Pathophysiology of the catastrophic antiphospholipid syndrome (CAPS)

Catastrophic antiphospholipid syndrome in Mexico. Literature review

Catastrophic antiphospholipid syndrome (CAPS) is a rare entity, approximately 600 cases have been reported around the world, and the prevalence in Mexico is unknown.

OBJECTIVE

To determine the estimated prevalence of CAPS in Mexico.

MATERIAL AND METHODS

A literature search of isolated clinical cases or case series was conducted in diverse search engines, using the terms: "Catastrophic Antiphospholipid Syndrome" and "Mexico" in May 2022.

RESULTS

We found a series of retrospective cases in autopsies that included 12 cases, two reports that included 2 cases each, and reports of 11 isolated clinical cases; these publications were generated between 2003 and 2020. In total, we collected data on 27 cases of CAPS, of which 16 correspond to primary antiphospholipid syndrome, 10 are associated with systemic lupus erythematosus, and 1 case corresponds to systemic sclerosis. The estimated prevalence rate in the Mexican population in 2022 is 2 cases per 10,000,000 inhabitants. The estimated mortality was 68% in this case series.

CONCLUSION

Cases of catastrophic antiphospholipid syndrome in Mexico are underreported; identifying them will help improve current diagnostic and therapeutic strategies used in the country, encouraging the implementation of triple therapy and, in refractory cases, the use of eculizumab, to reduce current mortality.

A Rare Rheumatologic Case of Catastrophic Antiphospholipid Syndrome

A very rare and severe disease catastrophic antiphospholipid syndrome is defined by small vessel occlusions resulting in multi-organ involvement in the presence of antiphospholipid antibodies. This case report presents a case of catastrophic antiphospholipid syndrome in a young female without past medical history.

Acute dilated cardiomyopathy in the setting of catastrophic antiphospholipid syndrome and thrombotic microangiopathy: A case series and review

Catastrophic antiphospholipid antibody syndrome (CAPS) is a rare form of antiphospholipid syndrome, an autoimmune condition characterized by vascular thromboses, pregnancy loss, and antiphospholipid (aPL) antibodies. Diagnosis of CAPS relies on thrombosis of at least three different organs systems over 1 week, histopathological evidence of small vessel occlusion, and high aPL antibody titers. In a subset of precipitating circumstances, activation or disruption of endothelial cells in the microvasculature may occur along with cardiomyopathy. We present two cases of CAPS‐associated dilated cardiomyopathy at our institution, focusing on disease management, pathophysiology, and treatment. These patients were of Southeastern Asian descent, raising the possibility of genetic polymorphisms contributing to the development of cardiomyopathy. Both met CAPS criteria and both demonstrated clinicopathologic thrombotic microangiopathy (TMA) and complement activation and developed severe dilated cardiomyopathy with shock. Complement activation plays an important role in the development of CAPS and may be important in the pathogenesis of CAPS‐associated cardiomyopathy. Clinical suspicion for TMA as a pathophysiologic mechanism of unexplained heart failure in CAPS is important and increased awareness of cardiac side effects is necessary so that early treatment can be initiated to halt further cardiac and systemic complications.

Thrombocytopenia in Critical Care Patients

Thrombocytopenia is a common laboratory finding in the intensive care unit (ICU) patient. Because the causes can range from laboratory artifact to life-threatening processes such as thrombotic thrombocytopenic purpura (TTP), identifying the cause of thrombocytopenia is important. In the evaluation of the thrombocytopenia patient, one should incorporate all clinical clues such as why the patient is in the hospital, medications the patient is on, and other abnormal laboratory findings. One should ensure that the patient does not suffer from heparin-induced thrombocytopenia (HIT) or one of the thrombotic microangiopathies (TMs). HIT can present in any patient on heparin and requires specific testing and antithrombotic therapy. TMs cover a spectrum of disease ranging from TTP to pregnancy complications and can have a variety of presentations. Management of disseminated intravascular coagulation depends on the patient’s condition and complication. Other causes of ICU thrombocytopenia include sepsis, medication side effects, post-transfusion purpura, catastrophic anti phospholipid antibody disease, and immune thrombocytopenia.

Antibody profile in Indian severe haemophilia A patients with and without FVIII inhibitors

Diagnosis and management of haemophilia patients with inhibitors is often tricky due to the heterogeneous nature of the antibodies with regard to their kinetics, as well as the co-existence of other interfering antibodies. Plasma samples from severe haemophilia A patients from India with and without FVIII inhibitors were analysed for the presence of possible co-existing antibodies such as lupus anticoagulants (LA), anti-cardiolipin antibodies (ACLA), anti-β2-glycoprotein-I (anti-β2-GP-I) antibodies, viral transfusion transmitted disease (HIV, HBsAg, HCV) related antibodies, anti-cyclic citrullinated peptides (anti-CCP), and anti-nuclear antibodies. A high incidence of LA and anti-HCV antibodies was detected in Indian haemophilia A patients similar to earlier reports. More importantly, a relatively high incidence of autoantibodies to nuclear antigens (18.62%) and anti-CCP antibodies (1.38%) associated with autoimmune disorders was also seen in these congenital haemophilia A patients with and without inhibitors. Knowledge on the antibody profile in these haemophilia patients especially in those with FVIII inhibitors along with correlation with the clinical manifestations and other risk factors for inhibitor development could possibly shed more light on the complex immune response in these patients.

Guidelines on the use of therapeutic apheresis in clinical practice--evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (fourth edition), the subcommittee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Fifth ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by refining the category definitions and by adding a grade of recommendation based on widely accepted GRADE system. The concept of a fact sheet was introduced in the Fourth edition and is only slightly modified in this current edition. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. The article consists of 59 fact sheets devoted to each disease entity currently categorized by the ASFA as category I through III. Category IV indications are also listed.

Immune response to FVIII in hemophilia A: an overview of risk factors

Development of inhibitors is perhaps the most serious complication of factor VIII (FVIII) replacement therapy, which can practically preclude efficient clinical management of patients with hemophilia A. Much effort therefore has been focused both in improving our understanding of the reasons for the formation of FVIII antibodies and to find alternative methods of treatment. Several patient-related factors have been related to the risk of inhibitor development such as ethnicity, FVIII gene mutation type, family history of inhibitors, HLA haplotype, polymorphisms in the promoter regions of IL 10 gene, single nucleotide polymorphisms of tumor necrosis factor alpha gene, and so on. In addition to the genetic determinants, there are several nongenetic factors which mainly include treatment characteristics like the type and purity of coagulation factor concentrates used for treatment, age at the time of initial treatment, initial doses of concentrate, mode of infusion, surgery, frequency of dosing prior to inhibitor development, and intensity of treatment or regular prophylaxis. Inflammatory processes in early childhood are under discussion as being an environmental factor that may modify the immune response to a foreign antigen. The genetic risks cannot be changed, while environmental factors may increase or decrease the inhibitor risk in an individual patient. In addition, there are other causes of inhibitor development against FVIII like stress, age, malignancy, infection, pregnancy, antibiotics, etc. Development of inhibitors in such cases happens in individuals who are not hemophilic and have normal plasma FVIII levels. Acquired inhibitors to FVIII in nonhemophiliacs (autoantibodies) pose a further challenge to treatment, as this is often associated with significant morbidity and mortality. Prognosis in case of autoantibodies is related to the underlying disease process and is associated with high mortality. Improved understanding of these complex interactions may lead to the development of preventive measures to minimize FVIII inhibitor formation. The modifiable risk factors for inhibitor formation may provide the key to predict and perhaps prevent the formation of inhibitors in hemophilia patients.

Primary antiphospholipid syndrome with thrombotic thrombocytopenic purpura: a very unusual association

This report considers the rare situation in which primary antiphospholipid syndrome (PAPS) is linked with thrombotic thrombocytopenic purpura (TTP). It describes the case of a young lady with PAPS, characterized by recurring cerebro-vascular abnormalities and marked livedo reticularis, combined with circulating anticardiolipin and lupus anticoagulant antibodies. On follow-up, while on oral anticoagulation, she developed severe thrombocytopenia associated with hematuria, microangiophatic anaemia and neurological manifestations consistent with a diagnosis of TTP. The patient was treated with pulses of methylprednisolone and plasmapheresis with plasma exchange. The result was a favourable outcome. To our knowledge, this is the seventh report on this rare association in the English-language literature of this field.

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 role of malignancies in patients with catastrophic anti-phospholipid (Asherson’s) syndrome

The catastrophic anti-phospholipid syndrome (CAPS) differs from the anti-phospholipid syndrome in its accelerated systemic involvement leading to multi-organic failure. In this study, the occurrence of malignancies in patients with CAPS was evaluated and the clinical findings of CAPS patients with and without malignancies were compared. We investigated the web site-based international registry of patients with CAPS for all cases in which both CAPS and underlying malignancies were present. The clinical characteristics of these cases were subsequently evaluated to establish common characteristics. The CAPS registry included information on a total of 262 cases. Twenty-three (9%) patients suffered from malignancies. In 78% of these patients, the malignancy itself or the treatment modalities instituted for the carcinoma was the precipitating factor of CAPS. Only 39% of CAPS patients with malignancies recovered in comparison to 58% of patients without malignancies (p = 0.07). Treatment modalities, however, did not differ significantly between these patients. Infections were not evident as precipitating factors for any of the malignancy patients. The mean age of patients with malignancies was 9 years older than the average age of other patients with CAPS and the prevalence of SLE was significantly less common than in patients without malignancy. Malignancy may play a pathogenic role in patients with CAPS, whereas infections are more important as triggering factors in patients without malignancies. CAPS patients with malignancies are generally older than CAPS patients without malignancies; they generally have the worst prognosis of the entire CAPS cohort.

Guidelines on the use of therapeutic apheresis in clinical practice—Evidence-based approach from the apheresis applications committee of the American society for apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. This elaborate process had been undertaken every 7 years resulting in three prior publications in 1986, 1993, and 2000 of "The ASFA Special Issues." This article is the integral part of the Fourth ASFA Special Issue. The Fourth ASFA Special Issue is significantly modified in comparison to the previous editions. A new concept of a fact sheet has been introduced. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. A detailed description of the fact sheet is provided. The article consists of 53 fact sheets devoted to each disease entity currently categorized by the ASFA. Categories I, II, and III are defined as previously in the Third Special Issue. However, a few new therapeutic apheresis modalities, not yet approved in the United States or are currently in clinical trials, have been assigned category P (pending) by the ASFA Clinical Categories Subcommittee. The diseases assigned to category IV are discussed in a separate article in this issue.

Catastrophic antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a thrombotic disorder associated with autoantibodies that target membrane phospholipids and phospholipid-binding proteins, which regulate coagulation. APS is usually characterized by major arterial or venous occlusions, pregnancy complications, or both. In 1992, Asherson described an unusual variant of APS termed the catastrophic antiphospholipid syndrome (also known as Asherson's syndrome), the hallmark of which is rapid multiorgan failure caused by widespread small-vessel thrombi. Empiric treatments have improved the prognosis of patients, but half still die from thrombotic diathesis, even though those who survive the acute stages frequently remain well. Given the persistently high mortality rate, efforts have been underway to facilitate early diagnosis, institute effective treatments in a timely manner and to better understand the cause (or causes) of this extreme condition in order to improve outcomes.

Catastrophic antiphospholipid syndrome and pulmonary embolism in a 3-year-old child

We report a rare example of catastrophic antiphospholipid syndrome (CAPS) in a young child. A 3-year-old girl with no previous medical history presented with extensive and recurrent thromboses. The diagnosis of CAPS was based on the occurrence of cardiopulmonary embolism in the child with a high titre of autoantibodies directed against phospholipids and beta-2-glycoprotein 1. In spite of a relatively rapid diagnosis and multiple treatments, the outcome was unfavourable. Multimodality imaging, including both ultrasonography and spiral CT, allowed close follow-up of the thromboses.

Catastrophic antiphospholipid syndrome in a 14-year-old child

Antiphospholipid syndrome (APS) is an autoimmune disease. Less than 1% of patients with APS present with life-threatening catastrophic APS (CAPS). We report here a case of CAPS in a young girl with cardiac, gastrointestinal and renal involvement. Although the management was complicated, the outcome was better than expected. We suggest that CAPS be included in the differential diagnosis of acute renal failure in children with multi-organ involvement and prolonged phospholipid-dependent coagulation time and promptly treated with immunomodulating agents and anticoagulants.

Prevention of thrombosis with prostaglandin E1 in a patient with catastrophic antiphospholipid syndrome

PURPOSE

Catastrophic antiphospholipid syndrome (CAPS) is a variant of antiphospholipid syndrome and presents with life-threatening symptoms of multiorgan failure due to thrombosis. We present a patient with CAPS secondary to an ovarian cancer. In such cases, it is believed that the thrombotic risk disappears after surgical removal of the cancer. The intraoperative management was challenging because of the risks of two opposing complications: catastrophic exacerbation of the thrombotic tendency triggered by the surgical stimulus and major bleeding due to the necessary anticoagulation. We describe the intraoperative management of hemostasis in a patient with CAPS.

CLINICAL FEATURES

A 44-yr-old female patient with CAPS underwent resection of an ovarian cancer, which was suspected to be associated with her coagulation abnormality. She had both arterial and venous thromboembolism, including cerebral infarction, embolic gangrene, and pulmonary emboli. Serological examinations revealed increased anticardiolipin IgG antibody and decreased protein C activity. Before surgery, an inferior vena cava filter was placed to prevent perioperative pulmonary embolism. Prostaglandin E(1) (PGE(1); 100 ng.kg(-1).min(-1)) was given intraoperatively to suppress platelet aggregation and thrombin generation and to maintain arterial blood flow. No apparent coagulation abnormalities were observed during surgery, neither hypercoagulation nor a tendency to bleed. No additional thrombotic symptoms developed during a six-month follow-up.

CONCLUSION

The use of PGE(1), an inhibitor of thrombin formation and platelet function, and placement of an inferior vena cava filter were associated with the uneventful surgical resection of an ovarian cancer in a patient with CAPS.

Childhood acute myelomonocytic leukemia (AML-M4) presenting as catastrophic antiphospholipid antibody syndrome

: The authors describe a 15-year-old girl presenting with a cerebral ischemic stroke as the first manifestation of catastrophic antiphospholipid antibody syndrome secondary to acute myeloid leukemia (AML). Despite treatment with anticoagulants, therapeutic plasma exchange, and chemotherapy, the patient developed multiorgan thromboses and failure, eventually culminating in death. This unusual presentation of AML has not been previously described in children. Clinical features of antiphospholipid antibody syndrome and current knowledge regarding its association with malignancies are reviewed.

Recurrent life-threatening thromboembolism and catastrophic antiphospholipid syndrome in a patient despite sufficient oral anticoagulation

We report on a 32-year old female patient with primary antiphospholipid syndrome (PAPS) and several thromboembolic events despite stable doses of oral anticoagulation, good patient compliance and maintained INR values of >3. Over the preceding 3 years the patient had presented a wide spectrum of manifestations of APS, including recurrent venous and arterial thromboses, cardiac, gynecological (HELLP syndrome), neurological involvements, livedo reticularis, a mild thrombocytopenia and the most feared manifestation of the catastrophic antiphospholipid syndrome (CAPS). Life-threatening bilateral subdural bleeding occurred while she was anticoagulated. The clinical features appeared to be refractory to oral anticoagulation with phenprocoumon. They were life threatening on each occasion and she developed repetitive episodes of organ damage with cardiac insufficiency (NYHA III), pulmonary hypertension and other residual defects. Even during heparinization recurrent thromboembolism supervened as well as livedo reticularis of the extremities. Lupus anticoagulants (LAC), anticardiolipin (aCL) antibodies and anti-β₂-glycoprotein-1 (β₂GPI) titers were all markedly elevated. This case report shows that recurrent episodes of thrombosis can occur despite seemingly adequate anticoagulation in patients with CAPS.

Antiphospholipid syndrome: a survey of clinical characters in ten cases

OBJECTIVE

To gain further understanding of the antiphospholipid syndrome(APS).

METHODS

Analysing clinical and laboratory data on ten cases of APS.

RESULTS

Thrombocytopenia appeared in all cases. Venous thrombi of limbs appeared in five cases and neurological abnormalities in two cases. Renal impairments were found in three cases. One case manifested left renal venous thrombi and the other two cases thrombotic microangiopathy. Budd-Chiari syndrome was found in one case. One of the ten cases was catastrophic APS (CAPS) presented as acute diffuse swelling, cyanosis, pain, ischemia and necrosis in fingers and limbs, recurrent shock, ascites, hepatic and respiratory dysfunction. Anticoagulants and corticosteroids could be effective for dealing with APS. It was critical to treat catastrophic APS with anticoagulants or plasmapheresis as early as possible.

CONCLUSIONS

APS shows variable manifestations for good prognosis, but catastrophic APS has fatal risk. The main treatment for APS is the use of anticoagulants and immunosuppressives.

Catastrophic antiphospholipid syndrome masquerading as ischaemic colitis

We describe a young woman whose initial presentation was dominated by acute diarrhoea. Life-threatening multiorgan failure rapidly ensued and necessitated mechanical ventilation and dialysis treatment. An initially elongated activated partial thromboplastin time prompted further coagulation tests that led to the detection of positive lupus anticoagulant, a highly elevated IgG-anticardiolipin (aCL) antibody titre, and prolonged dilute Russell's viper venom time. Histological examination of samples obtained during endoscopy revealed widespread intestinal thrombotic microangiopathy. In view of these serologic and histologic features, a diagnosis of the malignant variant of the antiphospholipid syndrome (APS), also termed 'catastrophic APS', was established. In spite of this syndrome's grim prognosis, the patient recovered following intensive anticoagulation and adjunct treatment with steroids and immunoglobulins.

Combined plasmapheresis and immunosuppression as rescue treatment of a patient with catastrophic antiphospholipid syndrome occurring despite anticoagulation: a case report

We report the case of a 33-year-old female with known primary antiphospholipid syndrome who, despite full-dose oral anticoagulation, presented with myocardial infarction, acute respiratory distress syndrome, purulent bronchitis, and septic shock. Antiphospholipid antibodies and anti-beta2-glycoprotein-1 titres were markedly elevated. The patient was diagnosed with catastrophic antiphospholipid syndrome and treated with unfractionated intravenous heparin. However, she developed thromboembolism of the right foot and skin marmoration of her extremities during heparin therapy, and therefore plasmapheresis, immunoglobulins, cyclophosphamide, and methylprednisone under a broad spectrum of anti-infective therapy were instituted. This treatment led to a rapid decrease of antiphospholipid antibody and anti-beta2-glycoprotein-1 titres, and the patient's condition gradually improved. Upon discharge from the hospital, pulmonary infiltrates had markedly regressed, and she was feeling well. Given the high mortality of catastrophic antiphospholipid syndrome, this report emphasizes the need for rapid diagnosis and effective multimodal treatment in an intensive care unit setting for these patients.

Antiphospholipid antibodies

OBJECTIVE

To review the role of lupus anticoagulants in the pathogenesis of both venous and arterial thromboembolic events, as well as in recurrent spontaneous abortions. The pathophysiology of lupus anticoagulants and associated antiphospholipid antibodies (eg, anticardiolipin antibodies) is also discussed.

DATA SOURCES

Review of the recent medical literature.

DATA EXTRACTION AND SYNTHESIS

Key articles in the recent medical literature dealing with lupus anticoagulants and their role in pathogenesis of thromboembolic events were reviewed. Plasma proteins that have an affinity for binding to "perturbed cellular membranes" have been identified as the antigenic targets for antiphospholipid antibodies. Thus, the concept of antiphospholipid antibodies needs to be reevaluated. Perhaps a better term is antiprotein-phospholipid antibodies. The principal antigenic protein targets are beta(2)-glycoprotein I, prothrombin, and a wide range of additional proteins that interact with activated cellular membranes, including protein C, protein S, annexin V, etc. Most research reported in the literature has focused on beta(2)-glycoprotein I and human prothrombin.

Catastrophic antiphospholipid syndrome in the intensive care unit

CAPS is characterized by development of widespread microvascular thrombosis. Patients at risk are those with positive aCL or LA factor. Precipitating events, such as infection, trauma, surgical procedures, or reduction in anticoagulation therapy, may contribute to the development of CAPS. Presentation to the ICU can be dramatic, with progressive multiorgan failure and need for rapid institution of life-supporting measures. Cardiopulmonary failure has been the major contributor to mortality. A variety of therapeutic modalities have been used in an attempt to offset the widespread thrombosis and organ damage from high aCL levels. Anticoagulation therapy and high dosages of steroids seem to have a positive effect on survival.

"Black swan in the kidney": renal involvement in the antiphospholipid antibody syndrome

The antiphosphospholipid antibody syndrome (APS) describes a clinical entity with recurrent thrombosis, fetal loss, thrombocytopenia in the presence of lupus anticoagulant and/or antibodies to cardiolipin. These antibodies may be associated with connective tissue diseases such as systemic lupus erythematosus (secondary APS) or be found in isolation (primary APS). Renal syndromes increasingly being reported in association with these antibodies include thrombotic microangiopathy, renal vein thrombosis, renal infarction, renal artery stenosis and/or malignant hypertension, increased allograft vascular thrombosis, and reduced survival of renal allografts. Although much has been understood concerning the biology of these antibodies and the pathogenesis of thrombosis, the optimal therapy remains to be elucidated. This article presents a historical review of the renal involvement in the antiphospholipid syndrome and discusses therapeutic options. Further research is needed.

Catastrophic antiphospholipid syndrome in a patient with Behçet's disease

We report on a patient who had a life-threatening relapse of Behçet's disease associated with a catastrophic antiphospholipid syndrome. The patient experienced over a short time a recurrent acute myocardial infarction, multiple venous thromboses, uveitis, and erythema nodosum. Search for thrombophilic factors was positive only for lupus anticoagulant (LAC) and criteria for the diagnosis of the antiphospholipid antibody syndrome were fulfilled. LAC was not found three months after the discharge. At that time the patient had no evidence of clinically active disease or thrombosis. We suggest that LAC was the main triggering factor for the repeated thromboses in this patient.

Annexins: from structure to function

Annexins are Ca2+ and phospholipid binding proteins forming an evolutionary conserved multigene family with members of the family being expressed throughout animal and plant kingdoms. Structurally, annexins are characterized by a highly alpha-helical and tightly packed protein core domain considered to represent a Ca2+-regulated membrane binding module. Many of the annexin cores have been crystallized, and their molecular structures reveal interesting features that include the architecture of the annexin-type Ca2+ binding sites and a central hydrophilic pore proposed to function as a Ca2+ channel. In addition to the conserved core, all annexins contain a second principal domain. This domain, which NH2-terminally precedes the core, is unique for a given member of the family and most likely specifies individual annexin properties in vivo. Cellular and animal knock-out models as well as dominant-negative mutants have recently been established for a number of annexins, and the effects of such manipulations are strikingly different for different members of the family. At least for some annexins, it appears that they participate in the regulation of membrane organization and membrane traffic and the regulation of ion (Ca2+) currents across membranes or Ca2+ concentrations within cells. Although annexins lack signal sequences for secretion, some members of the family have also been identified extracellularly where they can act as receptors for serum proteases on the endothelium as well as inhibitors of neutrophil migration and blood coagulation. Finally, deregulations in annexin expression and activity have been correlated with human diseases, e.g., in acute promyelocytic leukemia and the antiphospholipid antibody syndrome, and the term annexinopathies has been coined.

Autoantibodies Associated with Rheumatic Diseases

The identification of circulating autoantibodies contributes to the correct diagnosis as well as to the follow-up of rheumatic diseases. Some autoantibodies are even included in diagnostic and classification criteria for these types of autoimmune diseases. There are several relatively specific screening and identification methods for the measurement of autoantibodies available. The type of assay crucially influences the diagnostic value of the parameters. In general, routine laboratories should prefer enzyme immunoassays (ELISA) using well characterized antigens, although ELISA tests tend to produce more false-positive and true weakly positive results, which reduce their positive predictive value. Therefore one should be aware that laboratory results can only be properly interpreted when there is a correlation with the clinical situation and when the limitations of the technologies used for autoantibody identification have been taken into consideration. A diagnostic algorithm consisting of screening and identification steps should be established by each laboratory in order to create a rational, evidence-based and cost-effective basis for the diagnosis of rheumatic diseases.