[Study of the inhibitor of familial factor V deficiency. II].
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To investigate the molecular defects in two Chinese pedigrees with inherited factor V (FV) deficiency. A 37-year-old male (proband 1) and an 18-month-old boy (proband 2) were diagnosed as inherited coagulation FV deficiency by severely reduced plasma levels of FV activity and antigen. All 25 exons and their flanking sequence of F5 gene were amplified by polymerase chain reaction (PCR) for both probands and the PCR products were directly sequenced. Total RNA was extracted from the peripheral lymphocytes of proband 1 for detecting the changes at mRNA level. The homozygous deletion IVS8 -2A>G was identified in the F5 gene of proband 1 and complementary DNA (cDNA) analysis revealed the abolishment of the canonical splicing site by the mutation and the activation of the cryptic acceptor site 24 bp upstream instead. The insertion introduced eight additional amino acids (AA) into the FV protein. Two heterozygous mutations of F5 gene were discovered in proband 2. The 2238-9del AG in exon 13 introduced a premature termination code at 689 AA and the substitution of G6410 by T in exon 23 lead to the missense mutation Gly2079Val. Three F5 gene mutations, IVS8 -2A>G, 2238-9del AG and G6410T, have been identified in two Chinese pedigree with congenital FV deficiency, respectively.
OBJECTIVE: To discover the gene mutations of a pedigree with inherited factor V (FV) deficiency. METHODS: The activated partial thromboplastin time (APTT), prothrombin time (PT), FV activity (FV:C) and FV antigen test were adopted for phenotype diagnosis. The genomic DNA was extracted from the peripheral blood of the 16-year-old propositus, female. All the 25 exons and their flanks in the FV gene of the propositus were amplified by polymerase chain reaction (PCR). The PCR products were screened by direct sequencing and the mutations were further confirmed by restricted enzyme digestion. Six persons in the pedigree (grandfather, grandmother, father, mother, uncle, and aunt) were examined too. 108 healthy blood donors were used as controls. RESULTS: The APTT, PT, FV:C, and FV:Ag of the propositus were 126.6s, 42.8s, 0.3% and 1.3% respectively. The Fbg and FII, FVII, FVIII, FIX, FX activities were in normal range. FV:C of the members of the pedigree was 36% - 70%, and the FV:Ag of the pedigree members was 26.4% - 45.3% that of the mixture of 30 normal plasma samples. Taking the GeneBank Z99572 sequence as the reference, totally five variations in the FV gene were found in the propositus. The mutations, A1348G and 4887 approximately 8delG, were traced to her father and her mother respectively. No 1348G-->T mutation was found in the 108 controls. CONCLUSION: The FV deficiency of the propositus is caused by missense mutation of G1348T and frameshift mutation of 4887 approximately 8delG, which haven't been identified previously.
OBJECTIVE: To identify gene mutations of a pedigree with inherited factor V (FV) deficiency. METHODS: The activated partial thromboplastin time (APTT), prothrombin time (PT), FV activity (FV:C) and FV antigen (FV:Ag) tests were performed for phenotypic diagnosis. The genomic DNA was extracted from the peripheral blood of the proband and all the 25 exons and their flanks of FV gene were amplified by polymerase chain reaction (PCR). The PCR products were screened by direct sequencing and the mutations were further confirmed by restriction enzyme digestion. RESULTS: APTT, PT, TT, FV:C, FV:Ag of the proband were 249.2 s, 46.6 s, 17.9 s, 0.1% and 1.5%, respectively. FII, FVII, FVIII, FIX, FX activities, vWF and Fg were within normal ranges. Taking the GenBank Z99572 sequence as the reference, four mutations were identified in FV gene of the proband. They were a heterozygous two bases deletion in exon 13 (2238 approximately 2239delAG) introducing a frameshift and a premature stop at codon 689, and a heterozygous missense mutation in exon 23 (G6410T) resulting in the substitution of Gly for Val at codon 2079, respectively. The proband's father and mother were heterozygous for G6410T and for 2238 approximately 2239delAG, respectively. CONCLUSION: The severe FV deficiency of the proband is caused by a frameshift mutation of 2238 approximately 2239delAG and a missense mutation of G6410T, which haven't been identified before.
We report a thrombotic family with combined type I antithrombin deficiency and factor V Leiden (factor V-R506Q) in which the proposita, affected by recurrent venous and arterial thrombosis, was also characterized by mild hyperhomocysteinemia (28 micromol/l; normal <18.5 micromol/l). Her two thrombotic sisters, with normal antithrombin levels and factor V molecules, showed hyperhomocysteinemia (51 and 30 micromol/l, respectively). Four other members of the family had the combined antithrombin/factor V Leiden defect and two of them had thrombosis. The common A223V mutation in the methylenetetrahydrofolate reductase gene, responsible for the thermolabile variant of the enzyme, was found to be heterozygous in the proposita; the two sisters were homozygous and heterozygous, respectively. The heterozygous sister also had a high titre of antiphospholipid antibodies (85 units of immunoglobulin G antiphospholipid antibody/ml). Furthermore, low plasma folate levels were found in the three hyperhomocysteinemic subjects of the family. This family with several prothrombotic defects is a clear example of the polyfactorial nature of thrombophilia.
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A novel homozygous 3571C-->T nonsense mutation predicting the synthesis of a truncated factor V (FV) molecule was identified in exon 13 of the human coagulation factor V gene in two unrelated Italian probands with undetectable plasma levels of FV antigen and activity. Both patients were also homozygous for the FV Leiden mutation. Reverse transcription polymerase chain reaction studies showed strongly reduced mRNA levels of the mutant FV allele and FV heavy and light chains were not measurable in the plasma of the probands and reverse transcriptase. Haplotype analysis indicated that the nonsense mutation in both families had a common founder a long time ago.
Screening for a resistance against activated protein C (aPCR), which is in most cases caused by FV:Q506 mutation, is performed by functional tests measuring the effect of aPC on activated partial thromboplastin time (aPTT). Because of an insufficient discrimination between FV:Q506 mutation negative and positive individuals with the first generation of the functional test Coatest aPC Resistance (Chromogenix AB, Mölndal, Sweden), the definition of an arbitrary cut-off level was only possible using the results of DNA analysis. The use of an arbitrary cut-off level still resulted in unsatisfactory low sensitivity and specificity for the functional test. Thus, time- and cost-consuming DNA analyses had to be performed frequently to establish the diagnosis. The objective of this study was to evaluate an improved version of this assay that uses predilution of samples with factor V deficient plasma containing a heparin neutralizer. Using the data from 32 FV:Q506 mutation positive and 55 mutation negative individuals, the authors calculated a cut-off value resulting in an enhanced sensitivity (0.91 versus 1.0) and specificity (0.77 versus 1.0) compared to the old one. Imprecision was lowered from 5.36% (first generation) to 2.43%, in particular in samples with longer clotting times. In patients with prolonged aPTT, either caused by therapy with oral anticoagulants or heparin, correct results were obtained with the second generation assay, in contrast to the first generation assay. With this second generation assay the number of DNA analyses can be substantially reduced.
A male infant with severe bleeding tendency had undetectable factor V activity. Sequence analysis of the proband's DNA revealed one base deletion in exon 13 (2952delT) and one base insertion in exon 16 (5493insG) in heterozygous form. Both mutations introduced a frameshift and a premature stop at codons 930 and 1776, respectively. The proband's father and mother were heterozygous for 2952delT and for 5493insG, respectively. Both mutations would result in the synthesis of truncated proteins lacking complete light chain or its C-terminal part. In the patient's plasma, no factor V light chain was detected by enzyme-linked immunosorbent assay. The N-terminal portion of factor V containing the heavy chain, and the connecting B domain was severely reduced but detectable (1.7%). A small amount of truncated factor V-specific protein with a molecular weight ratio of 236 kd could be immunoprecipitated from the plasma and detected by Western blotting. This protein, factor V(Debrecen), corresponds to the translated product of exon 16 mutant allele.
UNLABELLED: We report an exceptional case of cutaneous necrosis due to the coexistence of 4 thrombophilic factors, inherited and acquired. We would like to draw attention to these unrecognized associations. CASE REPORT: A 72-year-old woman was admitted with a 5 month history of necrotic nonhealing, painful ulcer of both legs and recently a purple toe. She had a history of 3 deep venous thromboses of the leg complicated by pulmonary embolism. A skin biopsy of the ulcer and purple toe showed only thrombosis in the dermal vessel. Laboratory findings showed a circulating lupus anticoagulant, positive anticardiolipin antibodies, antinuclear antibodies (1/320 dilution) and an anti Sm. Moreover, activated protein C resistance associated with factor V Leiden mutation and hyperhomocysteinemia was found; protein S was transiently low. With iloprost, oral anticoagulant, vitamin B12 and folic acid, the evolution was good, with healing of ulcer. COMMENTS: cutaneous necrosis can reveal hypercoagulable states, sometimes complex. We find 4 thrombophilic factors in our case, i.e. antiphospholipid antibodies, factor V Leiden, protein S deficiency and hyperhomocysteinemia. This is exceptional but highlights the role of several constitutional and acquired thrombophilic factors in the genesis of thrombosis. Extended protein C pathway disturbances could explain the mechanism that leads to cutaneous necrosis, in this patient, with an antiphospholipid syndrome. This case shows that it is necessary in some circumstances to make a complete hemostatic laboratory search to detect several thrombophilic factors. If they are present they can justify an oral anticoagulant treatment and a familial screening.
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