Quebec platelet disorder (QPD) is a rare, autosomal-dominant, inherited bleeding disorder that is associated with unique abnormalities in fibrinolysis. Its hallmark features are delayed-onset ...bleeding following hemostatic challenges that responds to fibrinolytic inhibitor therapy and increased expression and storage of the fibrinolytic enzyme urokinase plasminogen activator in platelets, without increased plasma urokinase plasminogen activator or systemic fibrinolysis. The increased urokinase plasminogen activator in QPD platelets is only partially inhibited, and, as a result, there is intraplatelet generation of plasmin, and secondary degradation of many platelet alpha-granule proteins. During clot formation, the urokinase plasminogen activator released by QPD platelets leads to platelet-dependent increased fibrinolysis, and this is postulated to be a major contributor to QPD bleeding. The focus of the present review is to summarize the current state of knowledge on QPD, including the history of this disorder, its clinical and laboratory features, and recommended approaches for its diagnosis and treatment.
When availability and/or affordability of anti-hemophilic factor concentrates are limited, optimal prophylaxis regimens in severe hemophilia A (HA) remain to be determined. In selected situations, ...low-dose daily prophylaxis (LDDP) may be an effective and economical option. The goal of our study was to evaluate if subjects on a LDDP regimen could achieve adherence and good clinical outcome.
Seventeen subjects (age between 15.2 and 28.4) on LDDP suffering from severe/moderate HA were followed prospectively for 2 to 3 years as part of a health-related quality of life (HRQoL) study. Bleeding and treatments data were collected using electronic diaries and validated every three months. The SF-36 questionnaire was administered at the beginning of the study and then every 6 months until the end of the study.
The subjects (mean age 22.0, median 21.9, standard deviation 4.06), were all from a single centre and on LDDP for at least 12 months as part of their routine care before entering the study. Fifteen subjects were prescribed a daily dose of 500 IU factor VIII (FVIII) and 2 subjects received 1000 IU FVIII per day, resulting into a median dose of 7.1 IU/kg/day (ranging from 4 to 13 IU/kg/day) and of 2591 IU/kg/year. Median adherence (the percentage of the prescribed daily dose received) was 84 % (mean 80 %, range 57 % to 94 %) throughout the study. Seventy-six bleeds in the 6 index joints and 51 other types of bleeds were observed throughout the study. The median annualized bleeding rate in joints (ABRjoints) was 0.7 and the median annualized bleeding rate for all bleeds (ABRall) was 1.6. The Physical Component and Mental Component Summary scores of SF-36, and the Hemophilia Joint Health Score were not significantly different over the course of the study (respective medians of 49.8, 52.4 and 16.0 at entry; vs. 52.5, 51.5 and 16.0 upon exit).
This prospective longitudinal study in youth and young adults shows that LDDP may be associated with low ABRs, adequate adherence and HRQoL comparable to previously reported.
Thrombin generation and bleeding in haemophilia A BRUMMEL-ZIEDINS, K. E.; WHELIHAN, M. F.; GISSEL, M. ...
Haemophilia : the official journal of the World Federation of Hemophilia,
September 2009, Letnik:
15, Številka:
5
Journal Article
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Haemophilia A displays phenotypic heterogeneity with respect to clinical severity. The aim of this study was to determine if tissue factor (TF)‐initiated thrombin generation profiles in whole blood ...in the presence of corn trypsin inhibitor (CTI) are predictive of bleeding risk in haemophilia A. We studied factor(F) VIII deficient individuals (11 mild, 4 moderate and 12 severe) with a well‐characterized 5‐year bleeding history that included haemarthrosis, soft tissue haematoma and annual FVIII concentrate usage. This clinical information was used to generate a bleeding score. The bleeding scores (range 0–32) were separated into three groups (bleeding score groupings: 0, 0 and ≤9.6, >9.6), with the higher bleeding tendency having a higher score. Whole blood collected by phlebotomy and contact pathway suppressed by 100 μg mL−1 CTI was stimulated to react by the addition of 5 pm TF. Reactions were quenched at 20 min by inhibitors. Thrombin generation, determined by enzyme‐linked immunosorbent assay for thrombin–antithrombin was evaluated in terms of clot time (CT), maximum level (MaxL) and maximum rate (MaxR) and compared to the bleeding score. Data are shown as the mean±SD. MaxL was significantly different (P < 0.001) between the groups: 504 ± 114, 315 ± 117 and 194 ± 91 nm; with higher thrombin concentrations in the groups with lower bleeding scores. MaxR was higher in the groups with a lower bleeding score; 97 ± 51, 86 ± 60 and 39 ± 16 nm min−1 (P = 0.09). No significant difference was detected in CT among the groups, 5.6 ± 1.3, 4.7 ± 0.7 and 5.6 ± 1.3 min. Our empirical study in CTI‐inhibited whole blood shows that the MaxL of thrombin generation appears to correlate with the bleeding phenotype of haemophilia A.
The Quebec Platelet Disorder (QPD) is an unusual bleeding disorder associated with increased platelet stores of urokinase-type plasminogen activator (u-PA) and proteolysis of platelet alpha-granule ...proteins. The increased u-PA and proteolyzed plasminogen in QPD platelets led us to investigate possible contributions of intracellular plasmin generation to QPD alpha-granule proteolysis. ELISA indicated there were normal amounts of plasminogen and plasmin-alpha(2)-antiplasmin (PAP) complexes in QPD plasmas. Like normal platelets, QPD platelets contained only a small proportion of the blood plasminogen, however, they contained an increased amount of PAP complexes compared to normal platelets (P < 0.005). The quantities of plasminogen stored in platelets were important to induce QPD-like proteolysis of normal alpha-granule proteins by two chain u-PA (tcu-PA) in vitro. Moreover, adding supplemental plasminogen to QPD, but not to control, platelet lysates, triggered further alpha-granule protein proteolysis to forms that comigrated with plasmin degraded proteins. These data suggest the generation of increased but limiting amounts of plasmin within platelets is involved in producing the unique phenotypic changes to alpha-granule proteins in QPD platelets. The QPD is the only known bleeding disorder associated with chronic, intracellular activation of the fibrinolytic cascade.
Platelet function disorders represent a heterogeneous group of bleeding disorders with diverse molecular causes that are frequently associated with platelet dense granule deficiency and/or impaired ...aggregation responses. With the exception of Quebec platelet disorder (QPD), bleeding risks for common platelet disorders have not been estimated. This led us to study a Canadian cohort with uncharacterized platelet function disorders and confirmed abnormalities in validated assays for platelet dense granule deficiency and/or light transmission aggregometry (reduced aggregation with ≥2 agonists). Subjects were assessed using: (i) the International Society for Thrombosis and Haemostasis bleeding assessment tool (ISTH-BAT) to determine scores and categorize symptom severity, and (ii) CHAT-P, a clinical history assessment tool for assessment of platelet disorders that included questions about general health and bleeding symptoms/problems and questions previously used to assess bleeding risks for QPD. CHAT-P was completed by subjects (or parent in the case of young children) before review by a hematologist. Participants included: 29 individuals with confirmed platelet function disorders of unknown cause (from 7 families, 10 "sporadic" cases), 12 unaffected relatives and 60 general population controls. A one-way ANOVA was used to compare the overall ISTH-BAT scores between the affected individuals, unaffected relatives and healthy controls. Bleeding risks were estimated as odds ratio (OR) with 95% confidence intervals (CI) using CHAT-P data for general population controls as the comparison group. The total number of affected subjects reporting a bleeding problem/symptom from the group of affected individuals was added up and compared with the corresponding numbers of responses for general population controls and unaffected relatives using ANOVA. Summative bleeding scores for CHAT-P items with OR>1 were used to compare the number and range of abnormal bleeding symptoms experienced by subjects. Individuals with confirmed platelet abnormalities had higher ISTH-BAT scores (median: 9, range: 0-18) than unaffected family members (median: 0, range: 0-1) and general population controls (median: 0, range: 0-6) (p < 0.01), and their most severe symptom scores were for: epistaxis, cutaneous bleeding, menorrhagia, bleeding from dental extractions, surgery and a subdural hematoma at birth. Affected individuals had higher risks for bleeding (OR, 95% CI, p value) including: bleeding from minor cuts/wounds lasting >1 hour (56, 3.1-1000, p<0.01); abnormal bruising (15-65, 1.8-140 to 3.7-1200, p<0.01); prolonged nosebleeds (23, 5.9-92, p<0.01) and nosebleeds requiring medical attention (40, 1.5-520, p<0.01), packing (33, 1.8-620, p<0.01) or cautery (27, 1.5-510, p<0.01); wound healing problems (13, 3.4-53, p<0.01); excessive bleeding from injuries/trauma (9.5, 1-87, p=0.03), oral/dental challenges (44, 5.3-370, p<0.01) and surgery (17, 4.1-68, p<0.01). Affected females reported: bleeding interfering with their sex life (6.5, 1.1-38, p=0.04); menses >7 days (11, 2.5-49, p<0.01); flooding/gushing accidents (3.8, 1.2-12, p=0.04 ) and/or clots with menses (13, 2.6-63, p<0.01); menses requiring treatment (7.8, 2.1-29, p<0.01); and excessive bleeding during childbirth (17, 2.7-105, p<0.01), sometimes requiring surgical intervention (41, 2-810, p<0.01). Affected individuals reported more of these bleeding symptoms (median: 15, range: 0-24) than unaffected family members (median: 2, range: 0-6; p<0.01) and general population controls (median: 1, range: 0-14, p<0.01), although there was overlap. Our study illustrates that uncharacterized platelet function disorders are associated with significantly increased bleeding risks and mild rather than severe bleeding problems. It will be important to translate our study findings for patients and healthcare providers to promote evidence-based care of individuals with confirmed dense granule deficiency and/or impaired aggregation responses, which are common amongst individuals tested for bleeding problems.
No relevant conflicts of interest to declare.
Amniotic fluid embolism is a potentially fatal complication of pregnancy; although several hypotheses have been formulated, the pathophysiology of this condition is not well known. An exaggerated ...release of bradykinin, which is activated by products of the amniotic fluid that enter the maternal circulation, could explain the symptoms that are present in amniotic fluid embolism. The objective of this study was to assess whether bradykinin is involved in amniotic fluid embolism.
The plasma bradykinin–generating capacity was measured serially in a patient who experienced amniotic fluid embolism.
The plasma bradykinin–generating capacity was found to be very low at the time of the initial clinical manifestations, which were characterized by severe hypotension, cardiorespiratory arrest, and coagulopathy.
This study suggests a potential role for bradykinin release in the pathophysiology of amniotic fluid embolism.
Product-dependent anti-factor VIII antibodies Butenas, S.; Krudysz-Amblo, J.; Rivard, G. E. ...
Haemophilia : the official journal of the World Federation of Hemophilia,
July 2013, Letnik:
19, Številka:
4
Journal Article
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Summary
The development of anti‐factor (F)VIII antibodies in haemophilia A (HA) subjects undergoing replacement therapy has been well documented. The correlation between antibody development and the ...FVIII product used for replacement therapy remains a subject of discussion. The aim of this study was to evaluate the presence of anti‐FVIII antibodies towards three commercial rFVIII products in 34 HA subjects’ plasmas. Antibodies were quantitated by a Multiplex Fluorescence Immunoassay. All plasmas contained anti‐FVIII antibodies at variable concentrations ranging from 50 nm to 570 μm. Eleven of the 20 HA subjects treated with one (r)FVIII product contained inhibitory anti‐FVIII antibodies (0.8‐3584 BU). The inhibitory antibody titre and the molar concentrations of total antibody were mildly correlated (r2 = 0.6). Pronounced differences in antibody recognition with the three rFVIII products were observed. For the group treated with Product ‘A’, the titre towards this product was 2.4‐fold higher than that observed with another full‐length rFVIII‐containing product (Product ‘B’) and almost four‐fold higher than that measured with a B domain‐less rFVIII product (Product ‘C’). For the group of 14 HA subjects treated with FVIII other than Product ‘A’, only one showed higher antibody titre when measured with this product. Our data suggest that the development of anti‐FVIII antibodies is biased towards the product used for treatment and that a significant fraction of antibodies bind to the B domain of FVIII.
BACKGROUND: Acquired hemophilia A (AHA) results from auto-antibodies that neutralize factor VIII (FVIII) coagulant function. AHA is rare, usually occurring late in life, and occasionally post-partum. ...It is most often idiopathic, but can be associated with malignancy, autoimmunity, or drugs. In contrast to congenital hemophilia, AHA generally manifests as mucocutaneous bleeding, with poor correlation to antibody titer or residual FVIII activity. Management goals are the achievement of hemostasis and antibody eradication. Here we describe an unusual case of AHA and concomitant factor XIII consumption in a young nulliparous woman.
CASE REPORT: A 24-year-old woman with a symptomatic congenital choledochal cyst underwent a Roux-en-Y bypass, bile duct resection and cholecystectomy. Abdominal sepsis ensued from extended spectrum beta-lactamase Klebsiella, with ertapenem initiation on post-operative day (POD) 5. On POD6 she developed severe intra-abdominal bleeding associated with prolongation of the activated partial thromboplastin time (aPTT) from 35 seconds (pre-operative) to 40 seconds (reference interval 28-35 seconds). On POD10, FVIII activity and FVIII inhibitor titer, using the modified Nijmegen Bethesda assay, were measured at 0.08 U/ml and 4.5 BU/ml, respectively. In addition to supportive transfusion therapy, the patient received a sequence of desmopressin (0.3 mcg/kg IV), recombinant FVIII (50 U/kg), and activated prothrombin complex concentrate (aPCC) (50-75 U/kg IV q8h) with tranexamic acid (10-20 mg/kg IV q8h) from POD13-20. Prednisone was concomitantly initiated (1.5 mg/kg/day) (Figure 1). Bleeding persisted despite reduction in clotting time on rotational thromboelastometry post-aPCC. As neither intensified aPCC nor recombinant factor VIIa (rFVIIa) (80 mcg/kg IV q2h) provided substantial benefit, recombinant porcine factor VIII (rpFVIII) was administered from POD20-28 (100 U/kg IV qd). RpFVIII resulted in hemostatic improvement until anti-porcine FVIII antibodies developed on POD27. On POD28, she was transferred to the local hemophilia treatment center where complete factor analysis identified concurrent FXIII deficiency 0.08 U/ml using a latex immunoassay. FXIII inhibitor analysis using a chromogenic assay was negative. The peak FVIII inhibitor titer and nadir FVIII activity were 74 BU/ml and <0.01 U/ml, respectively. APCC was resumed POD28-37 and plasma derived factor XIII (pdFXIII) was given every 4 days to maintain FXIII >0.20 U/ml. The patient was also treated with rituximab POD28,36,43,50. On POD37, massive intra-abdominal bleeding prompted sequential aPCC, rFVIIa and pd von Willebrand factor (VWF):FVIII concentrate. Once the FVIII inhibitor titer began to wane, bypassing therapy was discontinued and she was managed solely with pdVWF:FVIII. On POD47 all FVIII-related support was discontinued, as the FVIII inhibitor was undetectable and endogenous FVIII normalized. Her FXIII consumption and requirement for FXIII replacement, however, persisted.
DISCUSSION: The unusual features of this case of AHA include the patient's young age, the possible triggers for the FVIII inhibitor (extensive abdominal surgery, sepsis, and/or carbapenem use), and concomitant FXIII deficiency. We hypothesize that FXIII deficiency was secondary to consumption from the massive abdominal wound given its persistence despite normalization of hepatic function. Repeated life-threatening bleeding required trials of multiple hemostatic agents. Persistent and prolonged bleeding despite ongoing FVIII replacement should trigger investigation for a concomitant hemostatic deficiency. AHA is a rare condition, and treatment requires intensive monitoring, clinical experience and specialized laboratory support. Current guidelines are largely derived from expert opinion, and contemporary case descriptions for rare disorders are essential to advance options in best care.
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St. Louis:Baxter/Baxalta: Consultancy. Sholzberg:CSL Behring: Honoraria, Research Funding; Baxalta: Honoraria, Research Funding; Amgen: Honoraria.
Haemophilia A individuals displaying a similar genetic defect have heterogeneous clinical phenotypes. Our objective was to evaluate the underlying effect of exogenous factor (f)VIII on tissue factor ...(Tf)‐initiated blood coagulation in severe haemophilia utilizing both empirical and computational models. We investigated twenty‐five clinically severe haemophilia A patients. All individuals were on fVIII prophylaxis and had not received fVIII from 0.25 to 4 days prior to phlebotomy. Coagulation was initiated by the addition of Tf to contact‐pathway inhibited whole blood ± an anti‐fVIII antibody. Aliquots were quenched over 20 min and analyzed for thrombin generation and fibrin formation. Coagulation factor levels were obtained and used to computationally predict thrombin generation with fVIII set to either zero or its value at the time of the draw. As a result of prophylactic fVIII, at the time of the blood draw, the individuals had fVIII levels that ranged from <1% to 22%. Thrombin generation (maximum level and rate) in both empirical and computational systems increased as the level of fVIII increased. FXIII activation rates also increased as the fVIII level increased. Upon suppression of fVIII, thrombin generation became comparable in both systems. Plasma composition analysis showed a negative correlation between bleeding history and computational thrombin generation in the absence of fVIII. Residual prophylactic fVIII directly causes an increase in thrombin generation and fibrin cross‐linking in individuals with clinically severe haemophilia A. The combination of each individual’s coagulation factors (outside of fVIII) determine each individual’s baseline thrombin potential and may affect bleeding risk.
Tissue factor (TF) is the most important trigger of blood coagulation in vascular pathology. Rabbit TF, with or without (delta C) its COOH-terminal intracellular tail, has been conjugated to green ...fluorescent protein (GFP) to study subcellular localization and other functions of TF. TF-GFP and TF delta C-GFP are associated with Na2CO3-resistant buoyant fractions in HEK-293 cells (lipid rafts); there is no morphological difference in the surface distribution of these or other GFP-labeled membrane proteins present in or excluded from rafts (confocal microscopy, HEK-293 cells). Endogenous TF expressed by rabbit aortic smooth muscle cells (SMCs) is also raft associated. Membranes from HEK-293 cells expressing recombinant TF-GFP or wild-type TF were equipotent to clot human plasma; however, TF delta C-GFP was approximately 20-fold more active (per membrane weight). Immunoblot confirmed that the deletion mutant is more abundantly expressed, and confocal microscopy showed that it has preferential membrane localization, whereas TF-GFP is mainly intracellular (nuclear lining and multiple granules). With a similar half-life (<4 h), the two constructions differ by their intracellular retention, lower for TF delta C-GFP. In serum-starved SMCs, the expression of endogenous TF was upregulated by interleukin-1 beta and/or FBS treatment (immunoblot, immunofluorescence, clotting assay). However, TF secretion or surface expression was not regulated by stimuli of physiological intensity (such as stimulation of the coexpressed kinin B1 receptors), although a calcium ionophore was highly active in this respect. TF is a raft-associated molecule whose surface expression (secretion) is apparently retarded or impaired by structural determinant(s) located in its COOH-terminal tail.
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