Recent advances in the antiphospholipid antibody syndrome

PURPOSE OF REVIEW

The antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by recurrent thrombosis and/or obstetrical morbidity in the presence of persistently positive antiphospholipid antibodies. Recent insights into the pathogenesis of APS have begun to elucidate pathophysiology and led to the identification of potential therapeutic interventions. The objective of this review is to examine the advances in this field and highlight the areas of further investigation.

RECENT FINDINGS

Several mechanisms of thrombosis and pregnancy loss in APS have been proposed. These include activation of endothelial cells, monocytes, and platelets, and/or inhibition of natural anticoagulant and fibrinolytic systems by antiphospholipid antibodies. However, in many cases the underlying molecular mechanisms and their relevance to the human disorder remain uncertain. New therapeutic agents such as statins, hydroxychloroquine, rituximab, complement inhibitors, and interventions aimed at disruption of intracellular signaling pathways have shown promise in preclinical and clinical studies.

SUMMARY

Indefinite anticoagulation remains the mainstay of treatment for thrombotic APS. Despite advances in diagnostic techniques, it remains difficult to predict thrombotic risk in asymptomatic patients with antiphospholipid antibodies. Further mechanistic and clinical studies are needed to predict thrombotic risk and develop improved therapies for this devastating illness.

Antiphospholipid Syndrome (APS) - An Update on Clinical Features and Treatment Options

Antiphospholipid syndrome (APS) is an autoantibody disorder characterized by the presence of antiphospholipid (APL) antibodies and heterogeneous clinical manifestations. Patients may present with recurrent thrombosis, obstetric morbidity, cardiac valvular lesions, thrombocytopenia, skin lesions, renal or neurologic abnormalities. We provide a comprehensive review of these diverse clinical features except renal and obstetric complications. Treatment of APS can be challenging as one tries to balance the benefit of anticoagulation therapy in this hypercoagulable state while minimizing the risk of bleeding. We discuss the various therapeutic options including the role of aspirin, warfarin, low molecular weight heparin, new direct thrombin inhibitors, hydroxychloroquine, intravenous gamma globulin, rituximab and others. Lower risk APS patients (i.e. first venous thrombosis) should receive warfarin with a target INR of 2.0-3.0. Higher risk patients (i.e. arterial thrombosis or recurrent venous events) have a target INR of >3.0. Currently, warfarin remains the mainstay in treatment of APS. Because of lack of adequate data, the newer oral direct inhibitors should be considered only when there is a known allergy/ intolerance or poor control with warfarin. Additional vascular and thrombotic risk factors should be aggressively reduced. Further studies involving large number of APS patients, diagnosed according to accepted criteria, are needed to better define the role of newer anticoagulants and other novel therapies.

Rituximab and its therapeutic potential in catastrophic antiphospolipid syndrome

The catastrophic antiphospholipid syndrome (CAPS) is characterized by thrombosis in more than three organs or systems developing over a short period of time. Despite conventional treatment with a combination of anticoagulation plus corticosteroids plus plasma exchange, and/or intravenous immunoglobulin, mortality remains high and some patients suffer from recurrent CAPS episodes. In selected patients, new therapies such as rituximab may be a treatment option. In this review, the rationale for using rituximab in CAPS is discussed.

The antiphospholipid syndrome: still an enigma

Antiphospholipid syndrome (APS) is defined by clinical manifestations that include thrombosis and/or fetal loss or pregnancy morbidity in patients with antiphospholipid antibodies (aPL). Antiphospholipid antibodies are among the most common causes of acquired thrombophilia, but unlike most of the genetic thrombophilias are associated with both venous and arterial thrombosis. Despite an abundance of clinical and basic research on aPL, a unified mechanism that explains their prothrombotic activity has not been defined; this may reflect the heterogeneity of aPL and/or the fact that they may influence multiple pro- and/or antithrombotic pathways. Antiphospholipid antibodies are directed primarily toward phospholipid binding proteins rather than phospholipid per se, with the most common antigenic target being β2-glycoprotein 1 (β2GPI) although antibodies against other targets such as prothrombin are well described. Laboratory diagnosis of aPL depends upon the detection of a lupus anticoagulant (LA), which prolongs phospholipid-dependent anticoagulation tests, and/or anticardiolipin and anti-β2-glycoprotein 1 antibodies. Indefinite anticoagulation remains the mainstay of therapy for thrombotic APS, although new strategies that may improve outcomes are emerging. Preliminary reports suggest caution in the use of direct oral anticoagulants in patients with APS-associated thrombosis. Based on somewhat limited evidence, aspirin and low molecular weight heparin are recommended for obstetrical APS. There remains a pressing need for better understanding of the pathogenesis of APS in humans, for identification of clinical and laboratory parameters that define patients at greatest risk for APS-related events, and for targeted treatment of this common yet enigmatic disorder.

[What's new in internal medicine?]

This article focuses on current trends in various autoimmune diseases of interest for the dermatologist. In the antiphospholipid syndrome, many news: better characterization of the severe disease, involvement of the mTOR pathway in the vasculopathy-induced renal disease, and diversification of the therapeutic approaches: use of mTOR inhibitors and several biologics, new various antiplatelet and anticoagulants. In dermatomyositis, new autoantibodies are better characterized with a good correlation with clinical disease; the results of a large study on genetic predisposition to the disease are available. There are also some therapeutic innovations in systemic sclerosis: benefit of rituximab that seems well tolerated, the results of a large controlled European study about aggressive immunoablative chemotherapy followed by autologous stem cells have just been published, intralesional stem cells injections in the fingers of sclerodactylic patients. Finally, news in celiac disease that is constantly increasing and whose mild forms often have cutaneous manifestations, leading to diagnosis.

Targeted therapy in antiphospholipid syndrome

PURPOSE OF REVIEW

To review novel therapeutic targets that are currently under investigation to develop safer, targeted therapies for antiphsopholipid antibody (aPL)-mediated clinical manifestations.

RECENT FINDINGS

Novel therapeutic options potentially available include anti-CD20 monoclonal antibodies and new-generation anticoagulants (such as direct thrombin and anti-Xa inhibitors). Research focusing on interfering with aPL-mediated cell activation, targeting complement components and the innovative concept of blocking the pathogenic subpopulation of aPL with tailored peptides are currently being explored.

SUMMARY

Antiphospholipid syndrome is an autoimmune disease characterized by thrombosis and pregnancy morbidity occurring in patients persistently positive for aPL. Current therapeutic options remain confined to long-term anticoagulation with vitamin K antagonists. The future holds much promise with the identification of novel potential targets, many of which are currently under investigation. The challenge will be to design prospective randomized controlled clinical trials to provide the evidence necessary to support integration of these therapies into clinical practice.

Antiphospholipid syndrome in renal transplantation

Antiphospholipid syndrome (APS) may occur in isolation or in association with systemic lupus erythematosus (SLE), with the potential to cause renal failure via several distinct pathologies. Renal transplantation in the presence of APS carries a risk of early graft loss from arterial or venous thrombosis, or thrombotic microangiopathy (TMA). Whilst perioperative anticoagulation reduces the risk of large vessel thrombosis, it may result in significant haemorrhage, and its efficacy in preventing post-transplant TMA is uncertain. Here, we report a patient with end-stage kidney disease (ESKD) due to lupus nephritis and APS, in whom allograft TMA developed soon after transplantation despite partial anticoagulation. TMA resolved with plasma exchange-based therapy albeit with some irreversible graft damage and renal impairment. We discuss the differential diagnosis of post-transplant TMA, and current treatment options.

Plasmapheresis in a patient with antiphospholipid syndrome before living-donor kidney transplantation: a case report

Background

Early graft thrombosis and bleeding complications remain important causes of early graft loss following kidney transplantation in patients with antiphospholipid syndrome. Anti-β2-glycoprotein I IgG is a disease-specific antibody in patients with antiphospholipid syndrome. Although plasmapheresis is partially effective for antibody removal, the optimal treatment allowing successful transplantation in patients with antiphospholipid syndrome has not been established. This is the first report of a patient with antiphospholipid syndrome who successfully underwent living-donor kidney transplantation following prophylactic plasmapheresis for removal of anti-β2-glycoprotein I IgG.

Case presentation

A 37-year-old Japanese female was scheduled to undergo a living-donor kidney transplant from her mother. At age 25 years, she experienced renal vein thrombosis, was diagnosed with antiphospholipid syndrome secondary to systemic lupus erythematosus, and was subsequently treated with prednisolone and warfarin. At age 37 years, she was diagnosed with end stage kidney disease, requiring maintenance hemodialysis because of recurrent renal vein thrombosis despite taking anticoagulation therapy. The pretreatment protocol consisted of prophylactic plasmapheresis plus full anticoagulation therapy to counteract the risks of early graft thrombosis. Anticardiolipin and anti-β2-glycoprotein I IgGs were successfully removed by both double filtration plasmapheresis and plasma exchange. The allograft kidney began to function soon after transplantation. No obvious thrombotic complications were observed after transplantation, although anti-β2-glycoprotein I IgG increased to the level observed before plasmapheresis. One year after transplantation, the patient’s kidney function remains stable while receiving anticoagulation therapy as well as a maintenance immunosuppressive regimen.

Conclusion

Prophylactic plasmapheresis plus full anticoagulation therapy may be an effective strategy in patients with antiphospholipid syndrome undergoing living-donor kidney transplantation.

Identification and treatment of APS renal involvement

Renal involvement in antiphospholipid syndrome (APS), either primary or systemic lupus erythematosus (SLE)-related APS, includes renal artery stenosis or thrombosis, renal infarction, renal vein thrombosis and a small-vessel vaso-occlusive nephropathy defined as “antiphospholipid antibody (aPL)-associated nephropathy.” aPL-associated nephropathy is characterized by acute lesions, thrombotic microangiopathy, and chronic lesions such as fibrous intimal hyperplasia, organizing thrombi with or without recanalization, fibrous occlusions of arteries or arterioles and focal cortical atrophy. Systemic hypertension, hematuria, proteinuria (ranging from mild to nephrotic level) and renal insufficiency represent the major clinical manifestations associated with aPL-associated nephropathy. Similar renal histologic and clinical characteristics have been described among all different groups of patients with positive aPL (primary APS, SLE-related APS, catastrophic APS and SLE/non-APS with positive aPL). In patients with aPL-associated nephropathy lesions in the absence of other causes associated with similar histological characteristics, aPL testing needs to be considered.

Obstetrical APS: is there a place for hydroxychloroquine to improve the pregnancy outcome?

The use of the conventional APS treatment (the combination of low-dose aspirin and LMWH) dramatically improved the obstetrical prognosis in primary obstetrical APS (OAPS). The persistence of adverse pregnancy outcome raises the need to find other drugs to improve obstetrical outcome. Hydroxychloroquine is widely used in patients with various autoimmune diseases, particularly SLE. Antimalarials have many anti-inflammatory, anti-aggregant and immune-regulatory properties: they inhibit phospholipase activity, stabilize lysosomal membranes, block the production of several pro-inflammatory cytokines and, in addition, impair complement-dependent antigen-antibody reactions. There is ample evidence of protective effects of hydroxychloroquine in OAPS similar to the situation in SLE arising from in vitro studies of pathophysiological working mechanism of hydroxychloroquine. However, the clinical data on the use of hydroxychloroquine in primary APS are lacking and prospective studies are necessary.

Neurological presentations of the antiphospholipid syndrome: three illustrative cases

The antiphospholipid syndrome (APS) is defined by the association of high titers of antiphospholipid antibodies (aPLs) with thrombotic events and/or obstetrical problems. APS can be isolated or associated with immune system diseases. Several central nervous system (CNS) manifestations have been reported in APS, but are still not included in the international diagnostic criteria. We present here three cases of APS revealed by CNS manifestations. The first patient had a primary APS with stroke, dementia, epilepsy and the "so-called" Liebman-Sacks disease, a subacute thrombotic non-bacterial valvulopathy. The second one developed a primary APS with a Sneddon syndrome, while the third case is a neurolupus-associated APS with subacute encephalopathy, chorea, stroke, and epilepsy. The pathogenesis of the APS is related to both prothrombotic and immunologic effects of the aPLs. Long-term anticoagulation by low-weight heparin or warfarin is currently recommended in APS. We propose to search the presence of aPLs in any case of young adults' stroke, unexplained dementia, and acquired chorea.

[Efficacy and safety of rituximab in the treatment of primary antiphospholipid syndrome: analysis of 24 cases from the bibliography review]

BACKGROUND AND OBJECTIVE

Antiphospholipid syndrome (APS) is characterized by the presence of antiphospholipid antibodies (aPL) and thrombotic and/or obstetric manifestations. Patients without another associated autoimmune disease are considered to have primary APS. Some patients develop thrombosis recurrence despite anticoagulant treatment and some clinical features do not respond to standard therapy. Rituximab may be an alternative in these cases. We review the published scientific evidence on the use of rituximab in the treatment of primary APS.

PATIENTS AND METHODS

Description of a case and review of the literature with descriptive analysis of the demographic, clinical, and immunologic features, treatment and outcome of patients.

RESULTS

We identified 24 patients (15 women [62.5%]), with a mean age of 37.0 ± 13.4 years. The reasons for the use of rituximab were thrombocytopenia (41.7%), skin involvement (33.3%), neurologic and heart valve involvement (12.5%), hemolytic anemia (8.3%) and pulmonary and renal involvement (4.2%). Lupus anticoagulant was present in 72.7% of the cases, the IgG and IgM isotypes of anticardiolipin antibodies in 75 and 50%, respectively, and the anti-β2GPI (IgG e IgM) antibodies in 80% of patients. Thirteen (54.1%) patients received 2 doses of 1,000 mg of rituximab fortnightly, 10 (41.7%) 4 doses of 375 mg/m(2) weekly and one (4.2%) 8 doses of 375 mg/m(2) weekly. Eleven (45.8%) patients presented a complete clinical response, 7 (29.2%) a partial response and 6 (25%) did not respond to rituximab. Four patients with clinical improvement presented with aPL titer decrease and in one patient, aPL levels did not change. In one patient without clinical response, aPL remained positive. A clinical-immunologic dissociation existed in 2 additional cases.

CONCLUSIONS

The results obtained suggest a possible potential benefit of rituximab in the treatment of some clinical manifestations of primary APS such as thrombocytopenia, skin and heart valve involvement.

Activated protein C resistance associated with lupus anticoagulants is a high risk in acute mesenteric venous thrombosis

BACKGROUND

Acute mesenteric venous thrombosis (AMVT) is one of those diseases that cannot be diagnosed by specific symptoms and signs. A high misdiagnosis rate makes AMVT a final diagnosis established by exploratory laparotomy or forensic examinations earlier, during the period when computed tomography was not as efficient as it is now. The main motivation of our research was to improve the diagnosis and treatment by finding the relationship among activated protein C (APC) resistance, antiphospholipid antibodies, and AMVT in the Chinese Han population.

METHODS

APC resistance was tested by activated partial thromboplastin time method in 70 AMVT patients and 75 healthy adult volunteers that excluded hypercoagulable states. Factor V Leiden mutation was analyzed by polymerase chain reaction with restriction fragment length polymorphism. Anticardiolipin antibodies (aCLs) were tested by enzyme-linked immunosorbent assay. A sensitive activated partial thromboplastin time-lupus anticoagulant (LA) test was used according to the guidelines.

RESULTS

Only two samples had factor V Leiden mutation and were excluded. Twenty-one (30.9%) of the 68 AMVT patients had APC resistance. The rate of aCLs positive in AMVT group (13.2%) was significantly increased compared with control group (1.33%; P = .014). The LA-positive rate is significantly different between the AMVT and control group. Among LA-positive patients, the number of APC resistance was much higher than LA-negative patients (P = .000), but aCLs do not have an increased predisposition to APC resistance (P = .85).

CONCLUSIONS

APC resistance associated with LAs is a high risk in AMVT. The way aCL may affect the process of AMVT is not the same as with LA.

The chequered history of the antiphospholipid syndrome

Consideration of the chronology of advances in medical knowledge can provide useful insights into the pathogenesis, diagnosis and treatment of diseases. The antiphospholipid syndrome is an enigmatic disorder and this is reinforced by the misleading associated terminology, the adoption of which results directly from early discoveries relating to the condition. Thus the target antigen of the causative autoantibodies in antiphospholipid syndrome does not reside on phospholipid, and the frequently associated lupus anticoagulant is not restricted to subjects with systemic lupus erythematosus and, paradoxically, despite causing prolongation of clotting times in vitro it is associated with a pronounced tendency to thrombosis. Recognition of the antiphospholipid syndrome has its origins in the identification of subjects with so-called biological false-positive serological reactions for syphilis in the middle years of the last century. Since that time there have been considerable advances in our understanding of the pathogenesis of the disease and the clinical manifestations and associations, improved diagnostic accuracy and an evolving evidence base for optimal therapy. However many gaps in our knowledge remain.

Top 10 clinical research developments in antiphospholipid syndrome

Persistently positive antiphospholipid antibodies (aPL) with thrombosis and/or pregnancy morbidity are a characteristic of antiphospholipid syndrome (APS). Although many challenges and controversies exist regarding APS diagnosis and management, there has been significant progress in APS clinical research in parallel with increased understanding of the pathogenesis. The purpose of this review is to discuss the "top ten" recent clinical developments in APS, including the magnitude of the problem, standardization of aPL tests, predictors of clinical events, diagnostic algorithms, new clinical research collaboration, and potential future treatments, e.g., new anticoagulants and immunosuppressive agents.

14th International Congress on Antiphospholipid Antibodies Task Force Report on Catastrophic Antiphospholipid Syndrome

The 'Task Force on Catastrophic Antiphospholipid Syndrome (CAPS)' was developed on the occasion of the 14th International Congress on Antiphospholipid Antibodies. The objectives of this Task Force were to assess the current knowledge on pathogenesis, clinical and laboratory features, diagnosis and classification, precipitating factors and treatment of this condition in order to address recommendations for future research. This article summarizes the studies analyzed by the Task Force, its recommendations and the future research agenda.

Renal involvement in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease defined by the presence of arterial or venous thrombotic events and/or pregnancy morbidity in patients who test positive for antiphospholipid antibodies (aPLs). APS can be isolated (known as primary APS) or associated with other autoimmune diseases, such as systemic lupus erythematosus (SLE; known as secondary APS). The kidney is a major target organ in APS and renal thrombosis can occur at any level within the vasculature of the kidney (renal arteries, intrarenal arteries, glomerular capillaries and renal veins); events reflect the site and size of the involved vessels. Histological findings vary widely, including ischaemic glomeruli and thrombotic lesions without glomerular or arterial immune deposits on immunofluorescence. Renal prognosis is affected by the presence of aPLs in patients with lupus nephritis and can be poor. In patients with SLE and aPLs, biopsy should be performed because inflammatory and thrombotic lesions require different therapeutic approaches. Renal involvement in patients with definite APS is treated by anticoagulation with long-term warfarin. The range of renal manifestations associated with APS is broadening and, therefore, aPLs have increasing relevance in end-stage renal disease, transplantation and pregnancy.

Revisiting the molecular mechanism of neurological manifestations in antiphospholipid syndrome: beyond vascular damage

Antiphospholipid syndrome (APS) is a multiorgan disease often affecting the central nervous system (CNS). Typically, neurological manifestations of APS include thrombosis of cerebral vessels leading to stroke and requiring prompt initiation of treatment with antiplatelet drugs or anticoagulant therapy. In these cases, alterations of the coagulation system at various levels caused by multiple effects of antiphospholipid antibodies (aPL) have been postulated to explain the vascular damage to the CNS in APS. However, several nonvascular neurological manifestations of APS have progressively emerged over the past years. Nonthrombotic, immune-mediated mechanisms altering physiological basal ganglia function have been recently suggested to play a central role in the pathogenesis of these manifestations that include, among others, movement disorders such as chorea and behavioral and cognitive alterations. Similar clinical manifestations have been described in other autoimmune CNS diseases such as anti-NMDAR and anti-VGCK encephalitis, suggesting that the spectrum of immune-mediated basal ganglia disorders is expanding, possibly sharing some pathophysiological mechanisms. In this review, we will focus on thrombotic and nonthrombotic neurological manifestations of APS with particular attention to immune-mediated actions of aPL on the vascular system and the basal ganglia.

Postural tachycardia syndrome (POTS) and other autonomic disorders in antiphospholipid (Hughes) syndrome (APS)

Background

Antiphospholipid syndrome (APS) is an autoimmune hypercoagulable disorder that has been shown to cause a large number of cardiac and neurological manifestations. Two recent studies have demonstrated abnormalities in cardiovascular autonomic function testing in APS patients without other cardiovascular or autoimmune disease. However, an association between autonomic disorders such as postural tachycardia syndrome and APS has not previously been described.

Methods and results

Data were obtained by retrospective chart review. We identified 15 patients who have been diagnosed with APS and an autonomic disorder. The median age of the patients at the time of data analysis was 39 years. The autonomic disorders seen in these patients included postural tachycardia syndrome, neurocardiogenic syncope and orthostatic hypotension. The majority of patients (14/15) were female and the majority (14/15) had non-thrombotic neurological manifestations of APS, most commonly migraine, memory loss and balance disorder. Many also had livedo reticularis (11/15) and Raynaud’s phenomenon (nine of 15). In some patients, the autonomic manifestations improved with anticoagulation and/or anti-platelet therapy; in others they did not. Two patients with postural tachycardia syndrome who failed to improve with the usual treatment of APS have been treated with intravenous immunoglobulin with significant improvement in their autonomic symptoms.

Conclusion

We believe that autonomic disorders in APS may represent an important clinical association with significant implications for treatment.

Diagnosis and classification of the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by the occurrence of venous and arterial thromboses, often multiple, and recurrent fetal losses, frequently accompanied by a moderate thrombocytopenia, in the presence of antiphospholipid antibodies (aPL). Some estimates indicate that the incidence of the APS is around 5 new cases per 100,000 persons per year and the prevalence around 40-50 cases per 100,000 persons. The aPL are positive in approximately 13% of patients with stroke, 11% with myocardial infarction, 9.5% of patients with deep vein thrombosis and 6% of patients with pregnancy morbidity. The original classification criteria for the APS were formulated at a workshop in Sapporo, Japan, in 1998, during the 8th International Congress on aPL. The Sapporo criteria, as they are often called, were revised at another workshop in Sydney, Australia, in 2004, during the 11th International Congress on aPL. At least one clinical (vascular thrombosis or pregnancy morbidity) and one laboratory (anticardiolipin antibodies, lupus anticoagulant or anti-β2-glycoprotein I antibodies) criterion had to be met for the classification of APS.

14th International Congress on Antiphospholipid Antibodies: task force report on antiphospholipid syndrome treatment trends

Antiphospholipid Syndrome (APS) is characterized by vascular thrombosis and/or pregnancy morbidity occurring in patients with persistent antiphospholipid antibodies (aPL). The primary objective of the APS Treatment Trends Task Force, created as part of the 14th International Congress on aPL, was to systematically review the potential future treatment strategies for aPL-positive patients. The task force chose as future clinical research directions: a) determining the necessity for controlled clinical trials in venous thromboembolism with the new oral direct thrombin or anti-factor Xa inhibitors pending the results of the ongoing rivaroxaban in APS (RAPS) trial, and designing controlled clinical trials in other forms of thrombotic APS; b) systematically analyzing the literature as well as aPL/APS registries, and creating specific registries for non-warfarin/heparin anticoagulants; c) increasing recruitment for an ongoing primary thrombosis prevention trial, and designing secondary thrombosis and pregnancy morbidity prevention trials with hydroxychloroquine; d) determining surrogate markers to select patients for statin trials; e) designing controlled studies with rituximab and other anti-B-cell agents; f) designing mechanistic and clinical studies with eculizumab and other complement inhibitors; and g) chemically modifying peptide therapy to improve the half-life and minimize immunogenicity. The report also includes recommendations for clinicians who consider using these agents in difficult-to-manage aPL-positive patients.

B-Cell Targeted Therapies in Autoimmune Cytopenias and Thrombosis

Ever since the advent of Rituximab and subsequently the emergence of other compounds targeting B cells, a cornucopia of medical applications have been found for this family of compounds. After their establishment as standard of care in many conditions such as rituximab in lymphoma and rheumatoid arthritis, they have been progressively found to aid in the treatment of many other conditions. This area constituted a fertile area of research in the past 12 years. Physicians have investigated the B-cell depleting agents use in cases of autoimmune hematologic cytopenias such as immune thrombocytopenia, Evans syndrome, cold and warm autoimmune hemolytic anemia, and other thrombophilic disorders such as the antiphospholipid syndrome and thrombocytopenic purpura. This chapter presents a historical perspective reviewing the various studies that have been published in this field. In addition, it offers a current assessment of the evidence regarding the use of B-cell depleting agents in the aforementioned conditions.

Treatment of the antiphospholipid syndrome

The antiphospholipid syndrome is characterized by a combination of laboratory findings (i.e., the presence of at least one antiphospholipid antibody) and clinical manifestations (arterial and/or venous thrombosis, obstetrical complications). Long-term oral anticoagulant is recommended to prevent recurrence of both arterial and venous thrombosis, whereas (low molecular weight) heparin plus aspirin is the treatment of choice to prevent further obstetrical complications. In the rare case of catastrophic antiphospholipid syndrome, heparin plus high-dose corticosteroids plus plasma exchange is associated with the highest recovery rate. Some new, non-antithrombotic-based treatments of antiphospholipid syndrome with rituximab, autologous stem cell transplantation, or hydroxychloroquine are also reviewed.

Antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by venous or arterial thrombosis and/or pregnancy morbidity in patients with persistent presence of antiphospholipid antibodies (aPLs). Catastrophic APS is the most severe form of APS, which is associated with rapid development of microvascular thrombosis resulting in multiorgan failure in patients with aPLs. Patients with APS and catastrophic APS are recognized to have a high risk of recurrent thrombosis that can occur despite anticoagulant therapy. Although antithrombotic therapy remains the mainstay of treatment, bleeding manifestations can complicate management and contribute to increased morbidity. Patients with persistently elevated aPL levels, particularly those who exhibit positive testing for lupus anticoagulant, anticardiolipin antibodies, and anti-β2GPI antibodies (triple positivity), appear to be at increased risk for thrombosis and pregnancy complications, whereas isolated positivity for aPLs appears to be associated with low risk. Recognizing that patients with APS have different thrombotic risk profiles may assist clinicians in assessing the risks and benefits of anticoagulation. The optimal type, intensity, and duration of anticoagulation in the treatment of APS remain controversial, particularly for arterial thrombosis and recurrent thrombosis. Future studies that delineate thrombotic risk in APS and evaluate current and novel anticoagulants as well as nonanticoagulant therapies are required.