Novel insights into pathogenesis, diagnosis and treatment of antiphospholipid syndrome

Additional Treatments for High-Risk Obstetric Antiphospholipid Syndrome: a Comprehensive Review

Most investigators currently advocate prophylactic-dose heparin plus low-dose aspirin as the preferred treatment of otherwise healthy women with obstetric antiphospholipid syndrome, whilst women with a history of vascular thrombosis alone or associated with pregnancy morbidity are usually treated with therapeutic heparin doses in association with low-dose aspirin in an attempt to prevent both thrombosis and pregnancy morbidity. However, the protocols outlined above fail in about 20 % of pregnant women with antiphospholipid syndrome. Identifying risk factors associated with pregnancy failure when conventional therapies are utilized is an important step in establishing guidelines to manage these high-risk patients. Some clinical and laboratory risk factors have been found to be related to maternal-foetal complications in pregnant women on conventional therapy. However, the most efficacious treatments to administer to high-risk antiphospholipid syndrome women in addition to conventional therapy in order to avoid pregnancy complications are as yet unestablished. This is a comprehensive review on this topic and an invitation to participate in a multicentre study in order to identify the best additional treatments to be used in this subset of antiphospholipid syndrome patients.

Comparative study between obstetric antiphospholipid syndrome and obstetric morbidity related with antiphospholipid antibodies

BACKGROUND AND OBJECTIVES

To compare clinical, laboratory, treatment and live birth rate data between women with aPL-related obstetric complications (OMAPS) not fulfilling the Sydney criteria and women fulfilling them (OAPS).

MATERIALS AND METHODS

Retrospective and prospective multicentre study. Data comparison between groups from The European Registry on Antiphospholipid Syndrome included within the framework of the European Forum on Antiphospholipid Antibody projects.

RESULTS

338 women were analysed: 247 fulfilled the Sydney criteria (OAPS group) and 91 did not (OMAPS group). In the OMAPS group, 24/91 (26.37%) fulfilled laboratory Sydney criteria (subgroup A) and 67/91 (74.63%) had a low titre and/or non-persistent aPL-positivity (subgroup B). Overall, aPL laboratory categories in OAPS vs. OMAPS showed significant differences: 34% vs. 11% (p<0.0001) for category I, 66% vs. 89% (p<0.0001) for category II. No differences were observed when current obstetric complications were compared (p=0.481). 86.20% of OAPS women were treated vs. 75.82% of OMAPS (p=0.0224), particularly regarding the LDA+LMWH schedule (p=0.006). No differences between groups were observed in live births, gestational, puerperal arterial and/or venous thrombosis.

CONCLUSIONS

Significant differences were found among aPL categories between groups. Treatment rates were higher in OAPS. Both OAPS and OMAPS groups had similarly good foetal-maternal outcomes when treated. The proposal to modify OAPS classification criteria, mostly laboratory requirements, is reinforced by these results.

Pregnancy morbidity in antiphospholipid syndrome: what is the impact of treatment?

Women with persistently circulating antiphospholipid antibodies (aPL) have a higher incidence of recurrent abortions, fetal losses, pre-eclampsia, and placental insufficiency. Current treatment of patients with antiphospholipid syndrome (APS) during pregnancy with heparin and aspirin can act by preventing clot formation and improving live birth rates, but other obstetric morbidities remain high, especially in patients with a history of thrombotic events. In addition to the classical thrombotic placental events, other factors involving inflammation and complement activation seem to play a role in certain complications. In this article, we will review how medications interfere in the pathogenic mechanisms of APS, discuss the impact of current recommended treatment on pregnancy morbidity, and analyze new promising therapies.

Treatment strategies and pregnancy outcomes in antiphospholipid syndrome patients with thrombosis and triple antiphospholipid positivity. A European multicentre retrospective study

Previous thrombosis, diagnosis of systemic lupus erythematosus (SLE) and triple antiphospholipid (aPL) antibody positivity have recently been found to be independent factors associated to pregnancy failure during conventional therapy in women with antiphospholipid syndrome (APS). This study aimed to assess the effect of various treatment strategies on pregnancy outcomes in women with APS and the risk factors for pregnancy failure. One hundred ninety-six pregnancies of 156 patients diagnosed with APS were analysed: 118 (60.2%) of these had previous thrombosis, 81 (41.3%) were diagnosed with SLE, and 107 (54.6%) had triple aPL positivity. One hundred seventy-five (89.3%) were treated with conventional therapies (low-dose aspirin [LDA] or prophylactic doses of heparin + LDA or therapeutic doses of heparin + LDA), while 21 (10.7%) were prescribed other treatments in addition to conventional therapy. The pregnancies were classified into seven risk profiles depending on the patients' risk factors - thrombosis, SLE, and triple aPL positivity - and their single, double or triple combinations. It was possible to find significant difference in outcomes correlated to treatments only in the thrombosis plus triple aPL positivity subset, and logistic regression analysis showed that additional treatments were the only independent factor associated to a favourable pregnancy outcome (odds ratio=9.7, 95% confidence interval=1.1-88.9, p-value<0.05). On the basis of this retrospective study, we found that APS pregnant patients with thrombosis and triple aPL positivity treated with additional therapy had a significant higher live-birth rate with respect to those receiving conventional therapy alone.

The current standing of diagnosis of antiphospholipid syndrome associated with systemic lupus erythematosus

The antiphospholipid syndrome was first described in the early 1980s. The term was first coined to describe patients presenting with recurrent arterial and venous thrombosis or pregnancy complications. Antiphospholipid syndrome was first reported in systemic lupus erythematosus patients, but later on it became obvious that systemic lupus erythematosus is not a necessary condition for its occurrence. It has been shown that antibodies to phospholipids are the main causative agents of the disease, hence its name. The diagnosis of the disease has witnessed a remarkable evolution over the course of the past 25 years. With the observation that clinical parameters would not be enough to accurately diagnose the disease, antiphospholipid antibodies were recognized to play a central role in this regard. The main hindrance to an accurate diagnosis was the lack of standardization between different laboratory parameters that tested for the antiphospholipid antibodies. Lately, a combination of tests has been acknowledged to play a crucial role in diagnosis.

Aspirin for prevention of preeclampsia in lupus pregnancy

Preeclampsia, the onset of hypertension and proteinuria during pregnancy, is a common medical disorder with high maternal and fetal mortality and morbidity. The underlying pathology remains poorly understood and includes inflammation, endothelial dysfunction, and an unbalanced thromboxane A₂/prostacyclin ratio. For women with systemic lupus erythematosus (SLE), particularly those with preexisting renal disease or with active lupus, the risk of developing preeclampsia is up to 14% higher than it is among healthy individuals. The mechanism is still unknown and the data for preventing preeclampsia in lupus pregnancies are rare. Modulating the impaired thromboxane A₂/prostacyclin ratio by administration of low-dose aspirin appears to be the current best option for the prevention of preeclampsia. After providing an overview of the pathogenesis of preeclampsia, preeclampsia in lupus pregnancies, and previous trials for prevention of preeclampsia with aspirin treatment, we recommend low-dose aspirin administration for all lupus patients starting prior to 16 weeks of gestation. Patients with SLE and antiphospholipid syndrome should receive treatment with heparin and low-dose aspirin during pregnancy.

Identification of the binding site for fondaparinux on Beta2-glycoprotein I

Antiphospholipid syndrome (APS) is an autoimmune disease with clinical manifestations of thrombosis and pregnancy complications. Beta2-glycoprotein I (β2GPI) is the major antigen for the APS-related antibodies. Heparin, low-molecular weight heparin and the synthetic pentasaccharide fondaparinux are commonly used for prophylaxis and treatment of thrombosis in patients with antiphospholipid syndrome. These antithrombotic drugs bind and activate antithrombin III to inactivate blood clotting proteases. Heparin and heparin derivatives might have a direct beneficial effect in APS via binding to β2GPI and interfering with prothrombotic properties of β2GPI/antibody complexes. We compared fondaparinux to heparin regarding its ability to bind β2GPI and inhibit the binding of β2GPI/antibody complexes to negatively charged phospholipids and endothelial cells. Although heparin and fondaparinux bind β2GPI at therapeutically relevant doses, neither fondaparinux nor heparin was efficient in inhibition of the binding of β2GPI/antibody complexes to negatively charged phospholipids and endothelial cells. Our studies suggest that these drugs do not act on pathological properties of β2GPI/antibody complexes, emphasizing the need for a new treatment specific for β2GPI-related thrombosis in APS. We observed that the binding interface of fondaparinux on β2GPI does not include the lysine residues known to be critical for binding of heparin. The docking model of the β2GPI complex with fondaparinux is in agreement with multiple experimental observations.

Antiphospholipid syndrome presenting as pulmonary thrombosis and pancreatitis in a young man

The antiphospholipid syndrome and protein-S deficiency are known prothrombotic conditions. The confirmation of the latter in a patient with a recent antiphospholipid syndrome-associated thrombosis may be difficult as protein-S levels are low in a patient in the wake of recent thrombosis, antiphospholipid antibodies themselves may be targeted against protein-S and oral anticoagulation with warfarin may further bring down protein-S levels. We report a case of a 29-year-old man presenting with widespread unprovoked thrombosis in the form of pulmonary thromboembolism, neck vein thrombosis and pancreatitis. He was found to have antiphospholipid syndrome with low protein-S levels on two occasions. He was anticoagulated with heparin and improved over a 24-day hospital stay marred by the development of an exudative pleural effusion.

Conformation of beta2glycoprotein I and its effect on coagulation

β(2)glycoprotein I (β(2)GPI) is the major antigen in the antiphospholipid syndrome. It has been shown that β(2)GPI can adapt to different conformations, a circular, a S-shaped and a J-shaped conformation. In literature anticoagulant properties of β(2)GPI have been indicated, though there is no consensus on how β(2)GPI exerts a certain action. This article will first review existing data on the conformation of β(2)GPI. In addition, we will investigate whether the conformation of β(2)GPI plays a role in in the proposed anticoagulant activity of β(2)GPI. We investigated the effect of native β(2)GPI and phospholipid-bound β(2)GPI on thrombin generation (TG). Native β(2)GPI was found to have no significant effect on the TG regardless of the concentration of tissue factor. On the contrary, β(2)GPI preincubated with phospholipids significantly inhibited TG triggered with low TF concentration, suggesting an effect on the intrinsic pathway. This indicates that native β(2)GPI in circulation obtains its anticoagulant activity in the presence of anionic phospholipids such as activated blood cells thereby serving as an inhibitory modulator in hemostasis.