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The article presents a case study of an Italian male patient, who experienced haemarthrosis only after trauma at the age of 18 years. It shows that the overall moderate reduction in coagulation factor activities would reflect a residual carboxylase activity. It expects the specific relationships between the vitamin K supplementation outcome and gene lesions. It suggests that a M174R alteration is capable of investigating the molecular bases of poor response of the mutated carboxylase.

The factors associated with persistent instability of oral anticoagulant treatment (OAT) were investigated in a case-control study. The most unstable patients from 35 Italian anticoagulation clinics were matched with stable controls, for gender, age and OAT indication. Socio-demographic data, medical history, dietary and life habits, cytochrome P450 CYP2C9 variants, blood cell count, liver and renal functions were investigated. An 'Abbreviated Mental Test' (AMT) and a questionnaire to assess patient compliance to, and comprehension of, OAT indications and mechanisms were administered. An International Normalized Ratio (INR) above 4.5 was more frequently found in cases (n = 77) than controls (n = 80) (12.3% vs. 0.4%; P < 0.0001). The odds ratio for instability was significantly higher for: people who worked versus pensioners, acenocoumarol versus warfarin, and an insufficient score in the AMT and/or in the questionnaire. Cytochrome P450 CYP2C9 variants *1/*3 or *2/*3 or *3/*3 were more frequent among cases than controls (29.9% vs.15.0%; P = 0.042). No differences were observed as regards the other variables. In conclusion, we found that high intra-individual variability in OAT control was multifactorial, but poor OAT comprehension was prevalent.

We investigated the role of frequent fibrinogen polymorphisms in venous thromboembolic disease in conjunction with inherited thrombophilia. Two hundred unrelated subjects, all carriers of the factor V R506Q mutation (FV Leiden), were genotyped at the fibrinogen gene cluster. Among these subjects, 100 had experienced previous venous thromboembolism (VTE) and 100 were still asymptomatic for VTE. Significant differences were observed between the groups for the BclI polymorphism (P = 0.004). Scanning, by sequencing the DNA regions flanking the BclI marker, revealed new polymorphisms, a C to T transition and a G to T transversion at 1520 and 3369 base pairs 3' to the beta gene stop codon respectively. These markers showed less association with the clinical phenotype than BclI itself. A combined genotype including 10 markers was more frequent among the asymptomatic subjects (17%) than among patients (3%), and was associated with a reduction in fibrinogen antigen level (2.42 +/- 0.35 vs 2.69 +/- 0.41 g/l, P = 0.028) among the asymptomatic subjects. Our data suggest that, in the presence of inherited thrombophilia, frequent fibrinogen polymorphisms may interact to modulate the risk of venous thromboembolism.

The role of factor V (FV) mutations in activated protein C (APC) resistance and FV deficiency is well established. We report on the identification of a highly polymorphic (AT)n microsatellite marker in the FV gene, which represents an informative tool for the investigation of the origin and evolution of pathologically relevant FV genetic components. A high number of different microsatellite alleles were found to be associated with FV R506Q and FV H1299R, two single-origin mutations. An example of the use of the microsatellite marker in family studies of thrombophilia and FV deficiency is also provided.

Two patients from two unrelated families with a history of thrombosis showed severe plasma activated protein C (APC) resistance. However, genotypic analysis demonstrated that the patients were heterozygous for factor V (FV) Leiden mutation. Coagulation studies revealed that FV clotting activity and antigen were similarly reduced at about 50% of normal in the patients. One brother of propositus A also showed the same abnormalities. Genetic analysis showed that, in addition to FV Leiden mutation in exon 10 of the FV gene (G1691A), these patients had a transition in exon 13 of the FV gene (A4070G; R2 allele) predicting His1299Arg substitution in the mature FV. Study by RT-PCR of platelet FV mRNA indicated that the mRNA produced by the FV gene, marked by the R2 allele, was reduced in amount in both pseudohomozygous patients of family A. The R2 allele has previously been demonstrated to be significantly associated with plasma FV deficiency in the Italian population. The presence of FV deficiency did not protect the propositi from thrombosis. These data confirm that genotypic analysis is mandatory in patients with phenotypic severe APC resistance before these patients are definitely classified as homozygotes for FV Leiden and that further genotypic analysis is advisable.

We studied a patient affected by von Willebrand disease type 2A who experienced several mild bleeding episodes and was characterized by markedly reduced haemostatic parameters. In the exon 28 of von Willebrand factor (vWF) gene a T to C transition at nucleotide 8680, resulting in the missense mutation Leu817Pro, was found in the heterozygous form in the patient and in two affected relatives. As suggested by the presence in platelets of a complete spectrum of vWF multimers as well as by the increased vWF antigen levels and improved haemostasis after DDAVP treatment, the mutation is compatible with normal multimerization, and could be responsible for a reduced stability or an impaired physiological secretion of vWF.

Resistance to activated protein C (APC) is at present considered the most frequent laboratory abnormality in patients with deep-vein thrombosis. An increased risk for venous thrombosis is associated to the use of oral contraceptives (OC). We studied APC sensitivity in 50 healthy women taking OC and in 50 healthy controls, matched for age, smoking habit, educational and social levels, and the main biochemical routinary parameters. Subjects with a personal or familial history of thrombosis and also with chronic or acute diseases were excluded. Protein C, protein S, antithrombin III and lupus anticoagulant activity (LAC) were also evaluated. Increased fibrinogen and protein C levels, decreased protein S. and shortened PT and APTT were also observed in women taking OC. APC sensitivity ratio (APC-SR) was significantly lower in the OC group than in a control group (2.6 +/- 0.38 v 2.81 +/- 0.35, P < 0.01). Seven of eight women with APC ratio < or = 2 (APC resistant) were OC users: the difference of prevalence was statistically significant (chi-squared test, P < 0.05). Only two out of eight women were found heterozygous for the Leiden factor V mutation. Two APC-resistant women without the Leiden mutation subsequently discontinued OC and both then normalized their APC-SR. We conclude that acquired factors, i.e. oral contraceptives, may play an important role in determining plasma APC resistance.

The presence of gene lesions in coagulation factor X (FX, Stuart factor) was investigated in asymptomatic subjects with FX deficiency characterized by the presence of dysfunctional molecules in plasma, as demonstrated by the discrepancy between clotting activity and antigen level. A missense mutation (Ser334Pro) in the catalytic domain was found in three unrelated families in both the homozygous and the heterozygous conditions, and also in the compound heterozygous form with the substitution of Lys for 102 Glu. None of the mutations was detected in 40 unrelated subjects from the same geographic area. The Ser334Pro mutation affects a serine protease region characterized by extensive variation in the coagulation factors but conserved in mammalian factor X molecules. The Glu102Lys mutation affects a residue of the second EGF-like module also conserved in protein C. Both mutated residues are surface-exposed and found in protein regions suggested to be involved in macromolecular interactions which are impaired in the dysfunctional molecules.