Acquired FV inhibitors: a needless iatrogenic complication of bovine thrombin exposure

Idiopathic factor V inhibitor in a patient starting haemodialysis

A 74-year-old Pacific Island man with end-stage renal failure planning to start haemodialysis presented with persistent bleeding after tunnelled dialysis catheter insertion. The laboratory findings revealed a prolonged activated partial thromboplastin time of 118 s, prothrombin ratio of 4.2, factor V activity of <2% and a factor V inhibitor of 40 Bethesda Units. No clear underlying aetiology was identified. The bleeding settled with conservative measures and the factor V inhibitor was successfully treated with oral cyclophosphamide for 6 weeks.

Clinical Issues-October 2022

Verifying patient identity before blood product administration Key words: patient identification, patient verification, blood transfusion, blood management, wristband. Surgical site infection risk with allogeneic blood administration Key words: patient blood management, restrictive transfusion triggers, allogeneic blood products, intraoperative blood salvage, surgical site infection. Information on topical thrombin Key words: hemostatic agents, licensed biological product, hemostasis, bovine thrombin, human thrombin. Safe use of topical thrombin Key words: severe adverse events, hemostatic agents, accidental injection, accidental intravascular uptake, product labeling.

Immune complications and their management in inherited and acquired bleeding disorders

Disorders of coagulation, resulting in serious risks for bleeding, may be caused by autoantibody formation or by mutations in genes encoding coagulation factors. In the latter case, antidrug antibodies (ADAs) may form against the clotting factor protein drugs used in replacement therapy, as is well documented in the treatment of the X-linked disease hemophilia. Such neutralizing antibodies against factors VIII or IX substantially complicate treatment. Autoantibody formation against factor VIII leads to acquired hemophilia. Although rare, antibody formation may occur in the treatment of other clotting factor deficiencies (eg, against von Willebrand factor [VWF]). The main strategies that have emerged to address these immune responses include (1) clinical immune tolerance induction (ITI) protocols; (2) immune suppression therapies (ISTs); and (3) the development of drugs that can improve hemostasis while bypassing the antibodies against coagulation factors altogether (some of these nonfactor therapies/NFTs are antibody-based, but they are distinct from traditional immunotherapy as they do not target the immune system). Choice of immune or alternative therapy and criteria for selection of a specific regimen for inherited and autoimmune bleeding disorders are explained. ITI serves as an important proof of principle that antigen-specific immune tolerance can be achieved in humans through repeated antigen administration, even in the absence of immune suppression. Finally, novel immunotherapy approaches that are still in the preclinical phase, such as cellular (for instance, regulatory T cell [Treg]) immunotherapies, gene therapy, and oral antigen administration, are discussed.

Advances in the development of hemostatic biomaterials for medical application

BACKGROUND

Medical hemostatic biological materials are necessary for the development of the process of preventing and stopping damaged intravascular bleeding. In the process, some red blood cells and white blood cells are trapped in nets. The resulting plug is called a blood clot. This is often a good step in wound healing, but separation of blood clots from blood vessel walls can cause serious health problems.

MAIN BODY

The advance in the development of hemostatic biomaterials is necessary for biomedical application. Firstly, the historical background of artificial hemostasis has been included and the current research of hemostasis has been included in more detail. Secondly, the current research of hemostasis has been included on the oxidized cellulose-based hemostatic biomaterials such as starch based on composite cross-linking hemostatic networks, hemostatic materials on NHS-esters, hemostatic agent from local materials and biomaterials for hemostatic management. Thirdly, polysaccharide hemostatic materials, bio-inspired adhesive catechol-conjugated chitosan, mesoporous silica and bioactive glasses for improved hemostasis, minimally invasive hemostatic biomaterials and chitosan-base materials for hemostatic application have been included. Fourthly, the biological properties of natural hemostatic agent by plasma technology and the hemostatic agents based on gelatin-microbial transglutaminase mixes have been also included.

CONCLUSION

Current research on hemostasis includes hemostatic biomaterials such as cellulose-based hemostatic starch based on a complex cross-linked hemostatic network. It also includes polysaccharide hemostatic materials, biomimetic adhesive catechol-binding chitosan, mesoporous silica or physiologically active glass for hemostatic improvement, minimally invasive hemostatic chitosan-based materials, and gelatin-microbial transglutaminase-based hemostatic agents. Future studies should focus on modular combination of hemostatic imitation and reinforcement mechanisms of different materials and technologies to find the optimal system to promote and strengthen active platelet or platelet imitation aggregation in bleeding sites. The second optionally increases the production of thrombin and fiber formation at the site. Third, the formed fibrin biopolymer network has strengthened to reduce thrombosis and amplify hemostasis.

Bone regeneration of demineralized dentin matrix with platelet-rich fibrin and recombinant human bone morphogenetic protein-2 on the bone defects in rabbit calvaria

BACKGROUND

This study was to evaluate the bone formation ability of demineralized dentin matrix (DDM) combined with platelet-rich fibrinogen (PRF) and DDM combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) to improve the osteoinductive ability of DDM.

METHODS

After four bone defects with a diameter of 8mm were created in the calvarium of each rabbit, DDM was grafted into the first defect (experimental groups 1), a combination of DDM and PRF was grafted into the second defect (experimental groups 2), and DDM with absorbed rhBMP-2 was grafted into the third defect (experimental groups 3). The fourth defect was used as the control group. Twelve healthy male rabbits (New Zealand, white rabbits) weighing around 3.0-4.0 kg were used. Among 12 rabbits, 3 rabbits were sacrificed immediately after surgery and at 2, 4, and 8 weeks after surgery, respectively. Histopathologic analysis and histomorphometric analysis were conducted to evaluate bone formation in each group.

RESULTS

The PRF/DDM group did not show a significantly higher degree of new bone formation in calvarial bone defects than the DDM group at 2, 4, and 8 weeks postoperatively in histopathological findings and histomorphometric results. On the other side, the rhBMP-2/DDM group showed higher degrees of new bone formation and calcification, and the lamellae of bone matrix, which are observed in mature bone tissue, were more distinctly visible in the rhBMP-2/DDM group. Moreover, the rhBMP-2/DDM group showed a significantly higher amount of new bone formation, compared to the DDM group at 4 and 8 weeks postoperatively (P<0.05) in histomorphometric results.

CONCLUSION

The DDM has great potential as a carrier for the maintenance and sustained release of rhBMP-2, which has been recently receiving wide attention as a type of signaling molecules to promote bone formation.

A rare case of acquired factor V inhibitor, during treatment with dabigatran for chronic atrial fibrillation, successfully treated with bypassing agents

Acquired factor V inhibitor represents a rare condition, described only in case reports. The use of activated bypassing agents in bleeding control could be of aid and improve the survival in symptomatic patients with acquired factor V inhibitor.

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.

Advances in managing rare acquired bleeding disorders

INTRODUCTION

Rare acquired bleeding disorders include a wide spectrum of coagulopathies characterized by spontaneous or post-trauma and post-surgery hemorrhages in patients without a previous personal or family history of bleeding.

AREAS COVERED

This review, based on a Medline/PubMed search during the last 20 years, will focus mainly on rare acquired bleeding disorders caused by autoantibodies against coagulation factors, including autoantibodies against factor VIII (acquired hemophilia A), von Willebrand factor (acquired von Willebrand syndrome) and other coagulation factors (factors V, X, XI, and XIII). The pathogenic, laboratory, and clinical features of these rare hemorrhagic conditions will be discussed, with particular attention to their management.

EXPERT OPINION

The treatment of rare acquired bleeding disorders includes the control of bleeding and the elimination of the autoantibody and of the underlying disease, when present. As the bleeding clinical phenotype is often severe, the management of affected patients is particularly challenging. Thus, while an early diagnosis of the acquired coagulopathy is essential to start the most appropriate treatment and to improve patients' outcomes, the support of specialized centers is equally important to provide a correct management of such complicated cases.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

A Possible Allergic Reaction Case to Thrombin Injected into Pseudoaneurysm After Radiofrequency Ablation

BACKGROUND Radiofrequency ablation is a minimally invasive treatment for arrhythmias, including frequent ventricular premature. As a complication of radiofrequency ablation, pseudoaneurysm can be treated conservatively or by ultrasound-guided thrombin injection. CASE REPORT We report a case that a possible allergic reaction to thrombin injected into pseudoaneurysm after radiofrequency ablation. CONCLUSIONS We hope that the report of successful management of the allergic reaction in this case may be of help to other doctors; we also emphasize the importance of checking the patient's history of allergies to thrombin when considering treating pseudoaneurysm with thrombin injection.

Acquired Factor V Inhibitor with Hemorrhagic Symptoms after Prasugrel Hydrochloride Treatment

Acquired factor V inhibitor (AFVI) is a rare coagulopathy. It may be triggered by specific antigens such as antibiotics. We herein report the first case of AFVI after treatment with prasugrel hydrochloride (prasugrel) in an 80-year-old male who underwent percutaneous coronary intervention because of angina pectoris 6 years ago and was initiated on aspirin and ticlopidine hydrochloride. He was switched from ticlopidine hydrochloride to prasugrel before undergoing percutaneous coronary intervention for myocardial infarction. Fifteen days later, he developed sudden nasal hemorrhage, hematuria, and systemic purpura. Coagulation tests revealed prolonged prothrombin time-international normalized ratio (11.35) and activated partial thromboplastin time (170 s). The coagulation factor profile revealed a decreased FV activity (1%). The Bethesda assay for FV inhibitor was positive. AFVI was diagnosed; prasugrel was immediately discontinued, and administration of recombinant activated factor VII and prednisolone were initiated. Hemorrhagic symptoms immediately disappeared; FV activity improved, and the FV inhibitor titer was normalized.

Severe serous cavity bleeding caused by acquired factor V deficiency associated with lymphatic leakage in a hemodialysis patient: A case report

BACKGROUND

Acquired factor V deficiency is a rare secondary hemorrhagic disease, which can lead to a severe bleeding disorder.

CASE SUMMARY

We report a 47-year-old hemodialysis patient who presented with severe hemorrhagic pleural effusion and hemorrhagic pericardial effusion associated with lymphatic leakage. The laboratory examination revealed decreased factor V activity (2% of population average value). With decreased lymphatic leakage, factor V activity increased (to 46%). Lymph drainage correlated with prothrombin time and active partial thrombin time. The cause of the disease favored an acquired disease. The common causes which trigger factor V inhibitors were excluded. An inhibitor was not detected. It is possible that there was a clotting factor inhibitor leaking with the lymph in the drainage. Inhibitor production may be due to immune dysfunction caused by persistent lymphatic drainage, or that coagulation inhibitors were produced, drained with the lymph, and partly cleared by hemodialysis.

CONCLUSION

In this case, we have firstly reported factor V deficiency associated with lymphatic leakage in a hemodialysis patient.

Evaluation of a Novel Collagen Hemostatic Matrix: Comparison of Two Hemostatic Matrices in a Rabbits Jejunal Artery Injury Model

BACKGROUND

We evaluated the hemostatic efficacy and immunogenicity of CollaStat compared with FloSeal in a rabbit jejunal artery injury model.

METHODS

A total of 27 experimental rabbits were used in the study. For each hemostatic agent, an injury was created in one of the right angles of the jejunal arteries originating from the vascular arcs. Time to hemostasis was determined after applying manual compression to the wound for 30 s, which was repeated a maximum of three times in cases of persistent bleeding. On postoperative day 7, the concentration of serum antithrombin antibody was measured among agent-treated and nontreated control groups.

RESULTS

The mean time to hemostasis for CollaStat was significantly shorter than for FloSeal (64.0 ± 5.0 versus 84.0 ± 7.8 s; P = 0.040). There were no significant differences in rabbit serum mean anti-thrombin Ab concentration between CollaStat-treated, FloSeal -treated, and the control groups (8.43 ± 0.44 versus 8.18 ± 7.8 versus 9.58 ± 1.11 ng/mL; P = 0.065).

CONCLUSIONS

According to our study, CollaStat was more efficient in achieving hemostasis in a rabbit jejunal artery injury and exhibited nonsignificant immunogenicity compared with FloSeal. These findings suggest that CollaStat has acceptable hemostatic potential for controlling significant arterial bleeding.

Cytocompatibility and mechanical properties of surgical sealants for cardiovascular applications

OBJECTIVES

The present study compared physical, mechanical, and biologic characteristics of 4 clinically available surgical sealants for cardiovascular repair.

METHODS

BioGlue (Cryolife Inc, Kennesaw, Ga), PreveLeak (Mallinckrodt Pharmaceuticals, St Louis, Mo), Tridyne VS (BD, Franklin Lakes, NJ), and Coseal (Baxter Healthcare Corporation, Westlake Village, Calif) were compared for the following properties: hydrated swelling, cytocompatibility, burst strength, biaxial stretching (elasticity), and in vitro degradation.

RESULTS

Sealants showed a wide range of swelling upon hydration. By gravimetric and volumetric measurement, swelling was greatest for Coseal followed by Tridyne VS, BioGlue, and PreveLeak. Tridyne VS was the most cytocompatible based on Alamar Blue assay results, supporting 85% cell survival compared with 36% to 39% survival with the other sealants. All sealants withstood pressure above mean arterial pressure (70-110 mm Hg) and physiologic systolic blood pressure (90-140 mm Hg) in an ex vivo arterial flow burst model; lowest peak pressure at failure was PreveLeak at 235 ± 48 mm Hg, and highest peak pressure at failure was BioGlue at 596 ± 72 mm Hg. Biaxial tensile testing showed no differences in elasticity between ex vivo porcine aorta and carotid arteries and Tridyne VS or Coseal, and BioGlue and PreveLeak were significantly stiffer. In vitro degradation time for Coseal was 6 days and 21 days for Tridyne VS. No degradation was observed in BioGlue or PreveLeak for 30 days.

CONCLUSIONS

Although all sealants withstood supraphysiologic arterial pressure, there were differences in characteristics that may be important in clinical outcome. Coseal degradation time was short compared with other sealants, whereas BioGlue and PreveLeak showed a significant compliance mismatch with native porcine carotid artery. Tridyne VS was significantly more cytocompatible than the other 3 sealants.

Antibacterial Activity of Leukocyte- and Platelet-Rich Plasma: An In Vitro Study

The aim of the study was to investigate the leukocyte- and platelet-rich plasma (L-PRP) antimicrobial activity. The studied sample comprised 20 healthy males. The L-PRP gel, liquid L-PRP, and thrombin samples were tested in vitro for their antibacterial properties against selected bacterial strains using the Kirby-Bauer disc diffusion method. Two types of thrombin were used (autologous and bovine). Zones of inhibition produced by L-PRP ranged between 6 and 18 mm in diameter. L-PRP inhibited the growth of Staphylococcus aureus (MRSA and MSSA strains) and was also active against Enterococcus faecalis and Pseudomonas aeruginosa. There was no activity against Escherichia coli and Klebsiella pneumoniae. The statistically significant increase of L-PRP antimicrobial effect was noted with the use of major volume of thrombin as an activator. Additionally, in groups where a bovine thrombin mixture was added to L-PRP the zones of inhibition concerning MRSA, Enterococcus faecalis, and Pseudomonas aeruginosa were larger than in the groups with autologous thrombin. Based on the conducted studies, it can be determined that L-PRP can evoke in vitro antimicrobial effects and might be used to treat selected infections in the clinical field. The major volume of thrombin as an activator increases the strength of the L-PRP antimicrobial effect.

A discrepancy between prothrombin time and Normotest (Hepaplastintest) results is useful for diagnosis of acquired factor V inhibitors

Acquired coagulation factor inhibitors are rare. Among them, coagulation factor V (FV) inhibitor is particularly uncommon and presents with variable clinical manifestations. Certain acquired FV inhibitor patients have only mild bleeding or, in select cases, no symptoms at all, leading to spontaneous recovery. Others have life-threatening bleeding that requires medical attention. Thus, a prompt decision regarding diagnosis and clinical intervention is crucial for such patients. In five acquired FV inhibitor cases treated in our facility, each patient had a malignancy as an underlying disease and all unexpectedly showed prolongation of both prothrombin time (PT) and activated partial thromboplastin time (APTT). They all also displayed a discrepancy between PT and Normotest (Hepaplastintest, HPT) results. All but one patient experienced no bleeding at the time of diagnosis and achieved spontaneous recovery in 1-3 weeks. The patient with bleeding symptoms received plasma exchanges and a platelet transfusion. Useful markers in diagnosing the presence of an acquired FV inhibitor were a sudden prolongation of PT and APTT, and a discrepancy between the PT/APTT and HPT assays. Spontaneous recovery can be expected for patients with only minor bleeding.

A Case of Intraoperative Anaphylaxis Caused by Bovine-Derived Thrombin

Intraoperative bovine-derived topical thrombin is still widely used for hemostasis during surgery. A 38-year-old woman with chronic spontaneous urticaria was referred to the orthopedic surgery department for herniated disk and myelopathy. During the first stage of operation, bovine-derived thrombin powder soaked in Gelfoam was used as a hemostatic aid. After 30 minutes, the patient developed anaphylactic shock with systemic skin rash and angioedema. Repeated intravenous bolus and infusion of vasopressor were carried out, and her blood pressure normalized. Skin test and specific immunoglobulin E test showed positive results for bovine thrombin and beef, respectively. During the second stage of operation (After 10 days from first stage of operation), bovine-derived thrombin powder was excluded and the operation was successful without any unexpected events. Therefore, bovine thrombin should be used with caution because it might cause anaphylaxis.

Factor V Inhibitors: A Diagnostic and Therapeutic Challenge

Historically, inhibitors to coagulation factor V (FV) most often have developed in patients treated with bovine thrombin, a topical hemostatic agent used during surgical procedures. With the advent of newer hemostatic agents, and the concurrent diminished use of bovine thrombin, the incidence of FV inhibitors has fallen. Nevertheless, FV inhibitors are occasionally seen on an idiopathic basis as well as in association with medications, malignancies, autoimmune disorders, pregnancy, and infections. Factor V inhibitors may present with life-threatening bleeding or thrombosis, or they may be discovered incidentally as a coagulation screening test abnormality. Management of patients with FV inhibitors is challenging and consists of control of bleeding and eradication of the inhibitor. In this short overview we review the role of platelet and plasma FV in hemostasis and discuss the unique characteristics, clinical features, diagnosis, treatment, and prognosis associated with FV inhibitors.

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.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice-Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating, and categorizing indications for the evidence-based use of therapeutic apheresis in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the Committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

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.

Fatal hemorrhage due to a spontaneous factor V inhibitor with lupus anticoagulant properties

: Factor V inhibitors are rare and have varied clinical presentations. We report on a 76-year-old female admitted to the hospital for pneumonia and treated with multiple antibiotics. Her baseline prothrombin time was 15.6 s and the activated partial thromboplastin time was 35 s. On admission day 10, she developed arm weakness and brain imaging showed a subdural hematoma. The prothrombin time was now 59.1 s with an activated partial thromboplastin time of more than 160 s and a normal thrombin time. A mixing study did not correct the clotting times and coagulation factor assays showed a nonspecific inhibition pattern. Only factor V activity remained low with serial dilutions, however, and a 70 Bethesda Unit inhibitor was identified. Aggressive supportive care was initiated but the patient succumbed to the effects of the intracranial hemorrhage. Factor V inhibitors may display lupus anticoagulant properties and may cause catastrophic bleeding. Our case illustrates that these inhibitors can arise quickly and supports an association with antibiotics.

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.

Development of acquired factor V inhibitor after treatment with ceftazidime: a case report and review of the literature

We report the case of a 59-year-old Chinese man who showed an asymptomatic coagulation factor V deficiency pattern after second intravenous treatment with ceftazidime. Normal pooled plasma failed to correct the abnormalities in a mixing test, and the presence of factor V inhibitor was confirmed by the Bethesda method. The coagulopathy was not corrected by transfusion of fresh frozen plasma and prothrombin complex concentrate, but rather by treatment with prednisone and withdrawal of dubious drugs. The findings reported here should prompt clinicians to watch for drug-induced coagulation factor deficiency.

Acquired factor v inhibitor developing after treatment with dabigatran etexilate methanesulfonate: a case report and review of the literature

A 90-year-old man presented with subcutaneous ecchymoses. He had been under treatment with dabigatran etexilate methanesulfonate (DEM). Prolonged APTT and decreased PT was developed 2 months after the start of DEM, more prolonged 6 months later. DEM was discontinued, the coagulopathy did not improve. Factor V activity was decreased, along with appearance of coagulation factor V inhibitor (FVI). He did not have antiphospholipid syndrome or malignancy. He was diagnosed as having acquired FVI caused by DEM. Steroid pulse therapy was effective. There have been 74 reported cases of AFVI induced by drug treatment, but none after treatment with DEM.

Acquired factor V inhibitor in a patient with mantle cell lymphoma presenting with hematuria followed by thrombosis: a case report

Acquired factor V inhibitor is a rare hemostatic disorder that presents with hemorrhagic manifestations in the vast majority of patients. Factor V inhibitor may develop through a variety of mechanisms involving development of alloantibodies or autoantibodies specific to Factor V. Autoantibodies, in particular, have been reported in a number of conditions. In this report, we describe a case of acquired factor V inhibitor in a patient with mantle cell lymphoma who presented with hematuria. Seven weeks after diagnosis and successful management, the patient developed deep vein thrombosis in the right lower extremity. The patient’s factor V levels were normalized, and the inhibitor was successfully eradicated using corticosteroids. Here, we discuss this rare disorder, its unusual manifestation, and provide a mini-review of the current literature regarding factor V inhibitors.

Bleeding associated with acquired factor V inhibitor in a patient on warfarin treated successfully with prednisolone

An 85-year-old man on warfarin for atrial fibrillation presented with skin bleeding. International normalised ratio (INR) and activated partial thromboplastin time (APTT) were elevated and did not correct even after warfarin reversal with vitamin K, prothrombin complex concentrate (PCC) and fresh frozen plasma. Mixing coagulation studies with normal plasma suggested the presence of an inhibitor rather than the multiple coagulation factor deficiencies expected with warfarin. Assays of the common-pathway coagulation factors revealed factor V concentration <2% with inhibitor level elevated to 11 Bethesda units. The bleeding resolved following a course of corticosteroids. Coagulation studies and factor V level returned to normal along with resolution of the inhibitor. We report the case of the diagnostic dilemma posed and successful therapy implemented despite the limited evidence-based data being available for the treatment of this rare condition.

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.

A rare case of factor V inhibitor in a patient on amiodarone therapy

Factor V inhibitor is in itself a rare entity. We are reporting a case of an elderly male who presented with symptoms of bleeding and was later found to have developed factor V inhibitors. He had been on amiodarone for atrial fibrillation and developed hemorrhagic manifestations due to factor V inhibitors within a few months of initiating amiodarone therapy. Most of the cases of factor V inhibitors reported in the literature were found to be associated with exposure to bovine coagulation factors. However, in our case there was no evidence of bovine thrombin use during surgery. Furthermore, bovine thrombin-associated factor V inhibitors commonly emerge within 1-2 weeks after exposure during surgery versus several months later in our patient. There was dramatic improvement in the coagulation profile 6 weeks after discontinuation of amiodarone and institution of steroids and cyclophosphamide. We propose the consideration of amiodarone as a contributing agent in inhibitor generation even though a spontaneous development of factor V inhibitor could not be ruled out.

Cross-Reactivity of Various Thrombin Products With Anti-Rabbit Antibodies to Bovine, Human, and Recombinant Thrombin

JMI-thrombin is used as topical hemostatic agent. While earlier clinically available JMI were reported to produce immunologic responses upon repeated exposure, the improved JMI, Recothrom?, and Evithrom? are claimed to be less immunogenic. Recothrom, despite its reduced immunogenic nature, upon repeated administration may result in the generation of antibodies (Abs) and that may cross react with bovine and human thrombin. Therefore, groups of rabbits were challenged repeatedly with Recothrom, Evithrom, and JMI over a 9-month period. Pre-immune blood and antiserum were collected from each rabbit on different time point. To determine their relative cross reactivity, JMI, Recothrom, and Evithrom were evaluated by western blotting using the rabbit IgG fractions. The results suggest that anti-Recothrom Abs cross-react with Evithrom and JMI in a time dependent fashion. Anti-JMI Abs did not cross-react with Recothrom, and Evithrom. Also, anti-Evithrom did not show any cross-reactivity with Recothrom and JMI at any time.

Recombinant human thrombin: safety and immunogenicity in pediatric burn wound excision

BACKGROUND

Previous studies of recombinant human thrombin (rThrombin) enrolled adult and adolescent patients. This phase 4, open-label, single-group study was conducted in pediatric patients undergoing synchronous burn wound excision and skin grafting to provide information regarding the safety and immunogenicity of rThrombin (primary and secondary endpoints) in this population.

METHODS

Topical rThrombin was applied as a hemostatic aid during a surgical procedure (day 1). Adverse events and clinical laboratory abnormalities were recorded during the study. Immunogenicity samples were collected on days 1 and 29 (study end). Study results were summarized with descriptive statistics.

RESULTS

Thirty patients enrolled and 28 completed the study. Mean age was 6.9 years (range, 0.9-17.8 years); 40.0% of patients were girls. Flame and scald were the most common burn types (33.3% each, n = 10/30). Mean graft size was 3.6% total body surface area. Procedural pain (50.0% patients), pruritus (43.3%), and anemia (30.0%) were the most commonly reported adverse events. All adverse events and clinical laboratory abnormalities were considered unrelated to treatment. No patients developed anti-rThrombin product antibodies at day 29.

CONCLUSIONS

In pediatric patients undergoing burn wound excision and skin grafting, rThrombin was well tolerated and did not lead to the formation of anti-rThrombin product antibodies.