Acquired Circulating Anticoagulants

The Antiphospholipid Thrombosis Syndromes: A Common Multidisciplinary Medical Problem

Antiphospholipid antibodies are increasingly being identified as a cause of arterial and venous thrombosis as well as fetal wastage syndrome via placental vascular thrombosis. The antiphospholipid thrombosis syndromes should be considered and searched for when suggestive clinical findings are present or when unexplained arterial or venous thrombosis occurs. Noting the presence and type of antiphospholipid antibody thrombosis syndrome assumes major importance with respect to not only making an accurate diagnosis of cause of thrombosis but also in selecting effective antithrombotic therapy. The antiphospholipid thrombosis syndromes and the thrombotic and other clinical manifestations span almost all medical specialities and should be construed as a truly multidisciptinary medical problem. Key Words: Thrombosis-Anticardiolipin antibody—Lupus anticoagulant.

The relationship between the antiphospholipid syndrome and heparin-induced thrombocytopenia

Antiphospholipid syndrome (APS) and heparin-induced thrombocytopenia (HIT) are immune-mediated thrombotic conditions caused by antibodies targeted to a protein-antigen complex. Although each disorder is attributed to two distinct antibodies, these autoimmune disorders are characterized by a similar pathogenesis that includes a hypercoagulable state, platelet activation, damage to the vascular endothelium, and inflammation. APS and HIT share similarities in the clinical presentation because each is associated with thrombocytopenia, a high risk of thrombosis in all venous and arterial sites, and catastrophic thrombotic outcomes occur if untreated. Understanding the disease process for one disorder could potentially aid in understanding the other disorder.

The antiphospholipid syndrome

Antiphospholipid syndrome is an autoimmune disorder characterized by the association between antiphospholipid antibodies and venous or arterial thrombosis or obstetric complications. In spite of the recent progresses, many aspects of this disease remain unclear. In this review, we briefly focus on the most important advances in the pathophysiology, diagnosis and treatment of this condition.

Antiphospholipid thrombosis syndromes

Antiphospholipid antibodies are associated strongly with thrombosis and are the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanisms whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, numerous theories, as previously discussed, have been advanced. The most common thrombotic events associated with ACLAs are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). Patients with type V disease are those with antiphospholipid antibodies and RMS. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of ACLAs in association with arterial and venous thrombosis strongly suggests that they should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I-VI) should be defined, if possible, because this identification may dictate both the type and the duration of immediate and long-term anticoagulant therapy. Unlike those patients with ACLAs, patients with primary LA-thrombosis syndrome usually have venous thrombosis. Because the aPTT is unreliable in patients with LA (prolonged in only approximately 40%-50% of patients) and usually is not prolonged in patients with ACLAs, definitive tests, including ELISA for ACLA, the dilute Russell's viper venom time for LA, hexagonal phospholipid-neutralization procedure, and B-2-GP-I (IgG, IgA, and IgM) should be ordered immediately when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If these test results are negative, subgroups also should be assessedin the appropriate clinical setting. Most patients with antiphospholipid thrombosis syndrome will fail to respond to warfarin therapy, and except for retinal vascular thrombosis, may fail some types of antiplatelet therapy, so it is of major importance to make this diagnosis so patients can be treated with the most effective therapy for secondary prevention-LMWH or unfractionated heparin in most instances and clopidogrel in some instances.

Antiphospholipid thrombosis syndromes

Antiphospholipid antibodies are strongly associated with thrombosis and are the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagutable state remain unclear, numerous theories, as previously discussed, have been advanced. The most common thrombotic events associated with anticardiolipin antibodies are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type II syndrome); occasionally, patients present with mixtures of these types (type IV syndrome). Type V patients are those with antiphospholipid antibodies and RMS. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of anticardiolipin antibodies in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through VI) should be defined if possible, as this may dictate both type and duration of both immediate and long-term anticoagulant therapy. Unlike those with anticardiolipin antibodies, patients with primary lupus anticoagulant thrombosis syndrome usually experience venous thrombosis. Because the aPTT is unreliable inpatients with lupus anticoagulant (prolonged in only about 40 to 50% of patients) and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests, including ELISA for anticardiolipin antibodies, the dRVVT for lupus anticoagulant, hexagonal phospholipid neutralization procedure, and beta-2-GP-I (IgG, IgA, and IgM) should be immediately ordered when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If results of these tests are negative, in the appropriate clinical setting, subgroups should also be assessed. Finally, most patients with antiphospholipid thrombosis syndrome will fail warfarin therapy and, except for retinal vascular thrombosis, may fail some types of antiplatelet therapy; thus it is of major importance to make this diagnosis so that patients can be treated with the most effective therapy for secondary prevention--LMWH or UH in most instances, and clopidogrel in some instances.

Vascular thrombohemorrhagic disorders: hereditary and acquired

This review has summarized the more important diseases that may be accompanied by or lead to a disorder of hemostasis or thrombosis via alterations of the vasculature. It is to be stressed that the vascular component of hemostasis is often overlooked by clinicians caring for patients with disorders of hemostasis and thrombosis. It should be appreciated that the vasculature is intricately related to the coagulation protein system and to platelets when involved in thrombohemorrhagic diatheses. Although many vascular disorders may lead to hemorrhage or thrombosis, it must be appreciated that often it is impossible to discern between a primary vascular defect/damage and a defect that has been induced by platelet activation/dysfunction or procoagulant abnormalities.

Inhibitors against factor VIII in patients with cancer. Analysis of 41 patients

BACKGROUND

The spontaneous formation of neutralizing antibodies (inhibitors) to factor VIII (FVIII) in patients with cancer is a well known phenomenon. However, to the authors' knowledge there is lack of information in the literature with respect to the clinical course of these patients and the nature of the association between malignant tumors and acquired hemophilia.

METHODS

A retrospective study of 41 patients with cancer and acquired hemophilia was conducted. The patients were identified through a MEDLINE search between 1974-2000. All patients had detailed clinical and laboratory information available and descriptions of the course of the inhibitor in relation to cancer treatment. The patients were divided into two groups: responders and nonresponders. The stage of the tumor, inhibitor titer, FVIII level, and survival data were examined and compared between the two groups.

RESULTS

A total of 63 hemorrhagic episodes were reported in 25 patients with solid tumors and 16 patients with hematologic malignancies. The median inhibitor titer at the time of the diagnosis of acquired hemophilia was 14 Bethesda units (BU) (range, 1-435 BU). The complete response (CR) rate to treatment of the inhibitor was 70% and patients who achieved a CR were more likely to have early stage tumors (P = 0.0007) and a lower median inhibitor titer at the time of presentation compared with nonresponders (12 BU vs. 78 BU; P = 0.007). The overall survival was significantly higher in patients who achieved a CR compared with patients with a persistent inhibitor (75% vs. 17%; P = 0.0006).

CONCLUSIONS

Although it remains an uncommon occurrence, the development of inhibitors to FVIII should be considered as a cause of bleeding in some patients with malignant diseases. Because of the high response rate and the impact of this type of hemorrhage on cancer patients, efforts should be directed toward immunosuppression of the inhibitor in a fashion similar to that used in other patients with acquired hemophilia. To our knowledge the link between malignancy and the formation of antibodies to FVIII is unclear; however, it appears that treatment of cancer with chemotherapy or surgery may accelerate the eradication of the inhibitor in some patients. Long term prospective studies are needed to better assess the association between cancer and acquired hemophilia.

Serum cardiolipin antibodies in cancer patients with thromboembolic events

This study was undertaken to investigate a possible association of anticardiolipin antibodies (ACLAs) in cancer patients with thromboembolic events. Twenty-five patients with solid tumors complicated with acute thrombosis, 36 cancer patients without any thrombotic events, and a group of 20 healthy volunteers without thrombosis or malignancy were included. The mean age of the cancer patients with and without thrombosis and healthy subjects were 50 years (range 20-75), 45 years (range 23-66), and 40 years (range 20-68), respectively. Deep venous thrombosis (n = 16) and thrombosis of the central venous port-catheter systems (n = 9) were confirmed by Doppler sonography in all patients. IgG and IgM isotypes of ACLAs were quantitated by enzyme-linked immunosorbent assay with normal levels of < 23 GPL and < 11 MPL, respectively. Mean values of IgG ACLAs were found similar in cancer patients with acute thrombosis (13.8 +/- 4.9 GPL), without thrombosis (12.8 +/- 5.4 GPL) or in healthy subjects (14.8 +/- 5.5 GPL). Although the mean values of IgM ACLAs were within normal limits in all groups, cancer patients with thrombotic events had higher levels of IgM ACLAs (mean = 10.5 +/- 2.2 MPL) than cancer patients without thrombosis (mean = 4.6 +/- 2.4 MPL) (p = .01). Healthy subjects also had lower levels of IgM ACLAs (mean = 7.1 +/- 3.2 MPL) than cancer patients with thrombosis (p = .16). In addition, a higher percentage of cancer patients with or without thrombosis had IgM and IgG ACLA levels above normal limits compared with healthy controls. In conclusion, our study suggests an association between ACLAs or IgG and particularly IgM isotypes and venous thrombosis in malignancy. Identification of cancer patients who are at higher risk for developing thromboembolic events might lead to a better selection of patients for prophylactic anticoagulant therapy.

Thrombosis and hemorrhage in oncology patients

As outlined in this review, patients with cancer may harbor many alterations of hemostasis. These are multifaceted and must be considered when trying to control hemorrhage or thrombosis in cancer patients. Also, hemorrhage or thrombosis is often the final fatal event in many patients with metastatic solid tumor or hematologic malignancies. Patients with malignancy present a major clinical challenge in this new era of oncologic awareness and more aggressive care, which has led to prolonged survival for patients and a longer time frame during which these complications may develop. Therefore, these complications are occurring more commonly. It is important to realize that these alterations of hemostasis exist and must be approached in a sequential and logical manner with respect to diagnosis; only in this way can responsible, efficacious, and rational therapy be delivered to patients. By far the most common alteration of hemostasis in malignancy is that of hemorrhage associated with thrombocytopenia, either drug-induced, or radiation-induced, or from bone marrow invasion. Hemorrhage resulting from DIC, however, is also quite common and may present as hemorrhage, thrombosis, thromboembolus, or any combination thereof. Many antineoplastic drugs and radiation therapy may lead to or significantly enhance hemorrhage in patients with malignancy. Thrombosis, also commonly seen in patients with malignancy, is often a manifestation of low-grade DIC. When approaching the patient with malignancy and either hemorrhage or thrombosis, all the potential defects in hemostasis must be considered, defined from the laboratory standpoint, and treated in as precise and logical manner as possible.

Alteration of the aPA ELISA by UV exposure of polystyrene microtiter plates

Interlaboratory inconsistencies in antiphospholipid antibody (aPA) solid phase assays have prompted controversy in clinical laboratory testing for aPA. We found that the aPA ELISA can be influenced by the type of microtiter plate utilized and by the conditions in which the plates are stored. By exposing 96-well, flat-bottom polystyrene microtiter plates to short wave UV light (254 nm), the aPA ELISA signal decreased in a UV dose-dependent manner. No effect was seen with long wave UV light (366 nm). These results were independent of the antibody isotype under study or the phospholipid (PL) antigen used: anionic phosphatidylserine (PS) and cardiolipin (CL), or zwitterionic phosphatidylethanolamine (PE). Purified human beta 2-glycoprotein I (beta 2 GPI), a known cofactor for anionic PL, and rabbit anti-beta 2 GPI antisera were used to demonstrate that beta 2 GPI bound equally to UV treated and untreated microtiter plates. In contrast, recognition of beta 2 GPI on an anionic PL surface was decreased on UV treated plates, suggesting that UV exposure alters the lipid binding properties of the microliter plate. To determine whether UV exposure inhibited PL binding directly or caused a change in the way the PL was bound, the amount of PL bound to UV treated and untreated plates was measured by using fluorescent labeled PS and a fluorimeter. PS binding was decreased by 53% in UV treated wells as compared to untreated wells. These data show that short wave UV exposure reduces PL binding to polystyrene microtiter plates, thereby reducing the amount of beta 2 GPI bound to PL coated ELISA plates. Thus by using UV exposed microtiter plates, decreased or false-negative a PA ELISA results may be obtained for aPA positive plasmas.

The antiphospholipid and thrombosis syndromes

Anticardiolipin antibodies and the lupus anticoagulant are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories have been advanced. The commonest thrombotic events associated with anticardiolipin antibodies are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). The relative frequency of anticardiolipin antibodies in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through IV) should be defined if possible because this may dictate both type and duration of immediate and long-term anticoagulant therapy. In contrast to those with anticardiolipin antibodies, patients with primary lupus anticoagulant thrombosis syndrome usually suffer venous thrombosis. Because the aPTT is unreliable in patients with lupus anticoagulant (prolonged in only about 40% to 50% of patients) and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests (ELISA for anticardiolipin antibody and the dRVVT for lupus anticoagulant) should be immediately ordered when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events.

Acquired factor VIII inhibitor preceding chronic lymphocytic leukemia

An acquired factor VIII inhibitor was found in an 82-year-old woman who presented with numerous spontaneously appearing ecchymoses. Coagulation studies revealed the presence of a prolonged activated partial thromboplastin time that was not corrected by 1:1 mixture with normal fresh plasma after a 2-h incubation. Factor VIII:C was 4%, and the titer for factor VIII inhibitor was 9 Bethesda units. Three months later, after a retroperitoneal hemorrhage, a lymphocytosis was found in her peripheral blood with morphological and surface immunophenotype characteristics of B-cell chronic lymphocytic leukemia, later confirmed by bone marrow morphological and immunocytochemical examinations. To our knowledge, this is the first report of an autoimmune factor VIII inhibitor associated with chronic lymphocytic leukemia.