1/51. Homozygous Cys542-->Arg substitution in GPIIIa in a Swiss patient with type I Glanzmann's thrombasthenia.Glanzmann's thrombasthenia (GT) arises from a qualitative or quantitative defect in the GPIIb-IIIa complex (integrin alphaIIbbeta3), the mediator of platelet aggregation. We describe a patient in whom clinical and laboratory findings typical of type I GT were found together with a second pathology involving neurological and other complications symptomatic of tuberous sclerosis. Analysis of platelet proteins by Western blotting revealed trace amounts of normally migrating GPIIb and equally small amounts of GPIIIa of slightly slower than normal migration. flow cytometry confirmed a much decreased binding to platelets of monoclonal antibodies to GPIIb, GPIIIa or GPIIb-IIIa, and an antibody to the alphav subunit also showed decreased binding. Nonradioactive PCR single-strand conformation polymorphism analysis followed by direct sequencing of PCR-amplified dna fragments showed a homozygous point mutation (T to C) at nucleotide 1722 of GPIIIa cDNA and which led to a Cys542-->Arg substitution in the GPIIIa protein. The mutation gave rise to a HinP1 I restriction site in exon 11 of the GPIIIa gene and allele-specific restriction enzyme analysis of family members confirmed that a single mutated allele was inherited from each parent. This amino acid substitution presumably changes the capacity for disulphide bond formation within the cysteine-rich core region of GPIIIa and its study will provide new information on GPIIb-IIIa and alphavbeta3 structure and biosynthesis.- - - - - - - - - - ranking = 1keywords = complex (Clic here for more details about this article) |
2/51. Glanzmann's thrombasthenia in pregnancy: a case and review of the literature.Glanzmann's thrombasthenia is a rare autosomal recessive bleeding disorder resulting from a deficiency of glycoprotein IIb-IIIa complex in platelets. The deficient complex normally mediates platelet aggregation by binding adhesive proteins, which form bridges between activated cells. Despite normal platelet counts, morphology, prothrombin, and activated thromboplastin times, Glanzmann's thrombasthenia is characterized by a prolonged bleeding time and a severe hemorrhagic mucocutaneous diasthesis. pregnancy and delivery are rare in these patients and have been associated with a high risk of severe hemorrhage. We present an unusual case in which a primi-gravida patient with Glanzmann's thrombasthenia underwent an uneventful pregnancy and spontaneous vaginal delivery, following intrapartum intravenous administration of single-donor platelets. Subsequent late postpartum hemorrhage required intravenous transfusion of an additional unit of single-donor platelets. In addition, we review the literature pertaining to pregnancy and Glanzmann's thrombasthenia with an emphasis on intrapartum prophylactic management.- - - - - - - - - - ranking = 2keywords = complex (Clic here for more details about this article) |
3/51. A naturally occurring mutation near the amino terminus of alphaIIb defines a new region involved in ligand binding to alphaIIbbeta3.Decreased expression of functional alphaIIbbeta3 complexes on the platelet surface produces Glanzmann thrombasthenia. We have identified mutations of alphaIIb(P145) in 3 ethnically distinct families affected by Glanzmann thrombasthenia. Affected Mennonite and Dutch patients were homozygous and doubly heterozygous, respectively, for a P(145)A substitution, whereas a Chinese patient was doubly heterozygous for a P(145)L substitution. The mutations affect expression levels of surface alphaIIbbeta3 receptors on their platelets, which was confirmed by co-transfection of alphaIIb(P145A) and beta3 cDNA constructs in COS-1 cells. Each mutation also impaired the ability of alphaIIbbeta3 on affected platelets to interact with ligands. Moreover, when alphaIIb(P145A) and beta3 were stably coexpressed in Chinese hamster ovary cells, alphaIIbbeta3 was readily detected on the cell surface, but the cells were unable to adhere to immobilized fibrinogen or to bind soluble fluorescein isothiocyanate-fibrinogen after alphaIIbbeta3 activation by the activating monoclonal antibody PT25-2. Nonetheless, incubating affected platelets with the peptide LSARLAF, which binds to alphaIIb, induced PF4 secretion, indicating that the mutant alphaIIbbeta3 retained the ability to mediate outside-in signaling. These studies indicate that mutations involving alphaIIb(P145 )impair surface expression of alphaIIbbeta3 and that the alphaIIb(P145A) mutation abrogates ligand binding to the activated integrin. A comparative analysis of other alphaIIb mutations with a similar phenotype suggests that these mutations may cluster into a single region on the surface of the alphaIIb and may define a domain influencing ligand binding. (blood. 2000;95:180188)- - - - - - - - - - ranking = 1keywords = complex (Clic here for more details about this article) |
4/51. bone marrow transplantation in severe Glanzmann's thrombasthenia with antiplatelet alloimmunization.Glanzmann's thrombasthenia is an autosomal recessive disorder characterized by a lack of platelet aggregation due to the absence of platelet glycoprotein IIb and IIIa. Usually, the disease leads to mild hemorrhage but sometimes bleeding is severe enough to be life-threatening. We report the case of a 16-year-old girl, presenting with very severe type 1 Glanzmann's thrombasthenia, successfully treated with an HLA-identical sibling bone marrow transplant (BMT). We also update the clinical and laboratory data of her brother, who had received a BMT 16 years ago for the same disease. In the light of these two cases and two others published in the literature, we discuss the indications for BMT from HLA-identical sibling donors in Glanzmann's thrombasthenia. Alloimmunization against the missing platelet GPIIb/IIIa complex and severity of bleeding episodes may constitute sufficient criteria for allogeneic BMT after careful assessment of the risk-benefit of such a procedure, although this remains exceptional in this disease. bone marrow transplantation (2000) 25, 327-330.- - - - - - - - - - ranking = 1keywords = complex (Clic here for more details about this article) |
5/51. A 1063G-->A mutation in exon 12 of glycoprotein (GP)IIb associated with a thrombasthenic phenotype: mutation analysis of [324E]GPIIb.We report the molecular, genetic and functional analysis of a case of thrombasthenic phenotype. The proband showed absence of platelet glycoprotein (GP)IIb and very low content of GPIIIa, and both his parents showed a marked reduction in the levels of platelet GPIIb-IIIa. Single-stranded conformational polymorphism-polymerase chain reaction (SSCP-PCR) analysis and direct sequencing of PCR-amplified GPIIb exon-12 revealed the presence of a G-->A transition at position 1063 with the expected substitution of glutamate 324 with lysine (K). This mutation did not alter the level of GPIIb mRNA. Co-expression of normal or mutant [324K] GPIIb with normal human GPIIIa in Chinese hamster ovary (CHO) cells failed to show surface exposure of [324K]GPIIb-IIIa complexes. pulse-chase and immunoprecipitation analysis demonstrated that [324K]GPIIb cDNA was translated into proGPIIb, but neither mutant GPIIb heavy chain (GPIIbH) nor [324K]GPIIb-GPIIIa complexes were detected, suggesting that this mutation is the underlying molecular basis for the thrombasthenic phenotype. Mutation analysis demonstrated that 324E of GPIIb could be replaced by other negatively charged or polar amino acids (AAs) without impairing the surface expression of GPIIb-IIIa. However, substitution of 324E of GPIIb for a positively charged AA other than K prevented the expression of GPIIb-IIIa complexes. These observations suggest that a domain encompassing 324E of GPIIb is essential for heterodimerization with GPIIIa and its substitution for a positively charged residue precludes normal subunit association.- - - - - - - - - - ranking = 3keywords = complex (Clic here for more details about this article) |
6/51. Nonsense mutation in exon-19 of GPIIb associated with thrombasthenic phenotype. Failure of GPIIb(delta597-1008) to form stable complexes with GPIIIa.We report the molecular genetic analysis of a patient with thrombasthenic phenotype. The lack of surface platelet GPIIb-IIIa complexes and the presence of GPIIIa suggested it was a case of type I Glanzmann's thrombasthenia due to a mutation in GPIIb. Single stranded conformational polymorphism analysis (SSCP) of exon-19 of GPIIb showed polymorphic dna bands. The dna sequence of exon-19 revealed the presence of a homozygous C1882T transition that changes residue R597 to STOP codon. Since no other mutations were found in either GPIIb or GPIIIa it is concluded that the C1882T substitution in GPIIb is responsible for the thrombasthenic phenotype of the patient. The lack of platelet GPIIb-mRNA in the proband indicates instability of the [C1882T]GPIIb-mRNA. Coexpression of normal GPIIIa and GPIIb(delta597-1008) in cho cells failed to show surface expression of GPIIb(delta597-1008)-IIIa complexes. immunoprecipitation analysis demonstrated that GPIIb(delta597-1008) may indeed complex GPIIIa; however, the association is either unstable or incapable of progressing along the secretory pathway.- - - - - - - - - - ranking = 7keywords = complex (Clic here for more details about this article) |
7/51. A Leu55 to Pro substitution in the integrin alphaIIb is responsible for a case of Glanzmann's thrombasthenia.Glanzmann's thrombasthenia (GT) is a hereditary bleeding disorder caused by a quantitative or qualitative defect in the integrin alphaIIbbeta3. A new mutation, a T to C substitution at base 258 in the alphaIIb gene, leading to the replacement of Leu55 with Pro, was found by sequence analysis of a patient's alphaIIb cDNA. In transfection experiments using COS7 cells, the cells co-transfected with the mutated alphaIIb cDNA containing C258 and wild-type beta3 cDNA scarcely expressed the alphaIIbbeta3 complex. The Leu55 to Pro substitution in the alphaIIb gene was found to be responsible for this case of Glanzmann's thrombasthenia.- - - - - - - - - - ranking = 1keywords = complex (Clic here for more details about this article) |
8/51. Successful surgery using recombinant factor viia for recurrent, idiopathic nonulcer duodenal bleeding in a patient with Glanzmann's thrombasthenia.A 68-year-old man with Glanzmann's thrombasthenia suffered from recurrent cryptogenic bleeding originating in the upper duodenal flexure. Extensive endoscopic procedures and medical treatments were unsuccessful and proximal duodenectomy was proposed. In preceding years platelet transfusions had often had a suboptimal result and were complicated by allergic reactions. Surgery was carried out while he was being treated with recombinant factor viia. Neither major blood loss nor other complications occurred. Histological examination of the bleeding site failed to show abnormalities and the nature of this patient's bleeding problem remained unexplained. Glanzmann's thrombasthenia is a rare autosomal recessive disorder of platelet aggregation characterized by a lifelong bleeding tendency due to abnormalities of the glycoprotein IIb-IIIa membrane complex. Common clinical manifestations include purpuric type bleeding, epistaxis, menorrhagia and gingival bleeding. Spontaneous bleeding is uncommon but posttraumatic and postoperative hemorrhage may be particularly serious. There is no specific treatment. Prophylactic and therapeutic platelet transfusions are the cornerstone of supportive treatment. In many patients the efficacy of this approach is diminished by allo-anti-platelet antibodies. We report on a patient with Glanzmann's disease with recurrent nonulcer duodenal bleeding refractory to conservative medical treatment. Despite documented suboptimal effectiveness of platelet transfusions, he underwent successful surgery with administration of recombinant factor viia (rFVIIa).- - - - - - - - - - ranking = 1keywords = complex (Clic here for more details about this article) |
9/51. Pyelolithotomy in a patient with Glanzmann thrombasthenia and antiglycoprotein IIb/IIIa antibodies: the shortest possible duration of treatment with recombinant activated factor VII and platelet transfusions.Transfusion of platelet concentrates remains the first-line therapy for Glanzmann thrombasthenia in case of bleeding or preparation for surgery. However, development of antibodies to platelet glycoprotein (Gp) IIb/IIIa complex or human leukocyte antigens (HLA) is frequent and the main cause of platelet refractoriness. Recombinant activated factor VII (rFVIIa) is a potent alternative for patients with Glanzmann thrombasthenia with anti-platelet antibodies. We describe a case of Glanzmann thrombasthenia with alloantibodies to platelet Gp IIb/IIIa complex who underwent a successful pyelolithotomy operation under the coverage of recombinant activated factor viia and platelet transfusions.- - - - - - - - - - ranking = 2keywords = complex (Clic here for more details about this article) |
10/51. Molecular basis for Glanzmann's thrombasthenia (GT) in a compound heterozygote with glycoprotein IIb gene: a proposal for the classification of GT based on the biosynthetic pathway of glycoprotein IIb-IIIa complex.The genetic basis for Glanzmann's thrombasthenia (GT) was elucidated on a compound heterozygote with glycoprotein (GP)IIb gene: an opal mutation at the end of exon 17 (CGA TGA) results in only a trace amount of GPIIb mRNA, and a splicing mutation at the acceptor site of exon 26 (CAG GAG) causes an in-frame, exon skipping process from exon 25 to 27. This aberrant transcript encodes a single-chain polypeptide characterized by a 42-amino acid deletion, which includes the proteolytic cleavage site(s) and a unique, proline-rich region at the location corresponding to the carboxyl-terminal of the normal GPIIb alpha-chain. These characteristics are shared by a previously reported defective GPIIb molecule, which is neither assembled with GPIIIa nor transported to the cellular surface. Despite its normal transcription level, expression of the present defective GPIIb molecule was significantly decreased (approximately 6% of the control level). Because the precursor GPIIb molecule is assembled with GPIIIa in the endoplasmic reticulum (ER) and its processing, as well as stability, is dependent on the GPIIIa subunit, the defective GPIIb molecule may be rapidly degraded by the intrinsic quality control system of the ER due to its inability to form a stable heterodimer complex as a consequence of its misfolded structure. Although we did not confirm that the GPIIIa genes of this individual were normal, GPIIIa may be secondarily decreased (approximately 11% of control), because a large part of it could not be complexed, making it vulnerable to proteolysis. To elucidate the molecular basis for GT, we propose here a classification of GT based on the biosynthetic pathway of the GPIIb-IIIa complex.- - - - - - - - - - ranking = 7keywords = complex (Clic here for more details about this article) |
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