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ABSTRACT: PURPOSE OF REVIEW: Disorders of hemostasis such as hemophilia, von Willebrand disease (VWD), and other clotting protein deficiencies lead to significant morbidity in the pediatric population. Because of the limitations of current treatment options, novel therapies are being developed, many of which are reviewed here. RECENT FINDINGS: Several new observations about the nature of clotting protein physiology have been made recently, creating novel perspectives on the treatment options. This review will mostly focus on the current therapy as well as new progress in hemophilia care (particularly strategies to prolong half-life of clotting factor replacements, the management of inhibitors, gene therapy, and novel therapeutic approaches), and briefly mention some progress in VWD and fibrinogen deficiency therapies. SUMMARY: New therapeutic developments have the potential to dramatically decrease morbidity and improve the quality of life of children with bleeding disorders.
Current opinion in pediatrics 12/2012; · 2.01 Impact Factor
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Pediatric Blood & Cancer 03/2012; · 1.89 Impact Factor
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ABSTRACT: Over the last two decades the genetic causes of several Mendelian platelet disorders have been elucidated, while the genetics of many other thrombocytopenic conditions are still unresolved. Among those are the gray platelet syndrome (GPS) and the thrombocytopenia linked to the THC2 locus on human chromosome 10p11-12. GPS is an α-granule defect associated with the development of myelofibrosis and mild to moderate thrombocytopenia. Most forms of GPS are autosomal recessive, and recently, the recessive form of the disease was mapped to chromosome 3p21. THC2-linked thrombocytopenia is an autosomal dominant disorder in which affected family members have a mild reduction in platelet counts and occasional bleeding. Platelets in THC2-linked thrombocytopenia appear to be normal in size and function although bone marrow morphology reveals a lack of mature, polyploid megakaryocytes. To date, mutations in three different genes within the THC2 locus have been associated with congenital thrombocytopenia, including a mutation in MASTL. In this article, we summarize the recent discoveries in these two forms of thrombocytopenia, including the functional data that support a role for MASTL kinase in thrombopoiesis.
Seminars in Thrombosis and Hemostasis 09/2011; 37(6):690-7. · 4.52 Impact Factor
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Pediatric Blood & Cancer 06/2011; 56(6):974. · 1.89 Impact Factor
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Shay Fabbro,
Walter H A Kahr,
Jesse Hinckley,
Kai Wang,
Jack Moseley,
Gi-Yung Ryu,
Brie Nixon,
James G White,
Thomas Bair,
Brian Schutte, Jorge Di Paola
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ABSTRACT: Gray platelet syndrome (GPS) is an inherited bleeding disorder characterized by thrombocytopenia and the absence of α-granules in platelets. Patients with GPS present with mild to moderate bleeding and many develop myelofibrosis. The genetic cause of GPS is unknown. We present 2 Native American families with a total of 5 affected persons and a single affected patient of Pakistani origin in which GPS appears to be inherited in an autosomal recessive manner. Homozygosity mapping using the Affymetrix 6.0 chips demonstrates that all 6 GPS-affected persons studied are homozygous for a 1.7-Mb region in 3p21. Linkage analysis confirmed the region with a logarithm of the odds score of 2.7. Data from our families enabled us to significantly decrease the size of the critical region for GPS from the previously reported 9.4-Mb region at 3p21.
Blood 01/2011; 117(12):3430-4. · 9.90 Impact Factor
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Walter H A Kahr,
Jesse Hinckley,
Ling Li,
Hansjörg Schwertz,
Hilary Christensen,
Jesse W Rowley,
Fred G Pluthero,
Denisa Urban,
Shay Fabbro,
Brie Nixon, [......],
Mike Storck,
Kai Wang,
Gi-Yung Ryu,
Shawn M Jobe,
Brian C Schutte,
Jack Moseley,
Noeleen B Loughran,
John Parkinson,
Andrew S Weyrich, Jorge Di Paola
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ABSTRACT: Next-generation RNA sequence analysis of platelets from an individual with autosomal recessive gray platelet syndrome (GPS, MIM139090) detected abnormal transcript reads, including intron retention, mapping to NBEAL2 (encoding neurobeachin-like 2). Genomic DNA sequencing confirmed mutations in NBEAL2 as the genetic cause of GPS. NBEAL2 encodes a protein containing a BEACH domain that is predicted to be involved in vesicular trafficking and may be critical for the development of platelet α-granules.
Nature Genetics 01/2011; 43(8):738-40. · 35.53 Impact Factor
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ABSTRACT: The last significant advance in the therapy of hemophilia B was the introduction of recombinant factor IX (FIX), ensuring an advanced level of safety from potential infectious contaminants of plasma-derived clotting factors. Since that time, recombinant DNA techniques have been applied in research to elucidate the role of FIX and its functional domains within coagulation. At the same time, recombinant DNA technology has been applied to engineer an expanding spectrum of novel FIX therapies that are now being translating into clinical trials. The experience with the existing recombinant FIX product is reviewed with a focus on the novel products and the potential to improve the quality of life for individuals with hemophilia B.
Seminars in Thrombosis and Hemostasis 07/2010; 36(5):498-509. · 4.52 Impact Factor
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ABSTRACT: Predicting the clinical effect of bypassing agents such as recombinant activated factor VII in haemophilia patients with inhibitors is hampered by the limited availability of reliable laboratory monitoring tools. This multicentre, open-label trial aimed to explore the dose-response relationship between recombinant activated factor VII concentration and thromboelastography parameters in blood samples from patients with haemophilia A or B with inhibitors in a nonbleeding state. Citrated whole blood samples from 16 patients (>or=16 years) with haemophilia A or B were spiked ex vivo with recombinant activated factor VII (1.2, 1.6, 2.0, 2.6, 3.0, 3.5 microg/ml), corresponding approximately to doses of 90-270 microg/kg. Samples were analysed by Thromboelastograph or Rotation Thromboelastography (three United States and three European centres, respectively) within 30 min (final lipidated recombinant tissue factor 1: 17 000; final CaCl2 15 mM). Thromboelastograph/Rotation Thromboelastography parameters showed large intersubject variation in the baseline profiles. There was a clear effect when recombinant activated factor VII was added; however, a clear concentration-response relationship was only detected for one patient. This is likely due to the fact that the curves were not sufficiently abnormal that led to reduced assay sensitivity. Our preliminary results suggest that thromboelastography may potentially be a clinically useful tool for monitoring changing concentrations of recombinant activated factor VII in haemophilia patients, but only when the baseline curve is significantly abnormal. Thus, test conditions may need to be optimized before Thromboelastograph/Rotation Thromboelastography can be utilized for all inhibitor patients.
Blood Coagulation and Fibrinolysis 07/2008; 19(4):276-82. · 1.24 Impact Factor
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ABSTRACT: Tosetto and colleagues have developed a mathematical method to quantify the odds of having type 1 von Willebrand Disease based on a person's family history, bleeding score, and VWF level.
Blood 05/2008; 111(8):3919-20. · 9.90 Impact Factor
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ABSTRACT: Many of the cellular responses that occur in activated platelets resemble events that take place following activation of cell-death pathways in nucleated cells. We tested the hypothesis that formation of the mitochondrial permeability transition pore (MPTP), a key signaling event during cell death, also plays a critical role in platelet activation. Stimulation of murine platelets with thrombin plus the glycoprotein VI agonist convulxin resulted in a rapid loss of mitochondrial transmembrane potential (Deltapsi(m)) in a subpopulation of activated platelets. In the absence of cyclophilin D (CypD), an essential regulator of MPTP formation, murine platelet activation responses were altered. CypD-deficient platelets exhibited defects in phosphatidylserine externalization, high-level surface fibrinogen retention, membrane vesiculation, and procoagulant activity. Also, in CypD-deficient platelet-rich plasma, clot retraction was altered. Stimulation with thrombin plus H(2)O(2), a known activator of MPTP formation, also increased high-level surface fibrinogen retention, phosphatidylserine externalization, and platelet procoagulant activity in a CypD-dependent manner. In a model of carotid artery photochemical injury, thrombosis was markedly accelerated in CypD-deficient mice. These results implicate CypD and the MPTP as critical regulators of platelet activation and suggest a novel CypD-dependent negative-feedback mechanism regulating arterial thrombosis.
Blood 03/2008; 111(3):1257-65. · 9.90 Impact Factor
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ABSTRACT: Platelet activation in response to dual stimulation with collagen and thrombin results in the formation of a subpopulation of activated platelets known as coated platelets. Coated platelets are characterized by high surface levels of alpha-granule proteins and phosphatidylserine, which support the assembly of procoagulant protein complexes. Using murine models, we tested the hypothesis that the collagen receptor-associated molecule FcRgamma and the transglutaminase factor XIIIA are required for the formation of coated platelets. Following dual stimulation with the collagen receptor agonist convulxin and thrombin, 68% of platelets from C57BL/6 mice acquired the coated platelet phenotype, defined by high surface levels of fibrinogen and von Willebrand factor and decreased binding of the alphaIIbbeta3 activation-dependent antibody PE-JON/A. In FcRgamma-/- mice, only 10% of platelets became "coated" after dual stimulation with convulxin plus thrombin (P < .05 vs C57BL/6 platelets). Decreased coated platelet formation in FcRgamma-/- platelets was accompanied by decreased annexin V binding (P < .01) and decreased platelet procoagulant activity (P < .05). Platelets from FXIIIA-/- mice did not differ from control platelets in coated platelet formation or annexin V binding. We conclude that FcRgamma, but not factor XIIIA, is essential for formation of highly procoagulant coated platelets following dual stimulation with collagen and thrombin.
Blood 01/2006; 106(13):4146-51. · 9.90 Impact Factor
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Jorge Di Paola
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ABSTRACT: von Willebrand disease (VWD) is one of the most common bleeding disorders. It is caused by abnormalities in the von Willebrand factor (VWF) protein, and is characterized by incomplete penetrance and variable expressivity. VWF levels vary widely in the population. The best-characterized human genetic modifier of VWF is the ABO blood group. Patients with VWD show considerable variation in bleeding tendency even within the same family, independently of VWF levels. It is possible that several modifier genes influence the phenotype. Variants of genes that encode for platelet receptors as well as those that encode for clotting factor levels have been proposed as modifiers. It is hoped that new clinical-genetic studies will shed light on these issues and help practitioners to determine the population at risk for bleeding.
Current hematology reports 10/2005; 4(5):345-9.
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Amy D Shapiro, Jorge Di Paola,
Alice Cohen,
K John Pasi,
Margaret A Heisel,
Victor S Blanchette,
Thomas C Abshire,
W Keith Hoots,
Jeanne M Lusher,
Claude Negrier,
Chantal Rothschild,
David A Roth
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ABSTRACT: This international clinical trial evaluated the safety and efficacy of recombinant factor IX (rFIX) in previously untreated patients (PUPs) with severe or moderately severe hemophilia B (FIX activity, < or = 3 IU/dL). Sixty-three PUPs aged younger than 1 month to 14 years received rFIX (median treatment duration, 37 months; range, 4-64 months). Mean rFIX recovery (0.68 +/- 0.27 IU/dL per IU/kg) remained constant over 5 years and was similar in infants (1 month to < 2 years) and children (2 to < 12 years). Fifty-four PUPs used rFIX (median dose, 62.7 IU/kg per infusion; range, 8.2-292 IU/kg) to treat 997 hemorrhages. Bleeding was well controlled, with 75% of hemorrhages requiring only one rFIX infusion. Response to rFIX was "excellent" or "good" in 94% of cases. Effective hemostasis was achieved in 32 PUPs receiving rFIX for routine prophylaxis, with 91% of prophylaxis responses rated "excellent." rFIX administered for 30 surgical procedures in 23 PUPs achieved hemostasis for all rated procedures. Five patients experienced allergic-type manifestations, including 2 (3%) patients who developed FIX inhibitors (both > 5 BU/dL). rFIX was well tolerated, with no associated thrombotic events or evidence of viral transmission. These data indicate that rFIX is a safe and effective treatment for PUPs with hemophilia B.
Blood 02/2005; 105(2):518-25. · 9.90 Impact Factor
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Jorge Di Paola
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ABSTRACT: Issues that may influence selection of a factor concentrate for treatment of patients with hemophilia B, including whether the product is derived from plasma or is of recombinant origin, costs, pharmacokinetic issues, and safety considerations, are discussed in this paper. Data in the published literature, advice from the medical team, and patient and family preferences, will also impact product choice. Plasma-derived and recombinant products have similar efficacy; however, recombinant concentrates are more expensive and have demonstrated lower post-infusion recovery, and plasma-derived concentrates may be perceived as less safe. Improvements in donor selection and testing, viral inactivation, and product purification have greatly reduced potential risks of plasma-derived products. It is expected that both recombinant and plasma-derived products will continue to be used worldwide in the treatment of hemophilia B.
Blood Coagulation and Fibrinolysis 07/2004; 15 Suppl 2:S17-8. · 1.24 Impact Factor
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ABSTRACT: The adapter protein SLP-76 is a critical mediator of signal transduction via the platelet collagen receptor glycoprotein VI (GPVI) and its coreceptor FcRgamma. We tested the hypothesis that SLP-76 is required for collagen-induced procoagulant responses in murine platelets. Platelets from SLP-76 null (SLP-76(-/-)) or heterozygous (SLP-76(+/-)) mice were activated with the GPVI agonist convulxin, and surface expression of P-selectin (a marker of granule release) and annexin V binding (a marker of procoagulant phospholipid) were determined by flow cytometry. Convulxin induced surface expression of P-selectin in SLP-76(+/-) platelets, but not SLP-76(-/-) platelets (P <.01), and failed to stimulate annexin V binding to either SLP-76(+/-) or SLP-76(-/-) platelets. Platelet procoagulant activity was measured in a prothrombinase assay. Convulxin did not stimulate procoagulant activity in either SLP-76(+/-) or SLP-76(-/-) platelets, but fibrillar collagen produced a 1.9-fold increase in procoagulant activity in both SLP-76(+/-) and SLP-76(-/-) platelets (P <.001 versus unstimulated platelets). Similar results were obtained with platelets from FcRgamma null mice, for which collagen, but not convulxin, induced procoagulant activity (P <.01). Costimulation with thrombin and collagen produced a further (2.3-fold) increase in procoagulant activity in SLP-76(+/-) platelets (P <.05), but not in SLP-76(-/-) platelets. SLP-76(-/-) platelets also exhibited less annexin V binding than SLP-76(+/-) platelets after costimulation with thrombin and convulxin (P <.05). These findings demonstrate that an intact GPVI/FcRgamma/SLP-76 signal transduction pathway is not essential for platelet procoagulant activity induced by collagen but is necessary for maximal procoagulant response to costimulation with thrombin plus collagen. Thus, both GPVI-dependent and GPVI-independent pathways contribute to collagen-induced platelet procoagulant activity.
Blood 11/2002; 100(8):2839-44. · 9.90 Impact Factor
