Expanding the Mutation Spectrum Affecting αIIbß3 Integrin in Glanzmann Thrombasthenia: Screening of the ITGA2B and ITGB3 Genes in a Large International Cohort.

We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative defects of the αIIbß3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real-time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual αIIbß3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent αIIbß3 expression; included was a heterozygous c.1440-13_c.1440-1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in αIIb and ß3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin.

Detection and characterisation of large SERPINC1 deletions in type I inherited antithrombin deficiency.

Methods routinely used for investigating the molecular basis of antithrombin (AT) deficiency do not detect large SERPINC1 rearrangements. Between 2000 and 2008, 86 probands suspected of having AT-inherited type I deficiency were screened for SERPINC1 mutations in our laboratory. Mutations causally linked to the deficiency were identified by sequencing analysis in 63 probands. We present here results of multiplex ligation-dependent probe amplification (MLPA) analysis performed in 22 of the 23 remaining probands, in whom sequencing had revealed no mutation. Large deletions, present at the heterozygous state, were detected in 10 patients: whole gene deletions in 5 and partial deletions removing either exon 6 (n = 2), exons 1-2 (n = 1) or exons 5-7 (n = 2) in 5 others. Exon 6 partial deletions are a 2,769-bp deletion and a 1,892-bp deletion associated with a 10-bp insertion, both having 5' and/or 3' breakpoints located within Alu repeat elements. In addition, we identified the 5' breakpoint of a previously reported deletion of exons 1-2 within an extragenic Alu repeat. Distinct mutational mechanisms explaining these Alu sequence-related deletions are proposed. Overall, in this series, large deletions detected by MLPA explain almost half of otherwise unexplained type I AT-inherited deficiency cases.

A case of afibrinogenemia associated with A-alpha chain gene compound heterozygosity (HUMFIBRA c.[4110delA]+[3200+1G>T]).

The clinical features and molecular biology data of a case of afibrinogenemia are reported. The propositus is a 14-year-old girl who suffered several bleeding manifestations that were successfully treated with fibrinogen infusion. The afibrinogenemia results from compound heterozygosity for two mutations on the Aalpha chain gene (c.[4110delA]+[3200+1G>T]). The first mutation is a novel frameshift mutation inherited from her father. The second is a previously described Aalpha chain gene splice junction mutation inherited from her mother. Neither of the parents fulfills the criteria for hypofibrinogenemia.

A novel platelet-type von Willebrand disease mutation (GP1BA p.Met255Ile) associated with type 2B "Malmö/New York" von Willebrand disease.

Interaction between von Willebrand factor (VWF) and platelet GPIbα is required for primary haemostasis. Lack or loss-of-function in the ligand-receptor pair results in bleeding complications. Paradoxically, gain-of-function mutations in VWF or GPIbα also result in bleeding complications as observed in type 2B von Willebrand disease (VWD) and platelet-type- (PT-) VWD, respectively. A similar phenotype is observed with increased ristocetin-induced platelet agglutination and disappearance of the highest molecular weight multimers of VWF. We evaluated a patient with a bleeding disorder and a biological presentation compatible with type 2B VWD. VWF and platelet functional assays, sequencing of the VWF and GP1BA genes, and expression studies in HEK cells were performed. Sequencing of the VWF gene in the propositus revealed a heterozygous p.Pro1266Leu mutation previously found in type 2B VWD Malmö/New York. These variants are characterised by a mild phenotype and a normal VWF multimer composition suggesting the presence of a second mutation in our propositus. Sequencing of the GP1BA gene revealed a heterozygous c.765G>A substitution changing Met at position 255 of GPIbα to Ile. This new mutation is located in the ß-switch domain where five other gain-of-function mutations have been reported in PT-VWD. Expression of GPIbα Ile255 in HEK GPIb-IX cells resulted in enhanced VWF binding compared to wild-type, similar to known PT-VWD mutations (p.Val249, p.Ser249 and p.Val255) indicating that it contributes to the propositus defects. This first report associating PT- with type 2B VWD illustrates the importance of combining biological assays with genetic testing to better understand the clinical phenotype.

A Laboratory Phenotype/Genotype Correlation of 1167 French Patients From 670 Families With von Willebrand Disease: A New Epidemiologic Picture.

von Willebrand disease (VWD) is a genetic bleeding disease due to a defect of von Willebrand factor (VWF), a glycoprotein crucial for platelet adhesion to the subendothelium after vascular injury. VWD include quantitative defects of VWF, either partial (type 1 with VWF levels <50 IU/dL) or virtually total (type 3 with undetectable VWF levels) and also qualitative defects of VWF (type 2 variants with discrepant antigenic and functional VWF levels). The most bleeding forms of VWD usually do not concern type 1 patients with the mildest VWF defects (VWF levels between 30 and 50 IU/dL). The French reference center for VWD performed a laboratory phenotypic and genotypic analysis in 1167 VWD patients (670 families) selected by their basic biologic phenotype: type 3, type 2, and type 1 with VWF levels <30 IU/dL. In these patients indeed, to achieve an accurate diagnosis of VWD type and subtype is crucial for the management (treatment and genetic counseling). A phenotype/genotype correlation was present in 99.3% of cases; 323 distinct VWF sequence variations (58% of novel) were identified (missense 67% versus truncating 33%). The distribution of VWD types was: 25% of type 1, 8% of type 3, 66% of type 2 (2A: 18%, 2B: 17%, 2M: 19%, 2N: 12%), and 1% of undetermined type. Type 1 VWD was related either to a defective synthesis/secretion or to an accelerated clearance of VWF. In type 3 VWD, bi-allelic mutations of VWF were found in almost all patients. In type 2A, the most frequent mechanism was a hyper-proteolysis of VWF. Type 2B showed 85% of patients with deleterious mutations (distinct from type 2B New York). Type 2M was linked to a defective binding of VWF to platelet glycoprotein Ib or to collagen. Type 2N VWD included almost half type 2N/3. This biologic study emphasizes the complex mechanisms for both quantitative and qualitative VWF defects in VWD. In addition, this study provides a new epidemiologic picture of the most bleeding forms of VWD in which qualitative defects are predominant.

Injection of recombinant activated factor VII can induce transient increase in circulating procoagulant microparticles.

Recombinant activated factor VII (rFVIIa) is an effective haemostatic treatment in haemophiliacs with inhibitors. In vitro, FVIIa concentrations corresponding to those obtained with therapeutic doses of rFVIIa have been shown to induce normal thrombin generation and platelet activation in the absence of factors VIII or IX. To further study the in vivo haemostatic changes induced by rFVIIa, circulating procoagulant microparticles (MP) were measured in patients treated with discontinuous injections of Novoseven. In 6 out of 15 patients, a transient peak of procoagulant MP was observed after injection, occurring 15 min to 2 h after infusion. It was composed primarily of platelet-derived MP and was of very short duration. This peak was not observed in haemophiliacs without inhibitor, who were treated with conventional replacement therapies. Our results provide further in vivo evidence that rFVIIa specifically activates platelets, either directly or as a consequence of a burst of thrombin generation that could account for its haemostatic efficacy.

Standardization of factor VII/activated factor VII measurement in plasma of patients treated with recombinant factor activated VII.

To improve the standardization of the factor VII clotting activity (FVII:C) assay in patients treated with recombinant activated factor VII (rFVIIa), we conducted a multicentre study on plasma samples from four patients with haemophilia A, before and at various times after injection of a single dose of rFVIIa. FVII:C and prothrombin time were measured with the methods and reagents routinely used in each laboratory. Strong inter-laboratory variability of FVII:C values was found. The main source of variability was the type of thromboplastin. FVII:C values measured using rabbit thromboplastin were very close to activated factor VII clotting activity values (FVIIa:C) measured with a commercial assay (Staclot VIIa-TF). FVII:C values obtained with human placental thromboplastin were about three times lower than those obtained with rabbit and recombinant thromboplastins, and with the FVIIa:C assay. There was a good relationship between FVIIa:C and activated factor VII antigen values measured using a commercial immunoassay (Imubind FVIIa ELISA). In conclusion, rFVIIa at pharmacological concentrations can be easily monitored on the basis of FVII:C, using rabbit and probably also recombinant thromboplastin; equivalent results are obtained with a specific activated factor VII bioassay.

Fibrinogen Poissy II (gammaN361K): a novel dysfibrinogenemia associated with defective polymerization and peptide B release.

A fibrinogen variant was identified in a pregnant patient with disseminated intravascular coagulation and abruptio placentae. This dysfibrinogen was also found in four asymptomatic members of the patient's family. Coagulation studies showed prolongation of both the thrombin and reptilase times, and discrepancy was noted between the levels of plasma fibrinogen as determined by a kinetic versus an immunological determination or light-scattering assay. Studies on purified fibrinogen revealed an impaired release of fibrinopeptide B by thrombin related to a delayed thrombin-induced fibrin polymerization. DNA sequencing revealed a heterozygous T <-- A point mutation in position 9373 of the gamma-chain gene (exon 9), which substituted a K for an N at position 361.

Underestimation of unfractionated heparin therapy assessment due to platelet activation when using partial-draw (pediatric) citrate collection tubes.

The "so-called" pediatric tubes are often used when collecting smaller blood volume is necessary, particularly in pediatric patients or in case of difficult/recurrent sampling. The aim of this multicenter study was to compare coagulation test results evaluated in evacuated polymer tubes containing 0.109 M citrate (1 vol./9 vol.) specifically designed to allow either a partial (2.0 mL,"pediatric") or a total (3.5 mL) filling. No significantly relevant discrepancy was found between routine coagulation test results in both tubes collected from untreated patients and from patients on vitamin K antagonist or low molecular weight heparin. In contrast, aPTT was significantly shorter and anti-FXa activity was significantly lower in partial-draw than in full-draw tubes collected from 46 patients receiving unfractionated heparin (UFH). This discrepancy was likely related to increased platelet activation in partial-draw tubes, as suggested by higher platelet factor 4 plasma concentrations and platelet P-Selectin expression in partial-draw than in full-draw citrate tubes. To confirm this hypothesis, we then evaluated partial-draw tubes containing CTAD, a mixture of anticoagulant and antiplatelet agents. In 25 patients on UFH, aPTT and anti-FXa activity were not significantly different in partial-draw CTAD tubes and in full-draw citrate tubes. In conclusion, despite increased platelet activation, samples collected into partial-draw citrate tubes allow accurate routine coagulation testing in all patients but those requiring UFH assessment, in which their use could lead to significant underestimation of anticoagulation. In such cases, partial-draw tubes containing CTAD could be validly used to monitor heparin therapy as well as to perform routine coagulation testing.

Risk factors for thrombosis in an african population.

SUMMARY: Little is known about the biological, epidemiological, and clinical risk factors for thrombosis and venous thromboembolism (VTE) among Black Africans. We undertook a study of the prevalence of VTE risk factors for thrombosis in a Senegalese population. A three-year cross-sectional and case-control study involving 105 cases and 200 controls was conducted in various hospitals in Dakar (Senegal). Our results demonstrate that oral contraception, immobilization by casts, surgery, and blood group were significantly associated with VTE occurrence. Additionally, 16 cases and 2 controls had protein S (PS) values of less than 48.4% (M-2SD), exhibiting a highly significant difference (P < 1 × 10(-4)). The number of cases with a low protein C (PC) level was significantly higher than the respective number of controls. Using logistic regression methods, we established a correlation between significantly associated variables and deep venous thrombosis (DVT) occurrence. Age, obesity, sickle cell disease, and PC deficiency were not significantly associated with thrombosis. In contrast, gender, PS deficiency, varicose veins, surgery, non-O blood type, and the presence of antiphospholipid antibodies were significantly and independently associated with DVT. These findings are extremely useful for clinical management of patients suffering from DVT and can help to reduce the high recurrence rate observed in our study.

Hematological disorders related cerebral infarctions are mostly multifocal.

Hematological disorders (HD) have been estimated to implicate approximately 1% of patients with arterial ischemic stroke. However, previously published studies are mostly retrospective or based on case reports or small series in selected young patients. We herein prospectively included consecutive patients with MRI-confirmed cerebral arterial infarctions among individuals admitted in our stroke unit during a 32 month period to determine the clinical and neuroradiological features of ischemic stroke due to HD. Patients with both HD and other identified sources of stroke were excluded. Among patients who were admitted for suspected stroke, 590 had diffusion-weighted MRI confirmed acute arterial infarcts. Cause of the cerebral infarction was HD in 13 patients (2.2%): myeloproliferative disorders (n=4), multiple myeloma (1), lymphoma (1), chronic lymphocytic leukemia (1), disseminated intravascular coagulation (2), thrombotic thrombocytopenic purpura (1), antiphospholipid antibody syndrome (2) and homozygous Q506 factor V mutation associated with lupus anticoagulant (1). The HD were previously known in 6 patients. The only significant difference between the groups of patients with or without HD was the prevalence of multiple acute infarcts in different vascular territories, detected in 53.8% of patients with HD versus 7.8% of patients without HD (mostly due to atherosclerosis, small vessel disease or cardioembolism) (p<0.0001; Fisher exact test). Initial treatment in stroke unit included anticoagulation, steroids, chemotherapy, phlebotomy or plasmatic exchanges, according to etiology. Rankin score at six months was ≤2 in 8 patients. A large spectrum of hematological diseases can be associated with cerebral infarction. In the etiologic work up, HD should be particularly looked for in patients with multifocal acute infarcts to adapt specific therapeutic management.

Thromboxane synthase mutations in an increased bone density disorder (Ghosal syndrome).

Studying consanguineous families with Ghosal hematodiaphyseal dysplasia syndrome (GHDD), a disorder of increased bone density, we identified mutations in TBXAS1, which encodes thromboxane synthase (TXAS). TXAS, an enzyme of the arachidonic acid cascade, produces thromboxane A(2) (TXA(2)). Platelets from subjects with GHDD showed a specific deficit in arachidonic acid-produced aggregation. We also found that TXAS and TXA(2) modulated expression of TNFSF11 and TNFRSF11B (encoding RANKL and osteoprotegerin (OPG), respectively) in primary cultured osteoblasts.

Detection of 28 novel mutations in the Wiskott-Aldrich syndrome and X-linked thrombocytopenia based on multiplex PCR.

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder including microthrombocytopenia, eczema and immunodeficiency. A mild form is known as the X-linked thrombocytopenia (XLT). We screened 150 individuals or families based on a multiplex PCR method. We found 28 novel mutations (7 missense, 1 nonsense, 1 nonstop change, 5 splice site mutations and 14 deletions or insertions). The method relied on the co-synthesis of 5 amplicons and direct sequencing, optimizing the novel protocol proposed by Jones et al. [L.N. Jones, M.I. Lutskiy, J. Cooley, et al. A novel protocol to identify mutations in patients with Wiskott-Aldrich syndrome, Blood Cells Mol. Dis. 28 (2002) 392-398]. It was thus possible to identify faster and at a lower cost the mutations in newly diagnosed patients. The mutation distribution, according to the type, was in keeping with the distribution reported previously. No clear-cut genotype-phenotype correlation was observed.

Circulating microparticles are elevated in haemophiliacs and non-haemophilic individuals aged <18 years.

Platelet and cell stimulation lead to plasma membrane remodelling, resulting in phosphatidylserine (PS) externalisation in the outer leaflet of the membrane, associated with the shedding of PS-rich microparticles (MPs), and contributes to thrombin generation by promoting the assembly of coagulation enzyme complexes. A previous study assessed MP levels in haemophiliacs after haemostatic treatment. To further investigate in vivo membrane remodelling, MP levels and characteristics were studied in 79 haemophiliacs and in 62 non-haemophiliacs. Both groups showed heterogeneity in MP levels, with higher values in individuals <18 years. This finding should be considered when studying MP levels in individuals <18 years.

Efficacy of mycophenolate mofetil in adult refractory auto-immune cytopenias: a single center preliminary study.

UNLABELLED: Treatment of auto-immune cytopenia refractory to front line therapy with intravenous immunoglobulins and steroids is a matter of concern. We assessed the efficacy and safety of mycophenolate mofetil in a prospective open preliminary study. STUDY DESIGN: Adult patients with steroid refractory auto-immune cytopenias were included. Mycophenolate mofetil (MMF) was added to treatment given at the time of inclusion, and efficacy was evaluated in term of improvement of platelet/haemoglobin levels and in term of reduction of previously given drugs, if any. All auto-immune thrombocytopenic purpura (AITP) patients had serologic assessment for associated auto-antibodies at the time of inclusion. Cytopenias associated with other auto-immune diseases, lymphoproliferative diseases or HIV infection were excluded. RESULTS: From November 1999 through November 2003, 13 patients were included (nine AITP, three auto-immune haemolytic anaemia (AIHA), one Evans' syndrome; four males, nine females; age: 35-72 yr). For AITP patients, an overall response of 78% was observed. Retrospective analysis showed no significant difference between patients having a short disease duration (<1 yr) and longer disease duration; between patients who previously received more or less than three treatments; and between patients for whom MMF was started as monotherapy or in association with prednisone, However, all AITP patients presenting associated auto-antibodies responded to MMF, while only 50% of patients without associated antibodies were responders. All patients presenting AIHA and Evans' syndrome were responders. The drug was well tolerated, with no significant side effects reported. The cumulative data suggest a potential place for MMF in the treatment arsenal of refractory cytopenias.