Lupus Anticoagulant-hypoprothrombinemia Syndrome Research Articles

Lupus anticoagulant-hypoprothrombinemia syndrome presenting with co-existing cerebral venous thrombosis and subdural hemorrhage

The lupus anticoagulant-hypoprothrombinemia syndrome (LA-HPS)-the association of acquired factor II deficiency and lupus anticoagulant-is a rare disease that may cause a predisposition not only to thrombosis but also to severe bleeding. We are reporting on a 36-year-old female patient presenting with co-existing cerebral venous thrombosis and subdural hemorrhage. The coagulation screening showed a prolonged prothrombin time (PT), activated partial thromboplastin time (aPTT), and a normal fibrinogen level and platelet count. Evaluation of the clotting factors revealed decreased levels of factors II (37%). Factors V, VIII, IX and XI were normal. Lupus anticoagulant (LA) was demonstrated by the Dilute Russell's Viper Venom Test (DRVVT). Immunological work-up was positive for IgG type anticardiolipines antibodies (aCL). Successful management consisted first of oral prednisone (60mg/d). Thus, anticoagulation was introduced once factor II had stabilized.

Lupus anticoagulant-hypoprothrombinemia syndrome and catastrophic antiphospholipid syndrome in a patient with antidomain I antibodies

Lupus anticoagulant-hypoprothrombinemia syndrome is a rare condition characterized by the association of acquired factor II deficiency and lupus anticoagulant. Contrary to classical antiphospholipid syndrome, it may cause severe life-threatening bleeding (89% of published cases). We report a patient, positive for antidomain I antibodies, with initially primary lupus anticoagulant-hypoprothrombinemia syndrome without previous clinical manifestation or underlying systemic disease. Five years later, he experienced the first systemic lupus erythematous flare. Within a few days, catastrophic antiphospholipid syndrome was diagnosed with heart, liver and kidney involvement. The patient recovered under pulse steroids, intravenous heparin and intravenous immunoglobulins.

Early Detection of Lupus Anticoagulant-Hypoprothrombinemia Syndrome By Rotational Thromboelastometry

Lupus anticoagulant-hypoprothrombinemia syndrome (LA-HPS) is a rare disorder characterized by association of acquired factor II deficiency and lupus anticoagulant that may cause predisposition to both thrombosis and bleeding. The hemorrhagic episodes are caused by non-neutralizing antibodies directed against prothrombin, resulting in rapid clearance of the antigen-antibody complexes. It is most commonly seen in pediatric population, with a total of less than 100 reported cases in literature. Early diagnosis of LA-HPS is critical, as it may result in fatal complications if not identified early and treated appropriately. Here we present two cases of LA-HPS where Rotational Thromboelastometry (ROTEM) aided early diagnosis.Case one:A 28 year-old woman with history of systemic lupus erythematosis (SLE) , anti phospholipid antibody syndrome, and pulmonary embolism presented from an outside facility with spontaneous subdural hematoma. Warfarin therapy had been discontinued 18 days prior to her presentation secondary to bilateral lower extremity hematomas. The INR was 3.59 at the outside facility, for which she received prothrombin complex concentrates and Vitamin K. Laboratory values at time of admission included prothrombin time (PT) of 16.3 seconds, INR of 1.34 and partial thromboplastin time (PTT) of 53 seconds; the patient received an additional two units of plasma after admission. Despite these interventions, the INR increased to 2.02 on day two of hospitalization. At this time, ROTEM was performed which revealed a markedly prolonged EXTEM clotting time (CT) at 502 seconds (reference range: 43 s-82 s) and INTEM CT at 395 s (reference range: 122 s-208 s). Further investigation revealed decreased factor II activity at 6%, with all other Vitamin K dependent factors within reference range. Lupus-like inhibitor was positive and anti-prothrombin antibodies were elevated at 102.6 units (reference range 0.0-19.9 units), confirming the diagnosis of LA-HPS, after which the patient was treated with high dose corticosteroids and cyclophosphamide. PT and APTT decreased to 1.32 and 36 respectively on day two of immunosuppressive therapy. No neurosurgical intervention was undertaken, given the stability of the subdural hematoma and the patient's clinical improvement.Case two:A 42 year-old woman with a history significant for lupus anticoagulant presented with symptomatic anemia and hemoperitoneum. Her initial labs included a PT of 16.8 seconds and INR of 1.40 with a PTT of 55 seconds. Exploratory laparotomy revealed two liters of hemoperitoneum arising from a hemorrhagic ovarian cyst. The patient received 654 ml of plasma intraoperatively. A postoperative ROTEM was notable for markedly prolonged INTEM CT (363 seconds) and EXTEM CT (341 seconds). Postoperative PT and PTT were 15.5 seconds and 55 seconds, respectively. Further investigation revealed decreased Factor II activity at 42%; factor V and factor VII activity were within reference range. Elevated anti-prothrombin IgG antibodies (54.6 units; reference range 0.0-19.9 units) and IgM antibodies (28.2 units; reference range 0.0-19.9units) confirmed the diagnosis of LA-HPS. In this case corticosteroids were not administered to the patient given Factor II activity of more than 40 %. The patient's clinical status improved and she was discharged five days later without further sequelae. Outpatient evaluation performed weeks after discharge showed positive antibodies to Cardiolipin and beta-2-glycoprotein-1.Conclusion:In both presented cases, the prolongation of the INTEM and EXTEM CT was greater than what the PT and PTT would predict and appear to be an inhibitory pattern. The effects of lupus anticoagulants and anti-prothrombin antibodies on ROTEM has not yet been described in the literature. These cases illustrate the potential of thromboelastometry in early detection of LA-HPS; further investigation of the impact of lupus anticoagulants on ROTEM analysis is warranted. DisclosuresLockhart:Octapharma: Honoraria, Other: Travel and housing support to speaking engagements.., Speakers Bureau; TEM Systems, Inc.: Consultancy, Honoraria, Other: Travel and housing support to consultancy meetings, reagent support for research., Speakers Bureau; Bayer: Consultancy, Other: Travel and housing support to consultancy meetings.; CSL Behring: Consultancy, Honoraria, Other: Travel and housing support to consultancy meetings..

Lupus Anticoagulant-hypoprothrombinemia Syndrome that did not Progress to Systemic Lupus Erythematosus: A Case Report

Lupus anticoagulant-hypoprothrombinemia syndrome (LA-HPS) is a rare disorder, and appears mostly in children. The primary concern is its potential development into systemic lupus erythematosus (SLE). A 5-year-old patient was hospitalized with multiple purpuric lesions. A markedly prolonged prothrombin time and activated partial thromboplastin time were observed and were not corrected after mixing with normal plasma. Decreased factor II activity was consistent with LA-HPS. Identifying risk factors that play an important role in the development of SLE in patients with LA-HPS is of importance. Based on the case described here, anti-double stranded (ds) DNA antibody and the Sapporo criteria for antiphospholipid syndrome are related to subsequent SLE development, whereas there is no correlation with the results of the lupus anticoagulant (LA) test. We recommend an early and serial examination of anti-ds DNA antibody and full evaluation of Sapporo criteria for the screening of patients with LA-HPS who may progress to SLE.

The challenge of bleeding in antiphospholipid antibody-positive patients.

Antiphospholipid antibody-positive patients can develop bleeding due to capillaritis, microthrombosis, antiprothrombin antibodies, thrombocytopenia, and/or excessive antithrombotic therapy. Clinical characteristics of patients, e.g., renal impairment, elderly, or concomitant medications, are closely related to the risk of bleeding. The management of bleeding in antiphospholipid antibody (aPL)-positive patients is challenging due to the baseline increased risk of thrombosis. If anticoagulation is stopped, it should be restarted as soon as possible once the acute bleeding is controlled; the continuation of anticoagulation despite active bleeding may be required in selected cases. High-dose corticosteroid is the mainstay treatment for diffuse alveolar hemorrhage, lupus anticoagulant-hypoprothrombinemia syndrome, and severe thrombocytopenia; immunosuppressive drugs are also required to improve the long-term outcomes. Hydrocortisone is critical in adrenal hemorrhage patients due to concomitant adrenal insufficiency; despite bleeding, anticoagulation should be maintained as much as possible. Plasma exchange should be considered in catastrophic antiphospholipid syndrome patients with concurrent bleeding. This article will review the causes of bleeding in aPL-positive patients as well as the management strategies.

Lupus Anticoagulant-hypoprothrombinemia Syndrome as an Initial Manifestation of Systemic Lupus Erythematosus: A Case Report

The lupus anticoagulant-hypoprothrombinemia syndrome, characterized by presence of lupus anticoagulant with acquired factor II deficiency, is a rare disease entity often presented with acute bleeding episodes. A 15-year-old girl was hospitalized with 3 month history of menorrhagia and easy bruising. Prothrombin time (31.3 sec, normal value: 10-13 sec) and activated partial thromboplastin time (72.5 sec, normal value: 27.5-34.7 sec) were markedly prolonged and partially corrected after mixing with normal plasma. Decreased Factor II activity (4%, normal range: 79-131%) or prolonged dilute Russell’s viper venom time (89.8 sec, normal value: 25.4-34.3 sec), was consistent with lupus anticoagulant-hypoprothrombinemia syndrome. Antinuclear antibody, anti-double strand-DNA antibodies and anticardiolipin antibodies were also positive. Bleeding diathesis tends to wax and wane while 5 years of treatment with steroid combined with immunosuppressants, however, there was no more active bleeding episodes. Several years after diagnosis, myocarditis, pericarditis, seizure was occurred, fulfilled the diagnostic criteria of systemic lupus erythematosus. pISSN 2233-5250 / eISSN 2233-4580 http://dx.doi.org/10.15264/cpho.2014.21.2.145 Clin Pediatr Hematol Oncol 2014;21:145∼148

Pulmonary hemorrhage in pediatric lupus anticoagulant hypoprothrombinemia syndrome.

Lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS), a very rare disease that is caused by the presence of antifactor II antibodies, is usually counterbalanced by the prothrombotic effect of lupus anticoagulant (LAC). Patients with LAHPS are treated using fresh frozen plasma, steroids, immunosuppressive agents, and immunoglobulins for managing the disease and controlling hemorrhages. Notably, steroids are the important treatment for treating hypoprothrombinemia and controlling the bleeding. However, some patients suffer from severe, life-threatening hemorrhages, when factor II levels remain very low in spite of treatment with steroids. Here, we report a case of LAHPS in a 15-year-old girl who experienced pulmonary hemorrhage with rapid progression. She was referred to our hospital owing to easy bruising and prolonged bleeding. She was diagnosed with LAHPS that presented with pancytopenia, positive antinuclear antibody, proloned prothrombin time, activated partial thromboplastin time, positive LAC antibody, and factor II deficiency. Her treatment included massive blood transfusion, high-dose methylprednisolone, vitamin K, and immunoglobulin. However, she died due to uncontrolled pulmonary hemorrhage.

Lupus anticoagulant hypoprothrombinemia syndrome in Bence-Jones protein κ-type multiple myeloma patient with phosphatidylserine-dependent antiprothrombin antibody

Dear Editor, Approximately 2 % of multiple myeloma (MM) patients present with hemorrhage at diagnosis. However, hemorrhage due to abnormalities in the coagulation system is a rare complication [1, 2]. Although lupus anticoagulant (LA), which is infrequently reported to be in association with MM, is commonly a risk factor for arterial or venous thrombosis, bleeding tendencies in patients with LA are strongly related to a low prothrombin activity [3–6]. Acquired hypoprothrombinemia with LA, also called LA hypoprothrombinemia syndrome (LAHPS), is a rare disease which appears mostly in young females with systemic lupus erythematosus or in healthy children after viral infection and is usually associated with the presence of antiprothrombin antibodies [7]. We herein report the case of an 86-year-old male with Bence-Jones protein (BJP) κ-type MM who presented with hypoprothrombinemia and LA associated with antibodies directed to the phosphatidylserine–prothrombin complex (or phosphatidylserine-dependent antiprothrombin antibodies, aPS/PT). The patient was admitted with anemia and had no past history of bleeding disorders or thrombotic events. A urinalysis showed massive proteinuria (5.3 g/day), which was determined to be κ-type BJP using immunoelectrophoresis. Bone marrow aspiration showed proliferation of abnormal plasma cells. Computerized tomography showed hematomas in the bilateral gluteus maximus muscle and the supraclavicular area. Initial coagulation tests showed prolonged prothrombin time and activated partial thromboplastin time (aPTT) (Table 1). Reduced clotting activity of factors II (FII), VIII (FVIII), and IX (FIX) was noted in a pattern typical of that observed in previously reported cases of LAHPS [8, 9]. FVIII and FIX inhibitors were not detected. The prolonged aPTT with LA-sensitive aPTT reagent (PTT-LA Roche Diagnostics, Tokyo, Japan), which could not be corrected by mixing with normal plasma, suggested the presence of LA. The results were confirmed using the Staclot LA® assay, and the dilute Russell viper venom time test was used to confirm the presence of LA with the phospholipid-neutralizing LA test (Gradipore, Frenchs Forest, Australia). IgG/M anticardiolipin antibodies and IgG aPS/PT were negative, while strong positive IgM aPS/PT was detected, which was measured with ELISA using the phosphatidylserine–prothrombin complex as antigen immobilized on ELISA plates in the presence of CaCl2 [10]. Based on these findings, the patient was diagnosed as MM with LAHPS associated with aPS/PT and treated with melphalan and prednisolone (MP) therapy. The FII levels were observed to normalize after one cycle of MP therapy and the patient has remained in remission without any hemorrhage for 10 months. Table 1 Laboratory findings In our case, aPTT continued to be prolonged with reduced levels of FVIII and FIX in spite of normalizing the FII level after therapy. LA and IgM aPS/PT remained positive, although these values were improved, suggesting that the presence of LA might have an influence on coagulation tests after treatment. There are very rare reports showing the presence of aPS/PT in patients with LAHPS [9]. These reports describe the patients as having bleeding tendencies with mildly reduced FII levels, similar to that observed in our patient. However, in previously reported child cases of LAHPS, severe hemorrhage usually occurs when the FII levels are very low (under 10∼15 %). It is possible that other coagulation factors associated with aPS/PT in LAHPS might be present. A diagnosis of LAHPS should always be considered in MM patients with bleeding tendencies associated with LA, and aPS/PT detection should be performed in conjunction with LA tests.

Resolution of Hypoprothrombinemia‐Lupus Anticoagulant Syndrome (HLAS) after multidrug therapy with rituximab: a case report and review of the literature

Hypoprothrombinemia associated with a lupus anticoagulant (LA) was first reported in the literature over 50years ago. The hypoprothrombinemia-lupus anticoagulant syndrome (HLAS) is a rare bleeding diathesis that has been associated with LAs in adult and paediatric patients with systemic lupus erythematosus (SLE) and with transient LAs due to other causes. There are no standard recommendations for treating haemorrhage associated with this syndrome. Herein, we report a patient with SLE and HLAS who achieved a durable remission following treatment with intravenous immune globulin (IVIG), prednisone and rituximab.

Lupus Anticoagulant-Hypoprothrombinemia Syndrome

The lupus anticoagulant-hypoprothrombinemia syndrome (LAHS)--the association of acquired factor II deficiency and lupus anticoagulant--is a rare disease drastically different from antiphospholipid syndrome in that it may cause predisposition not only to thrombosis but also to severe bleeding. We performed a retrospective study of 8 patients with LAHS referred to 6 French tertiary care centers between January 2003 and February 2011, and a literature review retrieving all related articles published between 1960 and April 2011. Including our 8 new cases, LAHS has been reported in 74 cases. The disease mostly occurs in young adults, with a female to male sex ratio of 1.4. Associated conditions mostly include autoimmune diseases such as systemic lupus erythematosus and infectious diseases. Bleeding is a frequent feature (89% of cases), while arterial and/or venous thrombosis is less common (13%). Factor II level is severely decreased at diagnosis (median value, 11%; range, 1%-40%). LAHS associated with autoimmune diseases is more persistent than LAHS associated with infection, and hemorrhagic complications are more common. Corticosteroids should be considered the first-line treatment, but the thrombotic risk strongly increases during treatment because of the improvement of factor II level. Despite the fact that 50% of patients develop severe bleeding, the mortality rate is <5%, after a median follow-up of 13 months (range, 0.5-252 mo). LAHS associated with autoimmune diseases should be diagnosed and managed carefully because the disease is persistent and severe hemorrhagic complications are common.

Lupus anticoagulant-hypoprothrombinemia syndrome revealing systemic lupus in an 11-year old girl in a context of clinical and biological emergency

We report a case of lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS) in an 11 year old girl initially hospitalized for bleeding. The patient presented with petechia, persisting bleeding after tooth extraction performed two days before, nephritic syndrome (renal failure, proteinuria and macroscopic hematuria), severe anemia, thrombocytopenia, lymphopenia. The association of these abnormalities suggested LAHPS secondary to severe systemic lupus. Immediate treatment with fresh frozen plasma and intravenous immunoglobulins (400mg/kg/5d) was started and followed by steroid (500mg/d) and cyclophosphamide (800mg/m(2)) pulse therapy leading to rapid improvement of bleeding, renal involvement and prothrombin levels within 13 days. Lupus diagnosis was confirmed by immunological investigations and renal biopsy. Two early relapses occurred despite adequate treatment. After a follow-up of two years, no further disease activity is noted while the patient is treated only by mycophenolate mofetil (1 200mg/m(2)/d). LAHPS did not relapse during this follow-up.

Lupus anticoagulant-hypoprothrombinemia syndrome with a false-positive test for coagulation factor inhibitors

Lupus anticoagulant-hypoprothrombinemia syndrome with a false-positive test for coagulation factor inhibitors

Steady improvement of prothrombin levels after cyclophosphamide therapy in pediatric lupus anticoagulant hypoprothrombinemia syndrome (LAHPS)

Lupus anticoagulant hypoprothrombinemia syndrome (LAHPS) is a rare acquired disorder associated with several different conditions but mostly with systemic lupus erythematosus (SLE). LAHPS probably results from the presence of anti-Factor II antibodies, which usually counterbalance the prothrombotic effect of the lupus anticoagulant (LAC). In fact, Factor II deficiency in SLE is invariably associated with the presence of LAC. No consensus exists for the treatment of LAHPS. Corticosteroids, with or without the addition of vitamin K or blood products, have been a successful first-line treatment. Immunoglobulin (IVIG) treatment has been shown to be effective in the setting of acute bleeding. However, in some patients, conservative treatment is not enough to control bleeding, and the addition of immunosuppressive therapy, usually azathioprine, is needed. In our patients, Factor II deficiency reappeared after tapering steroids. Both children achieved normal Factor II levels with cyclophosphamide. This effect was long-lasting, a phenomenon that has not been documented in children prior to this report.

Pre-operative management of a patient with hypoprothrombinemia-lupus anticoagulant syndrome

Pre-operative management of a patient with hypoprothrombinemia-lupus anticoagulant syndrome -

Clinicohematologic Spectrum in Patientswith Lupus Anticoagulant

A retrospective analysis of clinicohematologic parameters of 25 patients with lupus anticoagulant was carried out. The hematologic tests included dilute Russel viper venom test (dRVVT), kaolin clotting time (KCT), activated partial thromboplastin time, and prothrombin time. The diagnosis of lupus anticoagulants was based on the presence of prolonged KCT/dRVVT, its absence of correction with normal plasma and correction by phospholipids. Specific factor assays and platelet aggregation studies were performed wherever required. Ten patients (40%) had thrombosis, which was venous in 5 (50%) and arterial in 4 (40%). One patient (10%) had both arterial and venous thrombosis and presented with catastrophic antiphospholipid syndrome. Eighteen female patients conceived. Four (22%) of these had recurrent first trimester abortion. Five (20%) patients had bleeding manifestations. One (4%) of these had hypoprothrombinemia and was diagnosed to have hypoprothrombinemia lupus anticoagulant syndrome. However in two of these patients, no cause of bleeding could be identified other than the presence of lupus anticoagulants. It is concluded that patients with lupus anticoagulant have a varied spectrum of hemostatic disorders. Bleeding may sometimes occur in these patients due to associated thrombocytopenia or associated factor inhibitors. Rarely, it may occur due to presence of lupus anticoagulants alone.

Acquired Hypoprothrombinemia Lupus Anticoagulant Syndrome Developed in a Healthy Child

Acquired Hypoprothrombinemia Lupus Anticoagulant Syndrome Developed in a Healthy Child

Transient hemorrhagic diathesis associated with an inhibitor of prothrombin with lupus anticoagulant in a 1½-year-old girl: Report of a case and review of the literature

Acquired inhibitors of coagulation causing bleeding manifestations are rare in children, particularly without an associated underlying disorder such as autoimmune disease. We describe an otherwise healthy 1 1/2-year-old girl who had extensive spontaneous bruising and prolonged bleeding from venipuncture sites. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged, with evidence of an immediate-acting inhibitor. Thrombin clotting time, fibrinogen, and platelets were normal. Biologic assay of factors II, V, VII, and X were all low, with increasing values at higher dilutions. However, by immunoassay and/or chromogenic assays, only factor II was reduced. An antibody which failed to neutralize prothrombin activity in vitro was detected against radiolabeled prothrombin. Coagulation studies normalized in parallel with clinical recovery and disappearance of the antibody. This case demonstrates acute hypoprothrombinemia-lupus anticoagulant syndrome as a rare presentation of bleeding diathesis in a healthy young child.

Correction of hypoprothrombinemia by immunosuppressive treatment of the lupus anticoagulant-hypoprothrombinemia syndrome

A 66-year-old man with the lupus anticoagulant-hypoprothrombinemia syndrome was treated with cyclophosphamide and prednisone to correct a factor II deficiency prior to elective major surgery. Whereas the lupus anticoagulant activity persisted, functional factor II levels normalized and he underwent surgery without a bleeding diathesis. Immunosuppressive therapy may temporarily normalize factor II levels in patients with the lupus anticoagulant-hypoprothrombinemia syndrome and reduce the risk of excessive hemorrhage. The disparate response of the lupus anticoagulant and hypoprothrombinemia to immunosuppression suggests that the lupus anticoagulant did not directly cause the hypoprothrombinemia.

A Mechanism for the Hypoprothrombinemia of the Acquired Hypoprothrombinemia-Lupus Anticoagulant Syndrome

Antibodies that bind prothrombin without neutralizing its coagulant activity were demonstrated in the plasma of two patients with the acquired hypoprothrombinemia-lupus anticoagulant syndrome. The first patient's plasma contained less than 1% prothrombin activity and no detectable prothrombin antigen. The second patient's plasma contained about 6% of both prothrombin activity and antigen. Neither patient's plasma neutralized the prothrombin coagulant activity of normal plasma or of purified prothrombin added in vitro. Nevertheless, double immunodiffusion studies and binding experiments utilizing 125I-prothrombin demonstrated the presence of prothrombin antibodies in each patient's plasma. A Scatchard analysis of the binding data obtained with different concentrations of 125I-prothrombin and the first patient's plasma indicated the presence of a high affinity antibody, apparent Kd approximately 10(-10)M, and a lower affinity antibody, apparent Kd approximately 10(-9)M. Studies utilizing purified cleavage products of prothrombin suggested that the antibodies were directed against an epitope or epitopes located on the carboxyl-terminal, latent thrombin segment of the prothrombin molecule. We postulate that the acquired hypoprothrombinemia in these two patients and in other reported patients with the acquired hypoprothrombinemia-lupus anticoagulant syndrome stems from rapid clearance from the circulation of prothrombin antigen-antibody complexes.

A mechanism for the hypoprothrombinemia of the acquired hypoprothrombinemia-lupus anticoagulant syndrome

Antibodies that bind prothrombin without neutralizing its coagulant activity were demonstrated in the plasma of two patients with the acquired hypoprothrombinemia-lupus anticoagulant syndrome. The first patient's plasma contained less than 1% prothrombin activity and no detectable prothrombin antigen. The second patient's plasma contained about 6% of both prothrombin activity and antigen. Neither patient's plasma neutralized the prothrombin coagulant activity of normal plasma or of purified prothrombin added in vitro. Nevertheless, double immunodiffusion studies and binding experiments utilizing 125I- prothrombin demonstrated the presence of prothrombin antibodies in each patient's plasma. A Scatchard analysis of the binding data obtained with different concentrations of 125I-prothrombin and the first patient's plasma indicated the presence of a high affinity antibody, apparent Kd approximately 10(-10)M, and a lower affinity antibody, apparent Kd approximately 10(-9)M. Studies utilizing purified cleavage products of prothrombin suggested that the antibodies were directed against an epitope or epitopes located on the carboxyl-terminal, latent thrombin segment of the prothrombin molecule. We postulate that the acquired hypoprothrombinemia in these two patients and in other reported patients with the acquired hypoprothrombinemia-lupus anticoagulant syndrome stems from rapid clearance from the circulation of prothrombin antigen-antibody complexes.