Acquired factor V inhibitors

Medication-Induced Factor V Inhibition in the Setting of Refractory Coagulopathy

Liver cirrhosis is commonly associated with coagulopathies, typically demonstrated by elevated prothrombin time, international normalized ratio, and partial thromboplastin time. In the setting of bleeding related to coagulopathies, oftentimes physicians try to reverse coagulopathy through a variety of methods including the use of vitamin K and fresh frozen plasma. Rarely, attempts at reversing coagulopathy are unsuccessful due to severe disease or factor inhibitors. The treatment of acquired factor V inhibitors is primarily performed through immunosuppression and supportive care for the initial bleeding episode. Early detection and treatment of factor V inhibition is challenging in a setting of underlying cirrhosis-related coagulopathy.

Acquired Factor V Inhibitor Complicated with Immune Thrombocytopenia

We herein report a patient with a high bleeding tendency as a result of acquired factor V inhibitor and immune thrombocytopenia (ITP). The administration of prednisolone increased the platelet count, but a fatal bleeding event occurred before platelet levels had sufficiently increased. Factor V is stored in not only plasma but also platelets, and platelet-derived factor V might play a local hemostatic role. Bleeding tendency may be high in rare cases where factor V inhibitor is complicated with severe thrombocytopenia. In such patients, physicians should consider aggressive hemostatic therapy, including plasma exchange, in addition to immunosuppressive therapy.

A Review of Coagulation Abnormalities of Autoimmune Acquired Factor V Deficiency with a Focus on Japan

Coagulation factor V (or FV for the purpose of medical safety) is an essential cofactor of coagulation factor X in the common pathway of coagulation; severe FV deficiency leads to a bleeding tendency. Although both congenital and acquired FV deficiencies are widely recognized, FV deficiency also presents as an autoimmune disorder. A nationwide survey on autoimmune coagulation factor deficiencies (AiCFDs) conducted in Japan by our Japanese Collaborative Research Group identified 24 new patients with autoimmune FV deficiency (AiFVD) in the past 5 years. Furthermore, our extensive literature search confirmed that 177 AiFVD cases have been reported in previous articles published from Japan. Patients with AiFVD in Japan were predominantly men, with age similar to those with other AiCFDs. AiFVD was confirmed as a relatively mild type of bleeding diathesis, associated with lower mortality rate than that for AiFVD and other AiCFDs reported in previous studies. Patients with AiFVD had variable FV inhibitor titers and both neutralizing anti-FV autoantibodies and nonneutralizing counterparts. Although spontaneous resolution occurs in some patients, timely initiation of hemostatic and immunosuppressive therapies helps arrest the bleeding and eliminate anti-FV antibodies, resulting in a high cumulative recovery rate. Immunological anti-FV antibody detection is recommended to avoid missing AiFVD cases for the presence of nonneutralizing anti-FV autoantibodies. Further investigation is necessary to clarify the long-term prognosis and optimal management of AiFVD.

Acquired factor V inhibitor: Success of steroids in a patient with primary sclerosing cholangitis, ulcero haemorragic rectocolitis, biological Biermer's disease

We report the case of a 43-years-old Turkish man with acquired deficiency of factor V (FV) diagnosed in a usual screening before a (recto) colonoscopy. In the biologic explorations, activated partial prothrombin time (APTT) was abnormally high and prothrombin time (PT) was low 18IU/dL with no anticoagulant drugs (the PT was normal 6 months ago). The controlled level of factor V was 3IU/dL with FV antibodies (9 Bethesda Units/mL). This patient had a previous history of primary sclerosing cholangitis (2000) and ulcero haemorrhagic rectocolitis (2002) and a fortuitous biological Biermer's disease was revealed. Corticosteroids were prescribed at 1mg/kg/day with decreasing during 6 months, patient had gradual regression of the caused bleeding and FV became greater than 90%, F V antibodies decreased to less than 0.7 Bethesda Units/mL. This case illustrates the presence of FV inhibitor in an autoimmune gastrointestinal context with regression of clinical (caused) signs and antibodies with corticosteroids.

Acquired factor V inhibitor: a nation-wide study of 38 patients

Acquired factor V inhibitor (AFVI) is an extremely rare disorder that may cause severe bleeding. To identify factors associated with bleeding risk in AFVI patients, a national, multicentre, retrospective study was made including all AFVI patients followed in 21 centres in France between 1988 and 2015. All patients had an isolated factor V (FV) deficiency <50% associated with inhibitor activity. Patients with constitutional FV deficiency and other causes of acquired coagulation FV deficiencies were excluded. The primary outcome was incident bleeding and factors associated with the primary outcome were identified. Thirty-eight (74 [36-100] years, 42·1% females) patients with AFVI were analysed. Bleeding was reported in 18 (47·4%) patients at diagnosis and in three (7·9%) during follow-up (7 [0·2-48.7] months). At diagnosis, FV was <10% in 31 (81·6%) patients. Bleeding at diagnosis was associated with a prolonged prothrombin time that strongly correlated with the AFVI level measured in plasma {r = 0·63, 95% confidence interval (CI) [0·36-0·80], P < 0·05}. Bleeding onset during follow-up was associated with a slow AFVI clearance (P < 0·001). The corresponding receiver operating characteristics curve showed that AFVI clearance was predictive of bleeding onset with an AFVI clearance of seven months with a sensitivity of 100% (95% CI: 29-100) and a specificity of 86% (95% CI: 57-98, P = 0·02). Kaplan-Meier analysis showed that AFVI clearance >7 months increased the risk of bleeding by 8 (95% CI: [0·67-97], P = 0·075). Prothrombin time at diagnosis and time for clearance of FV inhibitor during follow-up are both associated with bleeding in patients with AFVI.

Development of Acquired Factor V Inhibitor After Surgical Procedure Without the Use of Fibrin Tissue Adhesives: A Case Report

Development of acquired factor V (FV) inhibitor is a rare coagulation disorder. Production of heteroantibodies against bovine FV, a contaminant in fibrin tissue adhesives, is a common cause of this condition in the field of surgery. The development of recombinant thrombin eliminated contamination of bovine FV, and infrequent use of bovine thrombin has decreased the risk of FV inhibitor development. Here, we report the case of a 43-year-old man who had marked prolongation of prothrombin time and activated partial thromboplastin time after surgery. Mixing coagulation studies with normal plasma and patient’s plasma suggested the presence of an inhibitor. Clotting factor assays revealed that FV activity decreased to <1% with positive FV inhibitor titer (9.2 Bethesda units). The diagnosis of the FV inhibitor was confirmed. Overt bleeding was not observed during the course of hospitalization. His coagulation abnormalities rapidly normalized without any medical intervention. A careful review of his medical records revealed that no tissue adhesives were used in the patient, and the FV inhibitor would likely be autoantibodies. Antibiotic use during the perioperative period or the surgical procedure itself may trigger the occurrence of FV inhibitors. This case highlights that FV inhibitor may develop after the surgical procedure even without a history of the use of fibrin tissue adhesives. Surgeons and hematologists should be aware that this rare but potentially life-threatening condition may occur after the surgical procedure.

Successful Management of Life-threatening Pelvic Hemorrhage From Acquired Factor V Deficiency With immunosuppressive Therapy

Acquired Factor V deficiency is a rare and challenging condition to treat. It has been associated with major surgeries, antibiotics, blood transfusions, infections, autoimmune disorders, malignancy and exposure to bovine thrombin. The clinical presentation can be heterogeneous and can manifest as asymptomatic laboratory abnormalities to fatal hemorrhage with mortality rates around 15-20% . We report a case of acquired factor V deficiency in which the patient developed a life-threatening bleeding coagulopathy with elevated prothrombin time, activated partial thromboplastin time and factor V inhibitor titers following multiple surgical procedures that were performed after a motor vehicle accident. The patient was successfully treated with immunosuppressive therapy including steroids and cyclophosphamide resulting in the complete elimination of inhibitor levels.

Plasma Exchange as an Initial Treatment for Severe Bleeding Induced by Acquired Factor V Deficiency: A Case Report and Mini Literature Review

Acquired factor V deficiency (AFVD) is a rare autoimmune bleeding disorder. Unlike acquired hemophilia, bypass therapies with recombinant activated factor VII and activated prothrombin complex concentrates are ineffective for severe bleeding due to AFVD. Although several treatment strategies have been attempted, a standard of care for severe hemorrhage induced by AFVD is lacking. Herein, we report a case of AFVD with severe bleeding that responded to plasma exchange (PE) combined with immunosuppression. We also reviewed previously reported AFVD cases with severe hemorrhage and suggest that PE may be an effective initial treatment for AFVD-induced severe hemorrhage.

Acquired Factor V Inhibitor After Antibiotic Therapy: A Clinical Case Report and Review of the Literature

Acquired factor V inhibitor (aFVi) is an exceptionally rare hematologic condition that can range from incidental laboratory abnormalities to life-threatening hemorrhage. Bovine thrombin was formerly the most common cause of this condition; however, the decreased use of bovine thrombin in surgical procedures has led to a shift in the cause of aFVi toward antibiotic use and malignancies. Here we present a case of an 80-year-old Caucasian female on long-term warfarin therapy who presented with epistaxis and an elevated international normalized ratio, and a history of cephalosporin antibiotic use. We review the published literature beginning in 2016 to identify the evolving causes of aFVi. Additionally, we propose that stress-mediated immune regulation may contribute to antibody formation, preventing the interaction between factor V and the damaged phospholipid membranes. This case highlights the evolving causes of aFVi and should prompt physicians to consider this diagnosis in coagulopathies that do not correct with traditional therapies.

Acquired factor V inhibitors after allogeneic hematopoietic stem cell transplantation in a dog

Objective

Describe the clinical course and management of a dog that underwent hematopoietic stem cell transplantation (HSCT) for treatment of B‐cell lymphoma and developed acquired circulating factor V (FV) inhibitors.

Case Summary

An 8‐year‐old male castrated Briard dog diagnosed with lymphoma (IVb, B‐cell) presented for allogeneic HSCT. Despite multiple platelet, fresh frozen plasma, and red blood cell transfusions prolonged recovery and clinical bleeding occurred. Circulating acquired FV inhibitors were identified and hemorrhage subsequently was managed by immunosuppression. The dog was discharged when clinical resolution of bleeding was achieved.

New or Unique Information Provided

This case report describes a dog undergoing curative intent treatment for lymphoma, and subsequently acquiring factor inhibition, and was successfully managed. Specific coagulation screening to assess for coagulation factor deficiencies or inhibitors is essential in the diagnosis and treatment of patients with refractory bleeding or only transient response to blood transfusion.

A high titer of acquired factor V inhibitor in a hemodialysis patient who developed arterial thrombosis

An 87-year-old man with diabetes mellitus was admitted to control recurrent bleeding from hemodialysis puncture sites. He was a smoker and had been diagnosed with arteriosclerosis obliterans. His PT and APTT were markedly prolonged, and all coagulation factors were markedly decreased (factor V [FV] activity < 1%) or below the measurement threshold, with the exception of fibrinogen and factor XIII. Neither PT nor APTT were corrected upon mixing with normal plasma. A high titer of FV inhibitor was found at 415 BU/mL, and anti-FV autoantibody was detected by both immunoblot assay and ELISA. Prednisolone administration and plasma exchange partially improved prolonged PT and APTT and decreased the FV inhibitor level. Five months later, he manifested symptoms of severe ischemia in both legs. Angiography revealed diffuse stenosis downstream of both common iliac arteries. Endovascular therapy was repeated four times, the prednisolone dose was reduced, and low-dose antiplatelet therapy was initiated. After the final successful endovascular therapy, arterial thrombosis was detected using ultrasound and angiography. Aspiration thrombectomy and thrombolytic therapy failed to achieve recanalization, and necrosis of the legs worsened. Despite the severe coagulation abnormalities, vascular interventions should have been performed with regular-dose antiplatelet therapy, as the patient exhibited multiple risk factors for atherothrombosis.

Successful Outcome of Severe Intra-cerebral Bleeding Associated with Acquired Factor V Inhibition: Utilization of Multiple Therapeutic Agents

Background:

Acquired coagulation factor inhibitors are antibodies that either inhibit activity or increase the clearance of a clotting factor and lead to an increased risk of bleeding. Most of the time, the disorder is attributed to factor VIII inhibition (acquired haemophilia A); however, other coagulation factors could also be implicated.

Case Report:

Herein, we report an interesting case of a patient who underwent coronary artery bypass grafting and received antibiotic treatment after surgery with third generation cephalosporin. A month later, he presented with extreme bleeding diathesis and cerebral haemorrhage. Following a thorough clinical and laboratory investigation, an acquired factor V inhibitor was diagnosed. The patient received treatment with corticosteroids, intravenous immunoglobulins, anti-CD20 monoclonal antibodies (rituximab), cyclophosphamide and recombinant factor VIIa. Finally, despite the poor initial prognosis, the patient managed to achieve a full recovery.

Conclusion:

As there are no clear guidelines on acquired coagulation inhibitor treatment, reports of such cases could offer insight for future therapy choices. The case was unique because the treatment regimen included a combination of multiple therapeutic agents including rituximab.

Acquired factor V deficiency following transcatheter arterial chemoembolization for hepatocellular carcinoma: a case report

Acquired factor V deficiency is a rare condition associated with a wide variety of causes. We herein report the case of a 75-year-old man who developed acquired factor V deficiency associated with gastrointestinal bleeding after transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma. Laboratory data revealed prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT) and a significant reduction in the factor V (FV) activity. Infusion of fresh-frozen plasma (FFP) was unable to correct the prolonged PT and APTT. Four weeks after onset, his coagulation parameters improved spontaneously with no particular treatment. The patient developed acquired FV deficiency after TACE treatment using cisplatin, and thus, cisplatin was suspected as the cause of this coagulopathy. If coagulopathy that is not corrected by FFP transfusion after TACE is observed, acquired factor V deficiency, although extremely rare, should be considered.

Acquired Inhibitors to Multiple Coagulation Factors (V, IX, and XII) Identified in a Unique Patient with Hepatocellular Carcinoma

An acquired formation of inhibitors to coagulation factors is a rare type of coagulopathy. The development of inhibitors for multiple coagulation factors has never been reported. A 75-year-old Japanese female underwent interventional therapy for hepatocellular carcinoma. Five days after the last intervention, her prothrombin time decreased to 10%, and her activated partial thromboplastin time (APTT) lengthened to 265.1 sec. The activities for coagulation factors showed significantly reduced activities (<10%) of factors V, IX, and XII. A cross-mixing test demonstrated an inhibitor pattern, and inhibitory antibodies against factors V, IX, and XII were detected. We discuss our patient's etiology and pathogenesis.

Transfusion management of factor V deficiency: three case reports and review of the literature

BACKGROUND

Factor V (FV) deficiency may be inherited as an autosomal recessive disease or acquired as a result of autoantibody formation, either spontaneously or secondary to exposure to bovine thrombin or medications. Congenital FV deficiency has traditionally been treated with plasma transfusions. However, recent evidence has suggested that platelet (PLT) transfusions may be a better alternative as FV stored within PLT alpha granules has greater procoagulant potential and is released locally at sites of vascular injury. We report three cases of FV deficiency, one congenital and two acquired, and emphasize the different management approaches.

CASE REPORTS

Patient 1 was a 30-year-old man with congenital FV deficiency who presented with a trauma-induced hematoma of his lower extremity. He was treated with 5 PLT units over 48 hours. Patient 2 was a 64-year-old woman who presented with an upper-extremity thrombus and was discovered to have a FV inhibitor, likely secondary to antibiotics. Patient 3 was a 75-year-old woman with hepatitis C virus (HCV) who presented with minor ecchymosis and was found to have a FV inhibitor secondary to either HCV or antibiotic exposure. Corticosteroids alone were able to eradicate the inhibitors in both patients with acquired inhibitors.

CONCLUSIONS

FV deficiency can present with a diverse range of symptoms. For bleeding patients, PLT transfusions should be the initial therapy. In patients with thrombosis, the risks and benefits of anticoagulation must be carefully assessed before treatment. For patients with minor bleeds, transfusions may be withheld, and elimination of the inhibitor should be the primary objective.

Acquired factor V inhibitor after exposure to topical human thrombin related to an otorhinolaryngological procedure

Acquired factor V (FV) inhibitors occur rarely and classically develop after exposure to bovine thrombin. The clinical presentation is variable, ranging from asymptomatic with incidental laboratory abnormalities to significant bleeding. With the development of human-derived thrombin agents, bovine thrombin is less frequently used. We report a case of an acquired FV inhibitor that developed in a patient after exposure to human thrombin used as a hemostatic agent during an otorhinolaryngology surgical procedure. Our review of the literature revealed only one prior reported case of FV inhibitor after exposure to human thrombin. Hematologists and surgeons should be aware of this rare, but potentially life-threatening, complication in the postprocedural setting.

Acquired factor V inhibitor associated with life-threatening bleeding and a mixing test result that indicated coagulation factor deficiency

A mixing test is useful for distinguishing between coagulation factor deficiency and the presence of inhibitor as the cause of coagulopathy. However, we experienced a patient with acquired factor V (FV) inhibitor whose mixing test showed a coagulation factor deficiency pattern. A 65-year-old man with a tendency for bleeding was referred to our center. The laboratory data showed remarkable prolongation of prothrombin time and activated partial thromboplastin time (APTT). FV activity was less than 3%. A mixing test showed a coagulation factor deficiency pattern. However, neither the tendency for bleeding nor the coagulation tests were corrected by transfusion of fresh frozen plasma. A few days later, a positive test for FV inhibitor of 3 Bethesda units was obtained. Therefore, we started prednisolone and plasma exchange, and the coagulation test results normalized after 6 weeks. Although an incubation period is generally not considered necessary in a mixing test for FV inhibitor, we repeated mixing tests with various incubation periods and confirmed an incubation period-dependent prolongation of the APTT. Therefore, a mixing test with an incubation period is recommended for the detection of FV inhibitor, since a mixing test without an incubation period may show a coagulation factor deficiency pattern when the titer of FV inhibitor is low.

Acquired factor V inhibitor developing in a patient with esophageal squamous cell carcinoma

An 82-year-old man referred to our medical ward because of epistaxis and melena was found to have 12 Bethesda units of factor V inhibitor. He was managed for bleeding with supportive care, followed by corticosteroid therapy. The bleeding completely stopped 1 week after corticosteroid therapy. Medical history revealed dysphagia during the past 6 months and further evaluation brought to light a squamous cell carcinoma (SCC) in the esophagus. This is the first case of an acquired factor V inhibitor developing in a patient with esophageal SCC without any other risk factors such as surgery.

Acquired factor V inhibitors: a systematic review

The occurrence of an inhibitor against coagulation factor V (FV) is a rare but challenging condition, which may span from asymptomatic laboratory abnormalities to potentially life-threatening bleeding. The onset of FV inhibitors has been associated most frequently in the past with the patients' exposure to topical bovine thrombin administered during surgery procedures. However, since this preparation is no longer used, in this systematic review we have only focused on non-bovine thrombin-related FV inhibitor cases.

Postoperative paraneoplastic factor VIII auto-antibodies in patients with solid tumours

Paraneoplastic FVIII antibodies may occur concurrent with the diagnosis or at various times after diagnosis and treatment of cancer. Between 2002 and 2009, we observed two patients with acquired haemophilia A due to an FVIII auto-antibody, which appeared 4 and 5 months after uncomplicated cancer surgery. We aimed to evaluate if such an association of cancer surgery and FVIII antibody formation has been observed previously. We retrieved all published case reports of cancer-associated FVIII auto-antibodies from PubMed for the period 1950-2010. The search in the literature revealed 13 patients in whom a FVIII inhibitor developed after uncomplicated surgery for cancer and a bleeding-free time interval of up to 6 months; 11/15 patients had abdominal cancers (five colon cancer, four pancreatic cancer, gastric cancer and choledochus carcinoma one each). The median time period between surgery and antibody detection was 3 months (1 week-6 months). In most cases, the antibody titre was low (median: 14 BU mL⁻¹, range: 1.7-64 BU mL⁻¹). Immunosuppressive treatment was successful in most of the cases - nine of the treated patients reached a sustained CR of the antibody after a median time of 3 months. Postoperative paraneoplastic FVIII inhibitors may be regarded as a special, not yet recognized subgroup of acquired FVIII antibodies. They share some characteristics with postpartum FVIII inhibitors with regard to the latency period between the triggering event and the appearance of the antibody, and between the usually low antibody titres and their good response to immunosuppressive treatment.

Development of cephradine-induced acquired factor V inhibitors: a case report

OBJECTIVE

To report a case of cephalosporin-induced factor V inhibitor development, an uncommon but potentially fatal condition characterized by severe hemorrhage.

CASE SUMMARY

A 71-year-old Chinese man presented with factor V inhibitors after a 7-day cephradine course for a urinary tract infection, characterized by abnormal prothrombin time (PT) and activated partial thromboplastin time (aPTT), gross hematuria, upper gastrointestinal bleeding, and left groin hematoma. Systemic corticosteroid administration restored his factor V activity levels, PT, and aPTT to within normal limits, and hemorrhagic symptoms resolved. Three weeks after successful treatment of bleeding diathesis, he received another 8-day cephradine course for cellulitis. After another 4 weeks, he suffered from recurrent factor V inhibitors presented with abnormal PT, aPTT, and upper gastrointestinal bleeding. The patient eventually died due to hemorrhagic shock despite a second course of corticosteroids.

DISCUSSION

Cephalosporins are known to cause coagulopathy via hypoprothrombinemia. Another pathway seldom mentioned in the literature is factor V inhibitor induction, which may result in factor V deficiency. In our patient, factor V deficiency due to inhibitors developed each time that the patient received repeated cephradine treatment. According to the Naranjo probability scale, the relation between the formation of factor V inhibitors and cephradine treatment was probable.

CONCLUSIONS

Because cephalosporins are commonly used for their wide therapeutic index and few adverse effects, iatrogenic complications associated with these drugs may be neglected or underdiagnosed. On the basis of our patient's report, careful review of medical records to avoid reexposure to the offending drug cannot be overemphasized.

Cross-reactivity of rabbit anti-bovine prothrombin/thrombin IgGs with bovine factor V/Va-related antigens

The purpose of this study was to determine whether rabbit anti-bovine prothrombin/thrombin immunoglobulin Gs (IgGs) would cross-react with bovine factor V/Va-related antigens. Bovine prothrombin, crude thrombin, as well as 2 purified versions of thrombin, that is, thrombin 4A (the previous version of Thrombin-JMI marketed prior to 2008) and 4B (the currently marketed version of Thrombin-JMI), were administrated to individual groups of rabbits on days 0, 21, 42, 91, 123, and 151 using standard immunologic methods. Blood was drawn from each rabbit on days 30, 50, 105, 137, and 165 and the pooled antisera from individual groups were purified to obtain the IgGs using protein G affinity columns. By probing bovine factor V/Va samples, the possible cross-reactivity of each IgG collected at different time points (from day 30 to day 165) was explored using Western blotting techniques. The results indicated that rabbit anti-bovine prothrombin and crude thrombin IgGs could cross-react strongly with bovine factor V/Va in an immunization time-dependent manner. However, antibodies generated in thrombin 4A-treated rabbits presented much weaker cross-reactivity with bovine factor V/Va. Furthermore, no cross-reactivity with bovine factor V/Va-related antigens was observed when the anti-bovine thrombin 4B IgG collected at any time point was used. The results suggest that thrombin 4B preparation contains the least bovine factor V/Va contaminants among the bovine prothrombin/thrombin preparations studied and the amount of bovine factor V/Va contaminants in bovine thrombin 4B is too small to elicit the generation of antibodies against bovine factor V/Va in rabbits.

Comparison of immunogenic potentials of bovine thrombin preparations

Using a membrane filtration step, bovine crude thrombin was purified into thrombin 4A and 4B preparations. The purpose of this study was to determine whether the improved purity of a bovine thrombin preparation can reduce its overall immunogenic potential and lower the risk of development of factor V antibodies. Bovine crude thrombin and its purified versions, thrombin 4A and 4B, were administered to individual groups of rabbits on days 0, 21, 42, 91, 123, and 151 using standard immunologic methods. Blood was drawn from each rabbit on days 30, 50, 105, 137, and 165, and the pooled antisera from individual groups were purified to obtain the Ig Gs using protein G affinity columns. Using Western blotting, the specificity of each immunoglobulin G collected at the first time point (day 30) and last time point (day 165) was determined. The results of Western blotting using the Ig Gs collected on days 30 and 165 were consistent; both demonstrating that thrombin 4B has the least immunogenic potential among the 3 thrombin preparations tested. Compared with the immunoglobulin Gs collected on day 30, the Ig Gs from day 165 did not show obvious difference regarding their ability to detect antigens in bovine thrombin samples. Neither showed cross-reactivity with human coagulation factors nor the recognition of bovine factor Va antigens. These results suggest that despite the presence of a trace amount of bovine factor Va antigen in bovine thrombin preparations, these contaminants failed to elicit the generation of antibodies against factor Va light chain in rabbit.

Successful treatment with rituximab in a patient with an acquired factor V inhibitor

Rituximab has already been successfully used to treat immune-mediated bleeding disorders such as acquired factor VIII inhibitor. We report here a case of severe acquired factor V (FV) inhibitor deficiency due to FV inhibitor which has been dramatically improved after rituximab.

Reduced Immunogenic Potential of Membrane Filtered Bovine Thrombin Preparations for Hemostatic Application

There is concern that exposure to bovine thrombin can result in the development of antibodies, usually against factor V/Va, which can lead to hemostatic abnormalities. It is thought that purer preparations of bovine thrombin might be less immunogenic. Utilizing newer methods including a membrane filtration step, bovine crude thrombin is further purified into thrombin 4A and 4B preparations which exhibit a higher specific activity and are devoid of some of the protein contaminants. Bovine crude thrombin and its purified versions were administered intravenously to individual groups of rabbits using standard immunologic protocols. Antiserum was drawn from each rabbit and the pooled antisera were purified to obtain the IgGs using protein G affinity columns. The results suggest that the reported purification process, including filtration, resulted in the removal of most of the antigens found in crude thrombin, and that none of these preparations generated any detectable antibodies against bovine factor V related antigens.

Factor V inhibitor: case report

Acquired inhibitors to coagulation factors are rare, certainly those directed against factor V. A total of around 150 cases have so far been reported, of which the greater part was due to bovine thrombin exposure. We report the case of a patient who developed a factor V inhibitor during a postoperative period. This report describes possible aetiologies, varying clinical conditions and treatment possibilities as described in the literature. Furthermore, this case report is an example of the often unpredictable disease progression in a patient with existence of a factor V inhibitor.

Acquired factor V inhibitor responsive to corticosteroids in a patient with double cancers

A 70-year-old woman suffering from HCV-related liver cirrhosis was admitted for abnormal bleeding. Laboratory findings included PT at 46.6 sec, APTT at >212 sec, factor V activity of <3%, and factor V inhibitor of 2 BU. Having experienced a persistent bleeding tendency for one month, the patient was started on prednisolone (0.8 mg/kg/day). Within a few days, the inhibitor became undetectable and clinical bleeding disappeared. Although clinical improvement was achieved, she died 6 months after the initial bleeding episode from the progression of a lung cancer. An autopsy revealed squamous cell carcinoma of the lung and hepatocellular carcinoma.

Spectrum of bleeding in acquired factor V inhibitor: a summary of 33 cases

Coagulation factor V (FV) is an essential component of the prothrombinase complex, which activates the zymogen prothrombin to thrombin. Acquired FV inhibitor is rare and clinical symptoms are quite variable. The aim of this study was to summarize the spectrum of the bleeding presentation of acquired FV deficiency and characterize the underlying causes of the clinical symptoms. This study was designed as a descriptive retrospective and 30 case reports were included for further analysis. At least 33 cases of acquired FV inhibitor were investigated. Most patients have a presentation of bleeding and most of those are from hematuria and bleeding at surgical sites. Seven cases of asymptomatic acquired FV inhibitor were also detected. A total of 39.4% (19 of 33) of those cases with acquired FV inhibitor have an unknown cause. For those with known etiologies, chemical and drug-induced causes are the most common (30.8%).