1/45. Fibrinogen St. Gallen I (gamma 292 Gly--> Val): evidence for structural alterations causing defective polymerization and fibrinogenolysis.Fibrinogen St. Gallen I was detected in an asymptomatic Swiss woman. Routine coagulation tests revealed a prolonged thrombin and reptilase time. Functionally measured fibrinogen levels were considerably lower than those determined immunologically. polymerization of fibrin monomers derived from purified fibrinogen was delayed in the presence of either calcium or EDTA. Normal fibrinopeptide a and B release by thrombin was established. An abnormal degradation of fibrinogen St. Gallen I by plasmin was observed. Fragment D1 of normal fibrinogen was fully protected against further proteolysis in the presence of 10 mM calcium, whereas fibrinogen St. Gallen I was partially further degraded to fragments D2 and D3. In the presence of 10 mM EDTA, the conversion of variant fragment D1 to D2 was accelerated whereas the degradation of fragment D2 to D3 was delayed in comparison to degradation of fragments D1 and D2 of normal fibrinogen. Three high-affinity calcium binding sites were found in both normal and variant fibrinogen. Mutation screening with SSCP analysis suggested a mutation in exon VIII of the gamma-chain gene. Cycle sequencing of this gene portion revealed a single base substitution from G to T of the base 7527, leading to replacement of gamma 292 glycine by valine. The same mutation has already been described for the fibrinogen variant baltimore I. Molecular modeling was performed of a part of the gamma-chain containing the mutation site, based on recently published X-ray crystal structures of human fibrinogen fragment D and of a 30 kD C-terminal part of the gamma-chain. Significant structural alterations due to the substitution of glycine by valine at gamma 292 were observed, e.g. spreading of the protein backbone, probably leading to a modified accessibility of the plasmic cleavage sites in the gamma-chain at 356 Lys and 302 Lys. A shift of gamma 297 Asp that is involved in interactions of fragment D with the Gly-Pro-Arg-Pro-peptide was noted by molecular modeling. The latter observation is compatible with delayed polymerization of fibrin monomers.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
2/45. Recurrent spontaneous intracerebral hemorrhage in a congenitally afibrinogenemic patient: diagnostic pitfalls and therapeutic options.BACKGROUND: Coagulation disorders can cause intracerebral bleeding that may be difficult to detect since subsequent aberrant clot formation may mask early detection. This is an important pitfall because, when diagnosed early, bleeding in these patients is treatable. CASE DESCRIPTION: A patient with congenital afibrinogenemia presented with recurrent hemiparesis. Spontaneous intracerebral hemorrhage was diagnosed, despite an initial negative CT scan. Diagnosis, therapy, and complications of therapy are discussed. CONCLUSIONS: Intracerebral hemorrhage must be strongly suspected in any patient with a coagulation disorder presenting with matching clinical symptoms. Therapy must be installed immediately, before additional investigations, and should be continued even when initial neuroimaging is negative.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
3/45. Embolized ischemic lesions of toes in an afibrinogenemic patient: possible relevance to in vivo circulating thrombin.Fibrinogen plays a complex role in hemostasis, thrombosis, and vascular disease. Hyperfibrinogenemia is an independent vascular risk factor and dysfibrinogenemia can provoke thrombosis. afibrinogenemia is usually responsible for hemorrhagic diathesis, and unexpected ischemic lesions are intriguing. We report the case of an afibrinogenemic patient, who at the age of 30 developed ischemic lesions of the feet related to severe stenosis of the iliac and hypogastric arteries. The biopsy of the iliac artery lesion showed an intense myointimal hyperplasia. We performed standard hemostatic analysis and analyzed the activation markers of platelets and coagulation factors and the kinetics of thrombin generation in the patient and in normal control plasmas treated or not with reptilase. Occlusive arterial lesions were attributed to a disruptive hematoma penetrating the vascular lumen. Thrombin concentration after calcium addition increase markedly in the afibrinogenemic patient and in defibrinated normal plasma, as compared to untreated normal plasma. Thrombin-antithrombin complexes (T-AT) were markedly enhanced while F1 2 prothrombin fragments stayed in the normal range. These results suggested activation of coagulation and in vivo circulating thrombin. Thrombin activates the platelets that secrete growth factors for smooth muscle cells and generate the intimal hyperplasia. Recurrent hemorrhage within the vessel wall might induce injury and local thrombin generation. Thrombin not trapped by the clot is available for platelet activation and smooth muscle cell migration and proliferation. The absence of a protective fibrin cap on the intima might account for intima vulnerability and embolization. afibrinogenemia appears in this paradoxical situation as a vascular risk factor.- - - - - - - - - - ranking = 2keywords = coagulation (Clic here for more details about this article) |
4/45. Cytoplasmic inclusion bodies and minimal hepatitis: fibrinogen storage without hypofibrinogenemia.A 12-year-old Japanese boy had chronic elevation and fluctuation of serum transaminase levels since infancy, with no signs or symptoms of liver failure. Usual infections or metabolic disorders were eliminated from consideration. No coagulopathy or abnormality in plasma concentrations of clotting factors was found. light microscopy of liver biopsy specimens obtained at ages 2, 5, and 7 years showed slight hepatocyte disarray and minimal mononuclear-leukocyte lobular inflammation, with eosinophilic inclusion bodies in the cytoplasm of hepatocytes throughout the lobule. These bodies stained with the periodic acid-Schiff (PAS) technique; the PAS-positive material was partly diastase digestible and on immunostaining marked for fibrinogen but not for alpha 1-antitrypsin. On transmission electron microscopy, the bodies were represented by finely granular material contained within membranes and were interpreted as tentatively endoplasmic reticulum. Fibrinogen storage may be manifest as minimal hepatitis without coagulopathy.- - - - - - - - - - ranking = 0.99254026132387keywords = coagulopathy (Clic here for more details about this article) |
5/45. A frameshift mutation in the human fibrinogen Aalpha-chain gene (Aalpha(499)Ala frameshift stop) leading to dysfibrinogen San Giovanni Rotondo.We have investigated a 53-yr-old asymptomatic white man with decreased functional, but not immunologic, fibrinogen plasma levels together with prolonged thrombin and reptilase times, detected through routine coagulation studies prior to a surgical procedure. A new heterozygous single nucleotide deletion (C) at position Ala499 within the Aalpha-chain gene was identified, which predicted changes of the corresponding amino acids encoded by the subsequent portion of the exon V and the appearance of a premature stop codon at position 518 (Aalpha[499]Ala frameshift stop). The new dysfunctional fibrinogen, San Giovanni Rotondo variant, was confirmed in vivo by SDS-PAGE analysis of HPLC-purified fibrinogen chains. Mass spectrum examination of the abnormal HPLC-purified peak gave an estimated mass (56,088 Da) similar to that predicted by dna analysis of the mutated Aalpha-chain gene (56,088 Da) and, after tryptic digestion, the truncated Aalpha-chain was shown only in the propositus, who also carried normal Aalpha-chain. In addition, mass spectrum analysis of the tryptic digest of the abnormal chain confirmed the presence of a new and unpaired cysteine at the last position that was predicted to form a disulfide bridge with human serum albumin. Immuno-blot analysis confirmed that fibrinogen San Giovanni Rotondo variant, but not normal fibrinogen. contained substantial amounts of albumin. Present findings confirm that truncated Aalpha-chain lacking part of the terminal domain may be incorporated into mature fibrinogen molecules and normally secreted in the bloodstream.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
6/45. leg ulcer presenting in a patient with congenital afibrinogenaemia.Congenital afibrinogenaemia is a rare hemorrhagic disorder characterized by the absence of fibrinogen. We report a case of congenital afibrinogenaemia presented with leg ulcer. A 30-year-old man presented with a history of prolonged bleeding from birth. His parents are cousins. He repeatedly showed haematoma after traumas on his leg. He was diagnosed as having congenital afibrinogenaemia because of plasma fibrinogen deficiency. Because his leg ulcer gradually increased in size, he was admitted to our department for treatment. Laboratory examinations revealed prolonged bleeding time, prolonged coagulation time, prolonged prothrombin time, prolonged activated partial thromboplastin time and plasma fibrinogen was not measurable. Histological examination revealed hyperkeratosis, acanthosis and severe fibrotic change in the whole dermis. Severe hemosiderin deposit was found in the middle dermis. His leg ulcer cured 2 months after the beginning of fresh frozen plasma administration (FFP), but recurrence of the leg ulcer after FFP treatment was found. This is the second reported case of congenital afibrinogenaemia presented with leg ulcer.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
7/45. Analysis of Iranian patients allowed the identification of the first truncating mutation in the fibrinogen Bbeta-chain gene causing afibrinogenemia.BACKGROUND AND OBJECTIVES: Congenital afibrinogenemia is a rare coagulation disorder whose molecular basis is still poorly characterized. Most mutations have been identified in the fibrinogen Aalpha- and gamma-chain genes, whereas only two missense mutations have been reported in the Bbeta-chain gene. The aim of this work was to widen knowledge about the mutational spectrum of this disease by analyzing the molecular bases of congenital afibrinogenemia in three unrelated Iranian patients. DESIGN AND methods: All patients showed unmeasurable levels of clottable fibrinogen in plasma. Mutational screening was performed by sequencing the whole coding region, including exon-intron boundaries and part of the promoter region of the three fibrinogen genes. RESULTS: Sequencing in one patient revealed the presence of a novel nonsense mutation (3282C-->T) in exon 2 of the fibrinogen Bbeta-chain gene, causing a severe truncation of the corresponding polypeptide (R17X). In the remaining probands, two already known small deletions (4209delA and 4220delT), both located in exon 5 of the fibrinogen Aalpha-chain gene, were identified, and their effect at the protein level explored by computer-assisted analysis. INTERPRETATION AND CONCLUSIONS: The identification of the first truncating mutation in the fibrinogen Bbeta-chain gene confirms the involvement of all three fibrinogen genes in the pathogenesis of congenital afibrinogenemia and widens the mutational spectrum of the disease. This knowledge is clinically essential in order to carry out prenatal diagnosis in families at risk.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
8/45. Congenital afibrinogenemia: first identification of splicing mutations in the fibrinogen Bbeta-chain gene causing activation of cryptic splice sites.Congenital afibrinogenemia is a rare inherited coagulopathy, characterized by very low or unmeasurable plasma levels of immunoreactive fibrinogen. So far, 25 mutations have been identified in afibrinogenemia, 17 in the Aalpha, 6 in the gamma, and only 2 in the Bbeta fibrinogen-chain genes. Here, 2 afibrinogenemic probands, showing undetectable levels of functional fibrinogen, were screened for causative mutations at the genomic level. sequence analysis of the 3 fibrinogen genes disclosed 2 novel homozygous mutations in introns 6 and 7 of the Bbeta-chain gene (IVS6 13C > T and IVS7 1G > T), representing the first Bbeta-chain gene splicing mutations described in afibrinogenemia. The IVS6 13C > T mutation predicts the creation of a donor splice site in intron 6, whereas the IVS7 1G > T mutation causes the disappearance of the invariant GT dinucleotide of intron 7 donor splice site. To analyze the effect of these mutations, expression plasmids containing Bbeta-chain minigene constructs, either wild-type or mutant, were transfected in hela cells. Assessed by semiquantitative analysis of reverse transcriptase-polymerase chain reaction products, the IVS7 1G > T mutation resulted in multiple aberrant splicings, while the IVS6 13C > T mutation resulted in activation of a new splice site 11 nucleotides downstream of the physiologic one. Both mutations are predicted to determine protein truncations, supporting the importance of the C-terminal domain of the Bbeta chain for fibrinogen assembly and secretion.- - - - - - - - - - ranking = 0.49627013066193keywords = coagulopathy (Clic here for more details about this article) |
9/45. Identification of simultaneous mutation of fibrinogen alpha chain and protein C genes in a Japanese kindred.Afibrinogenaemia usually induces a bleeding tendency during infancy, whereas protein c deficiency increases susceptibility to thrombosis in children or adolescence. Mutations of these genes have been, therefore, established as independent risk factors for coagulation disorders. We describe the homozygous mutation of the fibrinogen alpha chain gene and additional heterozygous mutation of the protein C gene in a male infant who showed prolonged umbilical bleeding after birth. On examination, the plasma fibrinogen was undetectable, and the activity and antigen level of protein C were reduced. The patient showed no fibrinogen Aalpha chain as well as Bbeta and gamma chains by Western blotting. The sequencing analysis showed the homozygous deletion of 1238 bases from intron 3 at position 2008 to intron 4 at position 3245 in the fibrinogen alpha chain gene. Both parents were heterozygous carriers of this mutation. In this patient, an additional mutation was also detected in the protein C gene: the heterozygous deletion of exon 7 at position 6161-6163 or 6164-6166, resulting the deletion of one amino acid (Lys150 or 151). His mother was also a carrier of this mutation. As the simultaneous mutation of the fibrinogen alpha chain and protein C genes has not been previously reported, the influence of the interaction between these two mutations on the clinical manifestations of this patient should be carefully monitored for a long period.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
10/45. 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.- - - - - - - - - - ranking = 1keywords = coagulation (Clic here for more details about this article) |
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