Antiphospholipid antibodies, antiphospholipid syndrome and infections

Serologic laboratory findings in malignancy

Autoantibodies are extremely promising diagnostic and prognostic biomarkers of cancer, and have the potential to promote early diagnosis and to make a large impact by improving patient outcome and decreasing mortality. Moreover, autoantibodies may be useful reagents in the identification of subjects at risk for cancer, bearing premalignant tissue changes. Great efforts are being made in many laboratories to validate diagnostic panels of autoantibodies with high sensitivity and specificity that could be useful in a clinical setting. It is likely that prospective studies of sufficiently large cohorts of patients and controls using high-throughput technology may allow the identification of biomarkers with diagnostic significance, and perhaps of discrete antigen phenotypes with clinical significance. The identification of TAAs may also be essential for the development of anticancer vaccines, because autoantibodies found in cancer sera target molecules involved in signal transduction, cell-cycle regulation, cell proliferation, and apoptosis, playing important roles in carcinogenesis. On this basis, molecular studies of antigenantibody systems in cancer promise to yield valuable information on the carcinogenic process. TAAs identified by serum antibodies in cancer sera can be natural immunogenic molecules, useful as targets for cancer immunotherapy. An important problem encountered in the practice of medicine is the identification of healthy individuals in the general population who unknowingly are at high risk of developing cancer. For the rheumatologist, a related problem is the identification of those patients with rheumatic diseases who are at high risk for developing a malignant process. These problems encountered in the fields of cancer and the rheumatic diseases can in the future be helped by new diagnostic instruments based on antibodies. The need for promoting the early diagnosis of cancer is a recognized major public health problem in need of significant research support for the validation of multiple promising but inconclusive studies, with the intention of producing diagnostic panels of autoantibodies in various types of cancers. Cancer developing in patients with rheumatic diseases is also an important problem requiring prospective longterm follow-up studies of patients with rheumatic diseases, particularly because some of the new biologic therapies seem to increase the cancer risk. It is possible that a panel of autoantibodies common to patients with cancer and the rheumatic diseases may prove to be of value in the identification of those patients with ADs at high risk for neoplasms.

Recent developments in our understanding of the antiphospholipid syndrome

The antiphospholipid syndrome is an autoimmune disease that manifests clinically as recurrent thrombotic complications or foetal losses and serologically with elevated levels of antiphospholipid antibodies in the plasmas of these patients. The term 'antiphospholipid syndrome' is confusing, because the auto-antibodies are not directed against phospholipids but towards a plasma protein, β(2) -glycoprotein I. For many years, the reason why auto-antibodies against β(2) -glycoprotein I were pro-thrombotic was unclear, because β(2) -glycoprotein I seems to be an obsolete protein in our circulation. Human and mice deficient in this protein do not express a clear phenotype. Recent studies on the structure and function of β(2) -glycoprotein I have provided novel insights into the importance of this protein in physiology and its role in the pathology of the antiphospholipid syndrome.

Superior vena cava syndrome – changing etiology in the third millennium

Superior vena cava syndrome (SVCS), is diagnosed following different degrees of central venous system obstruction, which traditionally was caused by infections, tumors or fibrosing mediastinitis. Recently the role of SVC thrombosis secondary to indwelling central venous devices or pacemaker leads as well as different hypercoagulable states have drawn much attention. In the current review we present a 58-year-old female patient who underwent recurrent pacemaker replacements due to recurrent infections. The patient was hospitalized with superior vena cava syndrome and multiple thrombi in the upper body circulation. Additionally the evaluation was conducted for thrombophilia, which revealed the presence of high titers of antiphospholipid antibodies, suggesting the concurrent diagnosis of the antiphospholipid syndrome (APS). This case reflects the changes in the etiology of SVCS, and the need for a comprehensive evaluation of patients, in the search for additional factors that may complicate a pacemaker insertion, such as the presence of antiphospholipid antibodies. We review the relevant literature and highlight the importance for an interdisciplinary approach in the treatment of SVCS nowadays.

Induction of anti-β2 -glycoprotein I autoantibodies in mice by protein H of Streptococcus pyogenes

BACKGROUND

The antiphospholipid syndrome (APS) is characterized by the persistent presence of anti-β(2) -glycoprotein I (β(2) -GPI) autoantibodies. β(2) -GPI can exist in two conformations. In plasma it is a circular protein, whereas it adopts a fish-hook conformation after binding to phospholipids. Only the latter conformation is recognized by patient antibodies. β(2) -GPI has been shown to interact with Streptococcus pyogenes.

OBJECTIVE

To evaluate the potential of S. pyogenes-derived proteins to induce anti-β(2) -GPI autoantibodies.

METHODS AND RESULTS

Four S. pyogenes surface proteins (M1 protein, protein H, streptococcal collagen-like protein A [SclA], and streptococcal collagen-like protein B [SclB]) were found to interact with β(2) -GPI. Only binding to protein H induces a conformational change in β(2) -GPI, thereby exposing a cryptic epitope for APS-related autoantibodies. Mice were injected with the four proteins. Only mice injected with protein H developed antibodies against the patient antibody-related epitope in domain I of β(2) -GPI. Patients with pharyngotonsillitis caused by S. pyogenes who developed anti-protein H antibodies also generated anti-β(2) -GPI antibodies.

CONCLUSIONS

Our study has demonstrated that a bacterial protein can induce a conformational change in β(2) -GPI, resulting in the formation of antiβ(2) -GPI autoantibodies. This constitutes a novel mechanism for the formation of anti-β(2) -GPI autoantibodies.

Antiphospholipid syndrome following toxoplasma retinochoroiditis

PURPOSE

To report a case of antiphospholipid syndrome (APS) following toxoplasma retinochoroiditis.

DESIGN

Interventional case report.

METHOD

The patient was a 24-year-old female with an attack of visual loss due to toxoplasma retinochoroiditis concomitant with branch retinal vein occlusion. Retinitis resolved with anti-toxoplasma treatment. However, a recurrent episode of BRVO and vitreous hemorrhage occurred later.

RESULT

In systemic evaluation, evidence of APS was detected, including high titers of anti-cardiolipin antibody, increased beta-2 microglobulin and anti-toxoplasma IgG antibody, and also low titers of C3, C4, and CH50.

CONCLUSION

Ocular toxoplasmosis should be included in the list of etiologies of secondary APS. Systemic evaluation for detection of APS is a necessary approach to patients with toxoplasma retinochoroiditis and concomitant vascular accident.

HIV-Associated Venous Thromboembolism

HIV infection has been recognized as a prothrombotic condition and this association has now been proven by a large number of studies with a reported VTE frequency among HIV-infected patients ranging from 0.19% to 7,63 %/year. HIV infection is associated with a two to tenfold increased risk of venous thrombosis in comparison with a general population of the same age. Some risk factors demonstrated a strongest association with VTE such as, low CD4⁺ cell count especially in the presence of clinical AIDS, protein S deficiency, and protein C deficiency. Whereas other risk factors are still controversial like protease inhibitor therapy, presence of active opportunistic infections and presence of antiphospholipid antibodies, including anticardiolipin antibodies and lupus anticoagulant. Physicians caring for HIV positive patients should be able to recognize and treat not only the well-known opportunistic infections and malignancies associated with this chronic disease, but also be alert to the less well-known complications such as thromboses. Pulmonary embolism should be included in the differential diagnosis when patients with HIV/AIDS have unexplained dyspnea or hypoxemia. In younger individuals with VTE, especially men, without other identifiable risk factors for VTE, HIV should be considered. Because interactions between warfarin and antiretrovirals is possible, health care providers should also be alert to the potential of dangerously high or low INRs when they are giving anticoagulants to patients with HIV infection who are undergoing antiretroviral therapy.

β(2) -Glycoprotein I: evolution, structure and function

β(2) -Glycoprotein I (β(2) -GPI) is a protein that circulates in blood at high concentrations. The function of β(2) -GPI has long been an enigma. More than 20 years ago, it was discovered that β(2) -GPI is the major antigen for the circulating antibodies in the antiphospholipid syndrome. However, this knowledge has not advanced our understanding of the physiologic role of the protein. In recent years, new insights have suggested an important function of this protein in innate immunity. β(2) -GPI was found to scavenge lipopolysaccharide and was able to clear unwanted anionic cellular remnants such as microparticles from the circulation. The function of β(2) -GPI seems to depend on the structural conformation of the protein, and it has been established that β(2) -GPI can exist in at least two conformations. In this review, we will highlight and summarize the current knowledge on this protein.

Molecular mimicry between virus and host and its implications for dengue disease pathogenesis

Numerous infectious agents may trigger autoimmunity or even result in autoimmune diseases. Several mechanisms have been proposed for pathogen-triggered autoimmunity including molecular mimicry, cryptic antigens, epitope spreading, bystander activation and polyclonal activation. In the case of dengue virus infection which causes serious public health problems, the mechanisms regarding the pathogenesis of dengue hemorrhagic syndrome are not fully resolved. Our previous studies suggest a mechanism of molecular mimicry in which antibodies directed against dengue virus non-structural protein 1 (NS1) cross-react with human platelets and endothelial cells and cause their damage and dysfunction, which may be related to the clinical features of dengue disease. Several cell surface proteins recognized by patient serum samples and anti-NS1 antibodies have been identified. Based on proteomic studies and sequence analysis, the C-terminal region of dengue virus NS1 shows sequence homology with target proteins. In addition, different regions of dengue virus proteins including core, prM, E and NS1 proteins show sequence homology with different coagulatory molecules. As an example, the amino acid sequence 101-106 of E protein (WGNGCG) shows sequence homology with factors XI, X, IX, VII, II (thrombin), plasminogen and tissue plasminogen activator. Furthermore, single chain variable region against NS1 can interfere with fibrin formation, which leads to prolonged thrombin time. We hypothesize that molecular mimicry between dengue virus proteins and coagulatory molecules may induce cross-reactive autoantibodies that can interfere with coagulation activation. A molecular mimicry pathogenesis for dengue disease which involves cross-reactivity of dengue virus with human endothelial cells, platelets and coagulatory molecules is proposed.

Multiple thromboemboli associated to two occult tumors: a case mimicking catastrophic antiphospholipid syndrome

Thromboembolic events tend to arise during the natural lifetime of tumors. However, multiple thromboemboli mimicking catastrophic antiphospholipid syndrome is quite rare as a first manifestation of a tumor. Herein we describe the case of a 51-year old woman that presented with multiple thromboemboli affecting her brain, lung and kidneys. Despite bolus administration of corticosteroids, anticoagulant therapy and immunoglobulin infusion treatment, the patient died. She had suffered from two occult tumors, which could not be identified premortem: a lung adenocarcinoma and an intrahepatic cholangiocarcinoma. This case underscores the importance of determining the underlying etiology behind multiple thromboemboli. The most important prognostic factor is rapid initiation of treatment of the multiple thromboemboli, emphasizing treatment of their etiology.

Characterization of antiphospholipid antibodies in chronic hepatitis B infection

BACKGROUND

Many infections are associated with antiphospholipid antibodies (aPLs). The purpose of this study was to investigate the prevalence, persistence, clinical significance, and characteristics of aPLs in hepatitis B virus (HBV)-infected patients.

METHODS

This study included 143 patients with HBV infection and 32 healthy individuals as controls. The presence of anticardiolipin antibodies (aCL Ab), anti-β(2)-glycoprotein I antibodies (β(2)GPI Ab), and lupus anticoagulant (LA) was assessed.

RESULTS

The total prevalence of aPLs in HBV-infected patients was 12.6% (18 of 143). Of these 18 patients, 15 had low to medium titers of aCL Ab (10 with IgM, 4 with IgG, and 1 with both isotypes). β(2)GPI Ab and LA were detected in 3 (2.1%) and 2 (1.4%) patients with HBV infection, respectively. In follow-up specimens from 14 patients with elevated levels of aCL Ab or β(2)GPI Ab, 10 (71.4%) showed the persistent presence of aPLs. No clinical manifestations related to aPLs were identified.

CONCLUSION

In HBV-infected patients, the most frequently detected antiphospholipid antibodies were IgM aCL Ab, which have a weak association with the clinical manifestations of APS. Unlike the transient presence reported for other infection-associated aPLs, most aPLs were persistently detected over a 12-week period in patients with HBV infection.

The anti-cyclic citrullinated peptide response in tuberculosis patients is not citrulline-dependent and sensitive to treatment

Introduction

Patients with tuberculosis (TB) frequently produce anti-citrullinated protein antibodies (ACPA). The objective of this study is to characterize the citrulline-dependence of the ACPA reactivity in sera of patients with mycobacterium infections.

Methods

Serum samples of 134 patients with untreated mycobacterium infections (122 TB, 12 nontuberculous mycobacterium) were tested for antibodies against both the citrullinated (Cit) and the non-citrullinated (Arg) form of 2 cyclic synthetic peptides. In 33 patients, a follow-up sample was tested six months after starting anti-mycobacterial drugs.

Results

A substantial proportion of patients with mycobacterial infections demonstrated antibodies against 0401Cit, 0401Arg, 0722Cit and 0722Arg. Fourteen patients demonstrated anti-0401Cit, 83 anti-0401Arg, 22 anti-0722Cit and 61 anti-0722Arg, while none of these antibodies were detected in the 20 healthy controls. All the patients but one, who were anti-0401Cit and anti-0722Cit positive, demonstrated reactivity against the respective Arg peptide. In the subset of 33 patients with a follow-up test six months after starting treatment, the mean levels of antibodies to 0401Cit, 0401Arg, 0722Cit and 0722Arg significantly decreased after treatment. All the patients who were anti-0401Cit and anti-0722Cit positive turned negative after treatment. The presence of anti-0401Cit/Arg and anti-0722Cit/Arg was found to be significantly correlated with the presence of HIV.

Conclusions

ACPA may be found in patients with TB. In most of the cases, the reactivity is citrulline independent. A positive cyclic citrullinated peptide (CCP) test in these patients should therefore be interpreted with care, and preferably followed by a control ELISA with a non-citrullinated antigen.

The cardiac manifestations of antiphospholipid syndrome and their echocardiographic recognition

Antiphospholipid syndrome is an autoimmune disorder characterized by the presence of antiphospholipid antibodies, hypercoagulability, vascular thrombosis, and recurrent fetal loss. Cardiac involvement occurs frequently. Leaflet thickening and vegetations are detected quite often echocardiographically, but hemodynamically significant stenotic and/or regurgitant valvular disease is uncommon. Antiphospholipid syndrome can also cause left and right ventricular systolic and diastolic dysfunction as well as pulmonary hypertension. Other findings include spontaneous echo contrast and in situ mural thrombosis. In this review, the author discusses the major cardiac manifestations of antiphospholipid syndrome and highlights the role of echocardiography in their detection.

The geoepidemiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) can be detected by functional (lupus anticoagulant) and/or by solid phase assays (anti-cardiolipin and anti-beta2 glycoprotein I). Although detectable in 1-5% of asymptomatic apparently healthy subjects, persistent aPL are significantly associated with recurrent arterial/venous thrombosis and with pregnancy morbidity. Such an association is the formal classification tool for the antiphospholipid syndrome (APS). The prevalence of the syndrome with no associated systemic connective tissue diseases (primary APS) in the general population is still a matter of debate since there are no sound epidemiological studies in the literature so far. aPL display higher prevalence in systemic lupus erythematosus and rheumatoid arthritis than in other systemic autoimmune diseases. However not all the aPL positive lupus patients display the clinical manifestations. Comparable findings may be found in the paediatric population, although anti-beta2 glycoprotein I antibodies are detected in healthy children more frequently than in adults. High prevalence of aPL has been also reported in clinical manifestations that are not formal APS classification criteria: heart valve disease, livedo reticular, nephropathy, neurological manifestations, and thrombocytopenia. Antiphospholipid antibodies can be associated with infectious processes, active vaccination, drug administration and malignancies. Their prevalence and titres are lower and the relationship with the APS clinical manifestations are less strong than in the previously mentioned conditions. Ethnicity was also reported to influence the prevalence of aPL.

Antibody specificities associated with neutralization breadth in plasma from human immunodeficiency virus type 1 subtype C-infected blood donors

Defining the specificities of the anti-human immunodeficiency virus type 1 (HIV-1) envelope antibodies able to mediate broad heterologous neutralization will assist in identifying targets for an HIV-1 vaccine. We screened 70 plasmas from chronically HIV-1-infected individuals for neutralization breadth. Of these, 16 (23%) were found to neutralize 80% or more of the viruses tested. Anti-CD4 binding site (CD4bs) antibodies were found in almost all plasmas independent of their neutralization breadth, but they mainly mediated neutralization of the laboratory strain HxB2 with little effect on the primary virus, Du151. Adsorption with Du151 monomeric gp120 reduced neutralizing activity to some extent in most plasma samples when tested against the matched virus, although these antibodies did not always confer cross-neutralization. For one plasma, this activity was mapped to a site overlapping the CD4-induced (CD4i) epitope and CD4bs. Anti-membrane-proximal external region (MPER) (r = 0.69; P < 0.001) and anti-CD4i (r = 0.49; P < 0.001) antibody titers were found to be correlated with the neutralization breadth. These anti-MPER antibodies were not 4E10- or 2F5-like but spanned the 4E10 epitope. Furthermore, we found that anti-cardiolipin antibodies were correlated with the neutralization breadth (r = 0.67; P < 0.001) and anti-MPER antibodies (r = 0.6; P < 0.001). Our study suggests that more than one epitope on the envelope glycoprotein is involved in the cross-reactive neutralization elicited during natural HIV-1 infection, many of which are yet to be determined, and that polyreactive antibodies are possibly involved in this phenomenon.

Autoimmunity and HIV

PURPOSE OF REVIEW

This review focuses on some of the recent advances in the understanding of HIV immunopathogenesis and the diagnosis and treatment of several autoimmune conditions associated with HIV in the era of potent antiretroviral therapy.

RECENT FINDINGS

Chronic immune activation with progressive immune exhaustion are central features of HIV pathogenesis. The role of self-reactive T cells in the generation and maintenance of this process has recently been described. The understanding of the impact of immune dysregulation on the generation of autoimmune phenomena in HIV infection remains incomplete. The diagnosis of autoimmune diseases in the context of HIV is often difficult due to similarities in clinical presentations and laboratory markers. The antiretroviral therapy-associated immune reconstitution syndrome can present as autoimmune disease.

SUMMARY

The cause, frequency and prognosis of autoimmune conditions associated with HIV infection remain somewhat uncertain. Their management is often empirical with the use of novel immunosuppressive medication.

Infections and the antiphospholipid syndrome

Currently, the origin of autoimmune diseases is considered to be multifactorial. Genetic predisposition, immune system malfunction or even backfire, hormonal regulation, and environmental factors, i.e. infections, all play important roles in the pathogenesis of autoimmune diseases such as the antiphospholipid syndrome (APS). New drugs and strategies aimed at preventing infections could further improve the outcome of APS and other autoimmune diseases.

Prevalence of hepatitis C serum antibody in autoimmune diseases

OBJECTIVE

To evaluate the prevalence of serum antibodies against hepatitis C virus and other infectious agents in a large cohort of well-characterized patients with autoimmune diseases (AID).

METHODS

We utilized 1322 sera from patients with 18 different AID and 236 sera from healthy controls from the same countries and with similar age and sex distribution. All sera were tested for the presence of serum anti-hepatitis C virus (HCV) antibodies as well as antibodies directed at other infectious agents and autoantibodies.

RESULTS

Anti-HCV antibody was detected in 115/1322 (8.7%) of patients with AID and 0.4% of matched healthy controls (P < 0.0001). The prevalence of anti-HCV antibody was significantly higher in 7/18 different AID (i.e. cryoglobulinemia, mixed cryoglobulinemia pemphigus vulgaris, vasculitis, secondary anti-phospholipid syndrome, Hashimoto's thyroiditis, and inflammatory bowel disease) compared to controls. Patients with AID and serum anti-HCV positivity had an increased prevalence of antibodies against hepatitis B virus, Toxoplasma gondii and Cytomegalovirus as opposed to a lower frequency of serum autoantibodies.

CONCLUSIONS

The enhanced prevalence of anti-HCV serum antibodies in AID may suggest a role for HCV in tolerance to breakdown, similarly to its established role in mixed cryoglobulinemia. This immune mediated effect does not rule out the role of other infectious agents.

Laboratory tests in the diagnosis and follow-up of pediatric rheumatic diseases: an update

OBJECTIVES

We reviewed the literature to evaluate the role of common laboratory tests and to examine the recent progress in the laboratory diagnosis of pediatric rheumatic diseases.

METHODS

We used the PubMed database (1950-2008) to search for the keywords "laboratory," "erythrocyte sedimentation rate" (ESR), "C-reactive protein" (CRP), "blood cytology," "procalcitonin" (PCT), "complement system," "ferritin," "antistreptolysin O titer" (ASO), "autoantibodies," "genetic studies," in conjunction with "rheumatic disease in children" and "pediatric autoimmune diseases." All relevant original and review articles in English were reviewed as well as textbooks of pediatric rheumatology.

RESULTS

Laboratory tests (ESR, CRP, blood cytology, complement system, ferritin, ASO titer) play an important role in confirming a diagnosis and in the follow-up of rheumatic diseases in the pediatric age group. The ESR is probably the most widely measured index of the acute phase response. Measurement of CRP is very useful in the rapid diagnosis of infection as a progressive increase can be shown in the first 48 hours. Also, the subsequent fall in serum CRP concentration on resolution of inflammation is useful for monitoring the efficacy of treatment. In chronic diseases, a combination of CRP and ESR may provide the most useful information. Cytopenia and different forms of anemia can be encountered in many rheumatic diseases: they can be related to disease activity or to therapeutic side effects. Determination of complement levels (C3 and/or C4) is useful in the follow-up of systemic lupus erythematosus (SLE) and membranoproliferative glomerulonephritis. Ferritin is a laboratory hallmark of primary and secondary hemophagocytic lymphohistiocytosis. ASO titer should be obtained to confirm a diagnosis of acute rheumatic fever; other important antibody markers of streptococcal infection include antihyaluronidase, antideoxyribonuclease B, and antistreptokinase antibodies. We also found that, in the pediatric age, the main indication for synovial fluid analysis is suspected joint infection. Antinuclear antibodies, anti-Smith antigen, and anti-double-stranded DNA antibodies are important in the diagnosis of SLE, are useful prognostic markers, and facilitate clinical and treatment follow-up. Anti-SSA/Ro and anti-SSB/La antibodies are associated with Sjögren's syndrome and congenital heart block, while the anti-U1 small nuclear ribonucleoprotein antibodies show high specificity for mixed connective tissue disease. Repetitive spontaneous abortions, thrombocytopenia, and many types of venous or arterial thrombosis are associated with antiphospholipid antibodies. The presence of cytoplasmic antineutrophil antibodies is essential in the diagnosis of Wegener granulomatosis. The discovery of underlying single causative gene defects led to the identification of several autoinflammatory diseases, a group of genetic disorders characterized by recurrent attacks of inflammation (hereditary periodic fever syndromes). These include familial Mediterranean fever due to mutations in the Mediterranean fever (MEFV) gene, hyperimmunoglobulinemia D syndrome due to mutations in the MK gene for mevalonate kinase, cryopyrinopathies such as Muckle-Wells syndrome or neonatal-onset multisystemic inflammatory disease (neonatal-onset multisystemic inflammatory disease or chronic infantile neurological cutaneous and articular (CINCA)) associated with cold-induced autoinflammatory syndrome 1 gene mutations, and tumor necrosis factor receptor-associated periodic syndrome due to mutation of TNF receptor I gene.

CONCLUSIONS

Laboratory investigations play an important role in the diagnosis and follow-up of inflammatory rheumatic diseases in children. A good history and a complete physical examination are the best screening tests. Routine laboratory tests are useful to confirm a suspected diagnosis, to assess disease activity, and to measure the response and toxicity to treatment. Only a few tests represent diagnostic criteria such as antinuclear antibodies and anti-double-stranded DNA in SLE or cytoplasmic antineutrophil cytoplasmic autoantibodies in Wegener's granulomatosis. Recent advances in molecular genetics have impacted diagnosis, pathogenesis, and treatment in genetic fever syndromes.

Portal vein thrombosis in a patient with hepatitis C virus-related cirrhosis complicated with antiphospholipid syndrome

We report a rare case of portal vein thrombosis (PVT) associated with antiphospholipid syndrome (APS) and hepatitis C virus-related cirrhosis. A 59-year-old woman with hepatitis C virus (HCV) infection was admitted because of coma. The blood test showed a typically cirrhosis pattern including an elevated serum ammonia level. Abdominal computed tomography showed liver cirrhosis and thrombus in the right branch of the portal vein. To elucidate the cause of PVT, antiphospholipid antibodies were examined. Both IgG anti-cardiolipin antibody (ELISA) and IgG anti-cardiolipin-beta2 -glycoprotein I complex antibody (ELISA) were positive. When PVT is detected in a patient with cirrhosis, it might be necessary to examine antiphospholipid antibodies to clarify the cause of PVT.

The physiopathology of the catastrophic antiphospholipid (Asherson's) syndrome: compelling evidence

Catastrophic antiphospholipid (Asherson's) syndrome (cAPS) was described in the past as a severe variant of the antiphospholipid syndrome (APS). Currently growing evidence suggests it is a unique condition. This statement is based on several clinical and physiopathological features that although not well understood define cAPS by itself. The remarkable features of cAPS are the presence of antiphospholipid antibodies (aPLAs) and microthromboses. Additional physiopathological features are the presence of anemia and thrombocytopenia, which are also often described in similar autoimmune conditions. A strong association with concomitant infection is thought to act as the main trigger of microthromboses in cAPS. Several theories have been proposed to explain these physiopathological features. Some of them suggest the possibility of molecular mimicry between components of infectious microorganisms and natural anticoagulants, which might be involved in the production of cross-reacting aPLAs in cAPS. Some genetic risk factors have also been suggested to be implicated in the onset of cAPS, however they have not been defined yet. Herein, we review the remarkable physiopathological features commonly described in cAPS hitherto. We concluded that although they are not completely understood, it is possible to differentiate them from similar conditions. Nevertheless further studies on these physiopathological mechanisms of the disease are needed.

The antiphospholipid syndrome and infections in a child with trisomy 21

The relationship between infections and antiphospholipid antibodies or antiphospholipid syndrome is an intriguing question. A two and a half year old child with trisomy 21, who suffered three severe episodes of thrombosis each taking place after an infection, is described here. As high titres of IgG anticardiolipin (ACL) antibodies was registered during the second and third episodes, the antiphospholipid syndrome was suspected. IgM as well as IgG and IgA ACL antibodies have been described at different titres in a wide variety of infections, although they are not usually associated with thrombosis. In this particular case the timing of events and their association with high IgG ACL antibody titres seemed to implicate infection in the pathogenesis of the antiphospholipid syndrome. It can be hypothesized that some infections not only "trigger" antiphospholipid antibody production, but--in genetically predisposed subjects--can induce the clinical manifestations of the antiphospholipid syndrome.