstetric antiphospholipid syndrome (APS). Obstetric complications such as preeclampsia, fetal growth restriction, premature delivery, and fetal death also occur in higher frequency in APS patients than in the general population. A high-risk obstetric center is needed for proper evaluation of and intervention with pregnant women with APS. Association with lupus carries additional risk of thrombosis when antiphospholipid antibodies (aPLs) are present. Gestational results with live births are improved to about 80% when antithrombotic therapy is used, but failure in 20% to 30% of the cases despite correct treatment with low-dose aspirin with or without heparin reveals new pathways for pregnancy loss in APS and unmet needs. At the moment, there is no recommendation to investigate patients with infertility for the presence of aPLs.     

Placentation, antiphospholipid syndrome and pregnancy outcome

The antiphospholipid antibodies (aPLs) are a diverse group of autoantibodies associated with a pattern of disease known as antiphospholipid syndrome (APS). Pregnancy complications secondary to placental insufficiency are key features of this disease. The mechanisms underlying the placental pathology remain unclear. In this article the process of placentation in healthy and pathological pregnancies is reviewed. The evidence for defective placentation in APS pregnancies and involvement of aPLs in this process is summarized. Finally hypotheses based on the interpretation of these studies are discussed.     

Obstetric and vascular APS: same autoantibodies but different diseases?

Beta2 glycoprotein I (β2GPI)-dependent antiphospholipid antibodies (aPLs) are the main pathogenic autoantibody population and at the same time the laboratory diagnostic tool for the antiphospholipid syndrome (APS). These antibodies are responsible for both the vascular and the obstetric manifestations of the syndrome but the pathogenic mechanisms behind these manifestations are not the same. For example, thrombotic events do not appear to play a major role in APS miscarriages and a direct reactivity of β2GPI-dependent aPLs on decidual and trophoblast cells was reported. A local expression of β2GPI on these tissues was reported both in physiological conditions and in APS women, thus explaining the local tropism of the autoantibodies. The two hit hypothesis was suggested to explain why the vascular manifestations of APS may occur only occasionally in spite of the persistent presence of aPLs. This is not apparently the case for the obstetric variant of the syndrome, making the difference even more striking. A different pathogenesis may also provide the rationale for the well-known fact that the vascular and the obstetric manifestations may occur independently although in a minority of cases.     

Evaluation of the clinical relevance of anti-annexin-A5 antibodies in Chinese patients with antiphospholipid syndrome

A hallmark feature of antiphospholipid syndrome (APS) is the presence of antiphospholipid antibodies (aPLs). Few studies have addressed the clinical relevance of anti-annexin A5 antibodies (aANXA5) in Chinese patients with APS. In this study, we evaluated the clinical performance of aANXA5 in the diagnosis of APS. Sera from 313 subjects were tested, including 170 samples from patients with APS, 104 samples from patients with non-APS diseases as disease controls (DC), and 39 healthy controls (HC). Serum IgG and IgM aANXA5 were determined by ELISA. Overall, the levels of both IgG and IgM aANXA5 were significantly increased in patients with primary APS (PAPS) and APS associated to other diseases (APSAOD) compared with DC and HC. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for IgG and IgM aANXA5 in the diagnosis of APS were 33.5 and 15.3, 99.0 and 99.0, 98.3 and 96.3, and 47.7 and 41.7%, respectively. Significant associations between IgG aANXA5 and arterial thrombotic events (OR, 2.60; 95% CI, 1.44–4.71) and between IgG aANXA5 and venous thrombotic events (OR, 2.80; 95% CI, 1.55–5.06) were identified. No correlations were identified between IgG or IgM aANXA5 and obstetric complications. Our data suggest that aANXA5 could serve as a diagnosis biomarker for patients with APS. More importantly, our data highlighted a potential role of IgG aANXA5 in identifying APS patients with high risk of thrombosis.     

Antiphospholipid Syndrome in Systemic Lupus Erythematosus: Is the Whole Greater Than the Sum of Its Parts?

This article compares the manifestations of systemic lupus erythematosus (SLE) in the presence and absence of antiphospholipid antibodies (aPLs), the hallmark autoantibodies of antiphospholipid syndrome (APS). The combination of SLE and APS appears to be of greater concern than either entity alone. APS complicates SLE by adding a vaso-occlusive factor to the inflammatory component that adversely affects the prognosis of those who have lupus and aPLs. The increase in both morbidity and mortality when both are present has significant therapeutic implications. Anticoagulation may be a safer and more appropriate therapeutic option than instituting a regimen of corticosteroids and immunosuppressive agents with all their attendant adverse effects. It falls upon the physician to clearly define the disease entity and fully evaluate the disease process.     

Apport de la détection des anticorps antiphosphatidylsérine/prothrombine (aPS/PT) dans le diagnostic et la prise en charge du syndrome des antiphospholipides (SAPL)

Antiphospholipid syndrome (APS) is an autoimmune disease and one of the most common causes of acquired thrombophilia. It is characterised by the occurrence of thrombotic or obstetric events associated with the presence of persistent antiphospholipid antibodies. The diagnosis can be challenging, particularly because some biological tests can be disturbed by anticoagulant treatment or inflammation.In the recent years, new antiphospholipid antibodies, including anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT), have emerged but their clinical significance and causality remain uncertain.Biologically, several studies have found a strong correlation between the presence of lupus anticoagulant (LA) and anti-PS/PT antibodies. Clinically, the presence of anti-PS/PT antibodies is associated with an increased risk of thrombosis and obstetric complications. There is also an association with thrombocytopenia, suggesting that the presence of anti-PS/PT antibodies may be associated with more severe clinical APS. Among seronegative APS patients, 6–17% of patients are positive for anti-PS/PT antibodies. This might influence the therapeutic management of patients.This article aims to provide an update on contribution of anti-PS/PT antibodies detection for the diagnosis and management of APS.     

Antiphospholipid antibodies do not a syndrome make

The association of antiphospholipid antibodies (aPLs) with a poor obstetric history and/or thrombotic event is typical of the antiphospholipid syndrome (APS). We report four cases of poor pregnancy outcome where a diagnostic label of APS resulted in delayed recognition of other causes of pregnancy loss. Pregnancy outcomes in these women were not improved with antithrombotic therapy alone. Successful outcomes were achieved only when other causes of recurrent miscarriage were considered and treated.     

The Michael Mason Prize: Pathogenic antiphospholipid antibodies, stressed out antigens and the deployment of decoys

The antiphospholipid syndrome is a common autoimmune cause of vascular thrombosis and recurrent miscarriages. aPLs that target the N-terminal domain [Domain I (DI)] of the phospholipid binding protein ?2-glycoprotein I (?2GPI) represent the key sub-population of aPLs that promote thrombosis. This review describes two research arms relating to the study of this autoantigen. The first arm describes recent novel biochemical and functional insights into the molecular structure of ?2GPI in vivo and how this may be altered in APS. These findings support the emerging hypothesis that redox modification of ?2GPI may be relevant to the pathogenesis of APS and the development of pathogenic anti-?2GPI antibodies. The second arm describes how a recombinant DI peptide engineered using a bacterial expression system was used to delineate the fine immunodominant epitopes on DI that pathogenic anti-?2GPI antibodies target. The epitope was found to be conformational and revolve around arginine (R) 39 within DI. Thus, whole recombinant DI was used in an in vivo mouse model as a novel decoy peptide inhibitor of anti-?2GPI antibodies. DI and a high binding mutant completely abrogated the pathogenic effects of aPL in this murine model, with loss of inhibition of pathogenicity observed upon mutating the residue R39 to serine. This proof-of-principle study supports the ongoing development of recombinant DI as a novel therapeutic inhibitory peptide for patients with APS.     

Pulmonary manifestations of antiphospholipid syndrome: a retrospective analysis of 67 patients

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by arterial and/ or venous thrombosis accompanied by persistently elevated levels of antiphospholipid antibodies (aPLs). The aim of this study is to evaluate the pulmonary manifestations of APS and compare the levels of aPLs in patients with and without pulmonary involvement. We retrospectively reviewed the files of patients with the diagnosis of APS between October 2010 and May 2017. Demographic data, clinical, radiological and laboratory findings were recorded. The study included 67 patients (56 female/11 male) with a mean age of 39?±?13 years. Pulmonary manifestations such as parenchymal and/or vascular involvement were seen in 12 (17.9%) patients. The patients with and without pulmonary manifestations were not significantly different in terms of age (p?=?0.46), comorbidities (p?=?0.48) and APS duration (p?=?0.66). Acute pulmonary thromboembolism (PE) was determined in 11 (16.4%), alveolar hemorrhage in 2 (3%) patients. Four patients with acute PE (36%) developed chronic thromboembolic pulmonary hypertension (CTEPH). One patient developed both CTEPH and diffuse alveolar hemorrhage after acute PE during follow up. Antiphosholipid antibody IgM was highly positive in patients with PE compared to patients without PE (p?=?0.005). Other antibodies and lupus anticoagulant were not significantly different in patients with and without PE. None of the patients were deceased due to pulmonary manifestations of APS. PE was the most common pulmonary manifestation of APS. The development of CTEPH was high among APS patients. Patients with APS should be closely followed for the onset of PE and CTEPH.

     

Antiphospholipid syndrome: Genetic review

The possibility of a genetic predisposition to develop the antiphospholipid syndrome (APS) and to produce anticardiolipin antibodies and lupus anticoagulant has been addressed by family studies and by population studies. Various studies suggest a familial occurrence of anticardiolipin antibodies and lupus anticoagulant, with or without clinical evidence of APS. This familial tendency could be genetically determined. Multiple human leukocyte antigen-DR or -DQ associations with antiphospholipid antibodies have been described. Genetic studies of beta2-glycoprotein-1(GP1) polymorphisms have been determined and valine/leucine polymorphism could be a genetic risk for having anti-beta2-GP1 antibodies and APS. Compared with polymorphism of beta2-GP1 as a genetic risk factor for APS, beta2-GP1 deficiency is not associated with thrombosis and patients with APS usually have normal or somewhat elevated levels of beta2-GP1. The antigen specificity of antiphospholipid antibodies and the pathophysiology of thrombosis in APS are highly heterogeneous and multifactorial.     

Antibody specificity and related clinical features in antiphospholipid syndrome

The concept of antiphospholipid syndrome (APS) has been widely accepted. Antiphospholipid antibodies originally included anticardiolipin antibodies and lupus anticoagulants. However, recent advances have shown that most pathogenic antiphospholipid antibodies are directed to phospholipid binding proteins such as β₂-glycoprotein I (β₂-GPI) and prothrombin. Other candidates for antigens of so-called antiphospholipid antibodies are protein C, protein S, factor V, factor X, annexin V, high and low molecular weight kininogens, and complex with β₂-GPI and oxidized low-density lipoprotein (LDL). These autoantibodies directed to different phospholipid binding proteins are present in the blood stream, and contribute to triggering procoagulant effects on endothelial cells and platelets, leading to thrombosis. The heterogeneity of these antiphospholipid antibodies appears to explain various clinical manifestations in patients with APS. The preliminary classification criteria for definite APS and a general management policy have been proposed, although successful treatment of patients with antiphospholipid antibodies have only been shown by retrospective studies. Further prospective investigations are required to confirm the diagnostic and therapeutic criteria for patients with APS.     

Real-world practice of obstetricians in respect of assays for antiphospholipid antibodies

Objective. The international classification criteria (CC) for definite antiphospholipid syndrome (APS) recommend confirmation of the sustained presence, for at least 12 weeks, of both lupus anticoagulant (LA), as determined by aPTT and RVVT, and anti β2glycoprotein I (β2GPI) or anticardiolipin (aCL) IgG and/or IgM. However, it remains unclear whether obstetricians comply with the aforementioned CC for the diagnosis of APS in daily clinical practice. We performed a nationwide survey to examine the attitudes of Japanese obstetricians toward the use of assays for antiphospholipid antibodies (aPLs).

Methods. A questionnaire was sent to 2,700 obstetric facilities where maternity checkups are carried out. The types of assays conducted for aPLs, ascertainment of persistence of the antibodies for at least 12 weeks, and the cutoff points used for the assays were examined.

Results. Of the facilities surveyed, 61.5% carried out the assay(s) only once. In regard to the type of assay performed, 97.1% carried out the assay for aCL IgG and/or β2GPI-dependent aCL, while 67.9% performed the LA-aPTT and/or LA-RVVT assay. Only 8.8% carried out assays for both LA. As for the cutoff points used, 98% of the facilities used lower cutoff points described in the manufacturers’ manuals rather than the cutoff values recommended in the CC.

Conclusion. Thus, only a limited number of facilities adhered precisely to the CC for the diagnosis of APS. Inappropriate treatment and unnecessary expense are potentially major concerns when facilities overdiagnose APS using lower cutoff points or without ascertaining the persistence of the antibodies for at least 12 weeks. On the other hand, some patients miss the opportunity to be treated for APS because of the absence of testing for LA.