Diagnosis of antiphospholipid syndrome

Cardiac manifestations in primary antiphospholipid syndrome and their association to antiphospholipid antibodies' types and titers-cross-sectional study of Serbian cohort

OBJECTIVES

Antiphospholipid syndrome (APS) is multisystem autoimmune coagulopathy with antiphospholipid antibodies (aPL) in its ground, manifested as a primary disease (PAPS) or in the setting of other conditions, most commonly systemic lupus erythematosus. The objective of this cross-sectional study was to investigate various cardiac manifestations and their possible relation to aPL type and titer in a Serbian cohort of PAPS patients.

METHODS

A total of 360 PAPS patients were analyzed and aPL analysis included detection of anticardiolipin antibodies (aCL: IgG/IgM), anti-ß2glycoprotein I (ß2GPI: IgG/IgM), and lupus anticoagulant (LA). Cardiac manifestations investigated were valvular lesions (comprehending valvular thickening and dysfunction not related to age and pseudoinfective endocarditis), coronary artery disease (CAD) with specific insight for myocardial infarction (MI), chronic cardiomyopathy (CMP), and acute decompensated heart failure (ADHF) as well as pulmonary hypertension (PH) and intracardiac thrombus presence.

RESULTS

The prevalence of cardiac manifestations overall was 19.6%. There was a strong association between age and the majority of cardiac manifestations, as well as standard atherosclerotic risk factors. aCL IgG-positive patients had a higher prevalence of valvular lesions (p = 0.042). LA presence was significantly related to MI (p = 0.031) and PH (p = 0.044). CMP and ADHF were significantly related to higher titers of aCl IgG (p = 0.033, p = 0.025 respectively). Age and smoking were independent risk predictors for MI in PAPS with meaningful risk for LA positivity (OR 2.567 CI 0.671-9.820 p = 0.168).

CONCLUSIONS

Certain cardiac manifestations in PAPS were related to certain aPL type and/or titer levels, imposing confirmation in prospective studies. Preventive actions, comprehending proper anticoagulant/antithrombotic therapy, and intense action against standard atherosclerotic risk factors are of utmost importance in this group of patients. Key Points • In Serbian patients with primary antiphospholipid syndrome (PAPS), prevalence of non-criteria cardiac manifestations was 19.6% and they were significantly related to certain antiphospholipid antibodies and titers. • Lupus anticoagulant was a meaningful predictor of myocardial infarction, enabling possible risk stratification and proper preventive and therapeutical strategies in this subgroup of PAPS patients. • Patients with high titers of aCL IgG are more prone to acute decompensated heart failure occurence, imposing careful follow-up of these patients • Based on the analysis of the Serbian PAPS cohort, even being non-criterial, cardiology manifestations are significantly present and inclusion of cardiologists in treatment and follow-up of these patients should be implied from the diagnosis establishment.

The mosaic of "seronegative" antiphospholipid syndrome

In the clinical practice it is possible to find patients with clinical signs suggestive of antiphospholipid syndrome (APS), who are persistently negative for the laboratory criteria of APS, that is, anti-cardiolipin antibodies (aCL), anti-β2-GPI antibodies and lupus anticoagulant. Therefore, it was proposed for these cases the term of seronegative APS (SN-APS). In order to detect autoantibodies with different methodological approaches, sera from 24 patients with SN-APS were analysed for anti-phospholipid antibodies using TLC immunostaining, for anti-vimentin/cardiolipin antibodies by enzyme-linked immunosorbent assay (ELISA), and for anti-annexin V and anti-prothrombin antibodies by ELISA and dot blot. Control groups of our study were 25 patients with APS, 18 with systemic lupus erythematosus (SLE), and 32 healthy controls. Results revealed that 13/24 (54.2%) SN-APS sera were positive for aCL (9 of whom were also positive for lysobisphosphatidic acid) by TLC immunostaining, 11/24 (45.8%) for anti-vimentin/cardiolipin antibodies, 3/24 (12.5%) for anti-prothrombin antibodies, and 1/24 (4.2%) for anti-annexin V antibodies. These findings suggest that in sera from patients with SN-APS, antibodies may be detected using "new" antigenic targets (mainly vimentin/cardiolipin) or methodological approaches different from traditional techniques (mainly TLC immunostaining). Thus, SN-APS represents a mosaic, in which antibodies against different antigenic targets may be detected.

Thin-layer chromatography immunostaining in detecting anti-phospholipid antibodies in seronegative anti-phospholipid syndrome

In clinical practice it is possible to find patients with clinical signs suggestive of anti-phospholipid syndrome (APS) who are persistently negative for the routinely used anti-phospholipid antibodies (aPL). Therefore, the term proposed for these cases was seronegative APS (SN-APS). We investigated the clinical usefulness of thin-layer chromatography (TLC) immunostaining in detecting serum aPL in patients presenting clinical features of SN-APS. Sera from 36 patients with SN-APS, 19 patients with APS, 18 patients with systemic lupus erythematosus (SLE), 20 anti-hepatitis C virus (HCV)-positive subjects and 32 healthy controls were examined for aPL using TLC immunostaining. Anti-β(2) -glycoprotein-I, anti-annexin II, anti-annexin V and anti-prothrombin antibodies were tested by enzyme-linked immunosorbent assays (ELISA). Eahy926, a human-derived endothelial cell line, was incubated with immunoglobulin (Ig)G fraction from SN-APS patients and analysis of phospho-interleukin (IL)-1 receptor-associated kinase (IRAK) and phospho-nuclear factor (NF)-κB was performed by Western blot, vascular cell adhesion molecule 1 (VCAM-1) expression by cytofluorimetric analysis and supernatants tissue factor (TF) levels by ELISA. TLC immunostaining showed aPL in 58·3% of SN-APS patients: anti-cardiolipin in 47·2%, anti-lyso(bis)phosphatidic acid in 41·7% and anti-phosphatidylethanolamine in 30·5%. Six of 36 patients showed anti-annexin II. Incubation of Eahy926 cells with IgG from SN-APS induced IRAK phosphorylation, NF-κB activation, VCAM-1 surface expression and TF cell release. TLC immunostaining could identify the presence of aPL in patients with SN-APS. Moreover, the results suggest the proinflammatory and procoagulant effects in vitro of these antibodies.

Influence of antiphospholipid antibody levels and type on thrombotic manifestations: results from the Serbian National Cohort Study

Repeated thromboses are the most frequent clinical manifestation of antiphospholipid syndrome (APS) in the presence of antiphospholipid antibodies (aPL). The objective of this study was to observe the prevalence and localization of thrombosis, and to investigate the importance of aPL type and level for thrombosis-related events in patients diagnosed with APS. These are the first results of patients enrolled in Serbian National Cohort Study which comprises 256 patients: 162 with primary antiphospholipid syndrome (PAPS) and 94 with APS associated with systemic lupus erythematosus (SLE). aPL analysis included detection of aCL (IgG/IgM), β(2)GPI, and lupus anticoagulant. Thrombosis was diagnosed in 119 (46.5%) patients, with higher prevalence in PAPS compared with SLE patients (51.2% and 38.3%, respectively, p = 0.045). There was similar prevalence of arterial thrombosis in PAPS and SLE groups (34.6% and 34%, respectively, p = 0.932) although venous thrombosis was more frequent in PAPS (25.9% and 8.5%, respectively, p = 0.001). Thrombosis was observed in 92 (55.8%) patients who had more than one type of antibody (category I), in 13 (41.9%) patients with category IIa, in 19 (46.3%) patients with category IIb, and in 73 (44.2%) patients with category IIc (p = 0.10). The patients with thrombosis were older than those without thrombosis (49.8 and 39.8 years, respectively, p = 0.001). Overall, older age was a risk factor for thrombosis. The prevalence of venous thrombosis was higher in the PAPS group, but with lower frequency than in literature data. Any aPL type and level is a risk factor for thrombosis.

Antibodies to serine proteases in the antiphospholipid syndrome

It is generally accepted that the major autoantigen for antiphospholipid antibodies (aPL) in the antiphospholipid syndrome (APS) is beta(2)-glycoprotein I (beta(2)GPI). However, a recent study has revealed that some aPL bind to certain conformational epitope(s) on beta(2)GPI shared by the homologous enzymatic domains of several serine proteases involved in hemostasis and fibrinolysis. Importantly, some serine protease-reactive aPL correspondingly hinder anticoagulant regulation and resolution of clots. These results extend several early findings of aPL binding to other coagulation factors and provide a new perspective about some aPL in terms of binding specificities and related functional properties in promoting thrombosis. Moreover, a recent immunological and pathological study of a panel of human IgG monoclonal aPL showed that aPL with strong binding to thrombin promote in vivo venous thrombosis and leukocyte adherence, suggesting that aPL reactivity with thrombin may be a good predictor for pathogenic potentials of aPL.

Vimentin/cardiolipin complex as a new antigenic target of the antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by arterial and venous thrombosis, recurrent abortions, and antiphospholipid antibodies (aPL). However, it is possible to find patients with clinical signs of APS who persistently test negative for aPL (seronegative APS, or SN-APS). The aim of this study was to identify new antigenic target(s) of autoantibodies in APS patients, which may also be recognized in SN-APS. We tested sera from patients with SN-APS with a proteomic approach by analyzing endothelial cell-surface membrane proteins. Sera from SN-APS patients revealed 2 reactive spots corresponding to vimentin, a protein that is shown to bind cardiolipin in vitro. Antivimentin/cardiolipin antibodies were tested in 29 SN-APS patients, 40 APS patients, 30 patients with systemic lupus erythematosus, 30 with rheumatoid arthritis, 30 with venous or arterial thrombosis, and 32 healthy control patients. We observed that not only a large proportion of SN-APS patients but also almost all the APS patients displayed the presence of antivimentin/cardiolipin antibodies. To verify the possible pathogenic role of these autoantibodies, we demonstrated that affinity-purified antivimentin/cardiolipin antibodies induced interleukin receptor-associated kinase phosphorylation and nuclear factor-κB activation in endothelial cells. Our results prompt to identify vimentin as a "new" cofactor for aPL, which may represent a useful tool mainly in SN-APS patients.

Cardiovascular events in patients with antiphospholipid antibodies: strategies of prevention

Antiphospholipid antibodies are a heterogeneous group of auto-antibodies against phospholipids-binding proteins. The antiphospholipid syndrome is an autoimmune disorder characterized by the clinical association of antiphospholipid antibodies with a condition of hypercoagulability that can affect any blood vessel. Involvement of larger vessels, such as arteries or veins, manifests in the form of thrombosis or thromboembolism, whereas involvement of small vessels manifests as thrombotic micro-angiopathy. The antiphospholipid syndrome is also characterized by the presence of recurrent fetal loss. Patients who are persistently positive for antiphospholipid tests, and who have an arterial thrombosis or venous thrombosis history, are at increased risk of recurrence. Oral anticoagulant therapy is the mainstay of treatment for the thrombotic manifestations of the syndrome. Therapy with anticoagulant drugs should be long-term. On the other hand, although the thromboembolic potential of antiphospholipid antibodies has been well documented, there is still no general consensus on the prophylactic treatment of antiphospholipid antibodies carriers who have never developed vascular/obstetric manifestations. The effect of primary prophylaxis in antiphospholipid antibodies positive individuals is not well known and no evidence-based recommendations exist for thrombosis prevention in these individuals. However, the presence of risk factors for thrombosis increases the risk of first event of antiphospholipid antibodies positive patients. In conclusion, there is still much to learn on primary prophylaxis of asymptomatic antiphospholipid antibodies carriers. Hopefully, evidence-based guidelines will be available in the future.

The Euro-Phospholipid project: epidemiology of the antiphospholipid syndrome in Europe

The Euro-Phospholipid project started in 1999 with a multicentre, consecutive and prospective design. A total cohort of 1000 patients with antiphospholipid syndrome (APS), derived from 13 countries (Belgium, Bulgaria, Denmark, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Portugal, Spain and United Kingdom), has been followed since then. This project allowed the identification of the prevalence and characteristics of the main clinical and immunological manifestations at the onset and during the evolution of APS and demonstrated that it is possible to recognize more homogeneous subsets of clinical significance. Patients with APS associated with systemic lupus erythematosus (SLE) had more episodes of arthritis, livedo reticularis and more frequently exhibited thrombocytopenia and leucopenia. Female patients had more episodes of arthritis and livedo reticularis - both connected with the higher prevalence of migraine and SLE-related APS in women, while male patients had more myocardial infarction, epilepsy and lower limb arterial thrombosis. Childhood onset patients presented more episodes of chorea and jugular vein thrombosis, whereas older onset patients were more frequently male and had more strokes and angina pectoris, but less frequently livedo reticularis.

Microarray analysis of autoimmune diseases by machine learning procedures

Microarray-based global gene expression profiling, with the use of sophisticated statistical algorithms is providing new insights into the pathogenesis of autoimmune diseases. We have applied a novel statistical technique for gene selection based on machine learning approaches to analyze microarray expression data gathered from patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (PAPS), two autoimmune diseases of unknown genetic origin that share many common features. The methodology included a combination of three data discretization policies, a consensus gene selection method, and a multivariate correlation measurement. A set of 150 genes was found to discriminate SLE and PAPS patients from healthy individuals. Statistical validations demonstrate the relevance of this gene set from an univariate and multivariate perspective. Moreover, functional characterization of these genes identified an interferon-regulated gene signature, consistent with previous reports. It also revealed the existence of other regulatory pathways, including those regulated by PTEN, TNF, and BCL-2, which are altered in SLE and PAPS. Remarkably, a significant number of these genes carry E2F binding motifs in their promoters, projecting a role for E2F in the regulation of autoimmunity.

Atypical haemolytic uremic syndrome complicated by microangiopathic antiphospholipid-associated syndrome

A 4-year-old boy with an atypical course of haemolytic uremic syndrome (HUS), who developed microangiopathic antiphospholipid-associated syndrome (MAPS) with signs of multiple organ failure during the course of his disease, is reported. Early and aggressive treatment with intravenous gammaglobulin, pulse methylprednisolone and plasmapheresis resulted in an excellent clinical recovery. Our patient showed a concomitant presence of multiple factors that could precipitate atypical HUS, including positive antiphospholipid antibodies, decreased level of factor H and positive anti-ADAMTS-13 antibodies. We suggest that, along with infections, autoimmune conditions or defined genetic abnormalities of complement regulatory genes, MAPS should be considered among the pathogenic mechanisms in patients with atypical HUS.

Sensitive detection of hydrophobic antigens using a novel lipid-aggregate based ELISA

Antibodies against hydrophobic antigens are common in several autoimmune diseases. However, detection of such antibodies by standard immune-assays, such as ELISA, is problematic, in part because of the problems with coating hydrophobic molecules onto polystyrene multi-well plates. We describe a novel method of stably associating hydrophobic antigens to ELISA plates. By mixing the antigen with a hydrophobic molecule containing a hydrophilic anchor, we generate mixed lipid aggregates that can attach to ELISA plates, and are resistant to detergent wash. Using the ganglioside GM-1 and phosphatidylethanolamine conjugated to the hapten DNP (dinitrophenyl) as model antigens, we show that hydrophobic antigens incorporated into mixed lipid aggregates expose their antigenic determinants in a correct configuration. The detection limit of both GM-1 and DNP-PE was considerably improved compared to when these antigens were coated on ELISA plates using organic solvents. Furthermore GM-1 incorporated into mixed lipid aggregates can be detected by specific antibodies in patient serum. The method of incorporating hydrophobic antigens into mixed lipid aggregates for stable association to ELISA plates can presumably be applied to a vast array of hydrophobic antigens, and may well be developed into a large scale screening system for serum reactivity towards different hydrophobic antigens.

Polyarteritis nodosa complicated by antiphospholipid syndrome

Polyarteritis nodosa is a necrotizing vasculitis of small and medium-sized arteries that spares the smallest blood vessels (arterioles, venules, and capillaries). Antiphospholipid syndrome is an autoimmune disorder characterized by venous or arterial thrombosis and/or by fetal losses, associated with antiphospholipid antibodies. The association of both diseases is infrequent. This case report discusses a male patient with a diagnosis of polyarteritis nodosa who, after 7 years of being diagnosed with vasculitis, showed ischemic lesions in his legs associated with high titers of anticardiolipin antibodies, along with angiographic and histologic evidence of thrombosis. Despite immunosuppressive and anticoagulant therapy, his lesions progressed, and both legs had to be amputated.

Antiphospholipid antibodies and hepatitis C virus infection in Iranian thalassemia major patients

Although the precise nature of Antiphospholipid antibodies is still not clearly defined, they are known to have association with thromboembolic events and have been found in hepatitis C virus (HCV) infection. Moreover, high prevalence of HCV infection and thrombotic risk is described in thalassemia. We aimed at investigating the prevalence of anticardiolipin antibodies (aCLAbs), lupus anticoagulant (LA), and their relation with HCV infection in Iranian thalassemic patients. Presence of anti-HCV antibody, serum HCV-RNA, aCLAbs, and LA activity was determined in 131 patients with thalassemia major (male/female: 63/68 aged 3-29 years) registered at thalassemia unit, Dastgheib Hospital, Shiraz, Iran. Sixty-one healthy controls were also included. Anti-HCV antibody was positive in 24 (18.3%), IgG aCLAbs in 56 (42.7%), and LA activity in 9 (6.9%) patients. 87.5% of patients positive for aCLAbs had a low titer of aCLAbs. Although none of the participants had a previous history of thrombosis, higher prevalence of aCLAbs was detected in thalassemic patients compared with controls. No significant difference in the prevalence of aCLAbs was found between HCV-infected and noninfected patients. A high prevalence of aCLAbs, the majority in low titers, was detected in Iranian thalassemic patients irrespective of previous history of thrombosis and presence of HCV infection.

Neurological manifestations of the antiphospholipid syndrome: risk assessments and evidence-based medicine

The antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterised by autoantibody production and vascular thrombosis or pregnancy morbidity. Autoantibodies generated against phospholipid and phospholipid-binding proteins often impair phospholipid-dependent clotting assays (lupus anticoagulants). These autoantibodies activate endothelial cells, platelets and biochemical cascades and can exist in autoimmune disorders such as lupus. Consistently positive antibodies may worsen the severity of thrombo-occlusive disease. The most common neurological manifestations of APS include stroke and transient ischaemic attacks due to arterial thromboses. Antiphospholipid antibodies may cause additional neurological impairments through both vascular and immune mechanisms. Antiaggregant or anticoagulant therapies are indicated for APS-related ischaemic strokes. Treatment regimens for asymptomatic antibody-positive patients and those with refractory disease remain controversial. There is scant literature on neurological APS manifestations in paediatric patients. Assessment of traditional cardiovascular and inherited thrombophilia risk factors is essential in patients with APS. Modifiable risk factors and valvular heart disease may worsen thrombotic and cerebrovascular outcomes. Alternative therapies such as statins, anti-malarials, angiotensin-converting enzyme inhibitors and thrombin inhibitors warrant further research.

Hughes syndrome

Antiphospholipid syndrome, also known as Hughes syndrome, is a recently described entity that mimics symptoms of other diseases such as multiple sclerosis. It is a potentially life-threatening autoimmune disorder where the body produces antibodies directed against phospholipids and phospholipid-binding proteins. Herein a patient with successive ocular vascular events associated with antiphospholipid syndrome is presented.