Factor 5 mutation profile in German patients with homozygous and heterozygous factor V deficiency

Summary.  Coagulation factor V (FV) plays an important role in the blood coagulation cascade as part of the prothrombinase complex. FV deficiency is a rare autosomal recessive bleeding disorder with variable phenotypic expression. Thus, our study reports 39 patients with FV deficiency. In 36 cases, we were able to identify a causative mutation. Of these, 20 patients were heterozygous for the identified mutation, nine were homozygous, six were compound heterozygous and one proband was pseudohomozygous. In the remaining patients, no mutation was found. A total of 42 genetic alterations (of which 33 were uniquely different mutations), comprising 19 missense mutations, eight nonsense mutations, four small deletions and two splice site mutations, were identified by this study. Twenty-three of these were novel sequence variations not previously described in the literature. Interestingly, all changes found in exon 13 resulted in null alleles as either nonsense mutations or small deletions. The overall profile of these new mutations corresponds well with the data published in the F5 database. In those cases, where data were available, information on FV activity levels and/or bleeding history is given. Interestingly, some patients with mild FV deficiency (FV:C about 50% of normal) also exhibited bleeding episodes. Our data substantially contribute to the broadening and better understanding of the FV deficiency mutational spectrum. Identifying the molecular basis of mutations underlying this rare coagulation disorder will allow more insight into the mechanisms involved in the variable clinical phenotypes of patients with FV deficiency.     

Methionine transamination in patients with homocystinuria due to cystathionine beta-synthase deficiency

To assess the ability of patients with homocystinuria due to cystathionine beta-synthase (CBS) deficiency to perform the reactions of the methionine transamination pathway, the concentrations of the products of this pathway were measured in plasma and urine. The results clearly demonstrate that CBS-deficient patients develop elevations of these metabolites once a threshold near 350 micromol/L for the concurrent plasma methionine concentration is exceeded. The absence of elevated methionine transamination products previously reported among 16 CBS-deficient B6-responsive patients may now be attributed to the fact that in those patients the plasma methionine concentrations were below this threshold. The observed elevations of transamination products were similar to those observed among patients with isolated hypermethioninemia. Plasma homocyst(e)ine did not exert a consistent effect on transamination metabolites, and betaine appeared to effect transamination chiefly by its tendency to elevate methionine. Even during betaine administration, the transamination pathway does not appear to be a quantitatively major route for the disposal of methionine.     

Factor V Leiden mutation in Sneddon syndrome

Sneddon syndrome (SNS) is characterized by the association of ischaemic cerebrovascular events and widespread livedo racemosa. Its pathophysiology is still controversial. The aim of this study was to evaluate the prevalence of factor V Leiden mutation in consecutive patients referred for SNS according to antiphospholipid antibodies (aPL) status. Fifty-three Caucasian patients were enrolled from 1996 to 2001. Diagnosis of SNS was based on the presence of a widespread livedo racemosa and at least one clinical neurologic ischaemic event. The following investigations were performed: detection of antithrombin III, protein C and protein S deficiency, lupus anticoagulant, anticardiolipin and anti-beta2 glycoprotein I antibodies, biologic false-positive test for syphilis, and factor V Leiden mutation by direct genomic analysis. Fisher's test and t-test were used for statistics. Detection of aPL on multiple determinations was negative in 31 patients (group 1) and positive in 22 patients (group 2). Factor V Leiden mutation was detected in six patients (11.3%), heterozygous in all. The frequency of this mutation was statistically higher in group 1 (6/31, 19.3%) than in group 2 (0/22; P = 0.035). Within aPL-negative SNS, the comparison of patients with versus without factor V Leiden mutation showed no difference for clinical data or familial history of thrombosis. A high prevalence of heterozygous factor V mutation was found in aPL-negative patients with SNS. This finding adds further arguments to consider SNS as a heterogeneous entity.     

Vascular presentation of cystathionine beta-synthase deficiency in adulthood

Several recent studies describing a solely vascular presentation of cystathionine beta-synthase (CBS) deficiency in adulthood prompted us to analyze the frequency of patients manifesting with vascular complications in the Czech Republic. Between 1980 and 2009, a total of 20 Czech patients with CBS deficiency have been diagnosed yielding an incidence of 1:311,000. These patients were divided into three groups based on symptoms leading to diagnosis: those with vascular complications, with connective tissue manifestation and with neurological presentation. A vascular event such as a clinical feature leading to diagnosis of homocystinuria was present in five patients, while two of them had no other symptoms typical for CBS deficiency at the time of diagnosis. All patients with the vascular manifestation were diagnosed only during the past decade. The median age of diagnosis was 29 years in the vascular, 11.5 years in the connective tissue and 4.5 years in the neurological group. The ratio of pyridoxine responsive to nonresponsive patients was higher in the vascular (4 of 5 patients) and connective tissue groups (6 of 7 patients) than in the neurological group (2 of 8 patients). Mutation c.833T>C (p.I278T) was frequent in patients with vascular (6/10 alleles) and connective tissue presentation (8/14 alleles), while it was not present in patients with neurological involvement (0/16 alleles). During the last decade, we have observed patients with homocystinuria diagnosed solely due to vascular events; this milder form of homocystinuria usually manifests at greater ages, has a high ratio of pyridoxine responsiveness/nonresponsiveness, and the mutation c.833T>C (p.I278T) is often present.     

Factor V Leiden mutation in cerebrovascular disease.

Several studies indicate a high prevalence of factor V Leiden mutation as the most frequent coagulation defect found in patients with venous thrombosis. The relationship between this mutation and cerebrovascular disease has not been established in adults. In this investigation, we studied 29 patients with ischemic stroke and 20 with intracerebral hemorrhage, all of whom were compared with 20 controls. A region of the factor V gene containing the Leiden mutation site was amplified with polymerase chain reaction and the presence of mutation was determined with restriction enzyme digestion. We found no evidence of an association between factor V Leiden mutation and ischemic stroke or intracerebral hemorrhage. There was no evidence of association in subgroup the analysis by age, smoking status, myocardial infarction, hypertension, diabetes mellitus, or coronary disease. Factor V Leiden mutation doesn't seem to be associated with a risk of cerebrovascular disease.     

Factor V Leiden, prothrombin G20210A, and protein C mutation frequency in Turkish venous thrombosis patients

Several inherited polymorphisms are associated with risk of venous thrombosis, including mutation at codon 506 of the factor V gene, mutation at position 20210 of the prothrombin gene, and mutations in the protein C gene. In this study, genotyping for factor V, prothrombin, and protein C mutations was performed in 50 patients and 25 control subjects by polymerase chain reaction-based analysis. The prevalence of factor V and prothrombin mutations was not significantly different from that in the general population. Nine of the patients had heterozygous protein C mutation. There was a high prevalence of the mutated protein C allele in the pulmonary emboli group (42.8%). Protein C mutation incidence was higher in the pulmonary emboli group than in the deep vein thrombosis (8.33%) and cerebral vein thrombosis (16.1%) groups. These results indicate that patients with protein C deficiency have a greater risk of thrombosis than patients with factor V or prothrombin G20210A mutation.     

Reproductive fitness in maternal homocystinuria due to cystathionine beta-synthase deficiency

Early diagnosis and improved treatment are leading to the potential for increased reproductive capability in homocystinuria due to cystathionine -synthase (CS) deficiency, but information about reproductive outcome and risk of thromboembolism in pregnancy is limited. To provide further information, clinical and biochemical information was obtained on women with maternal homocystinuria, on their pregnancies and on the offspring. This information included blood sulphur amino acids and total homocysteine, CS gene mutations and developmental and cognitive scores in the offspring. The study involved 15 pregnancies in 11 women, of whom 5 were pyridoxine-nonresponsive and 6 were pyridoxine-responsive. Complications of pregnancy included pre-eclampsia at term in two pregnancies and superficial venous thrombosis of the leg in a third pregnancy. One pregnancy was terminated and two pregnancies resulted in first-trimester spontaneous abortions. The remaining 12 pregnancies produced live-born infants with normal or above-normal birth measurements. One offspring has multiple congenital anomalies that include colobomas of the iris and choroid, neural tube defect and undescended testes. He is also mentally retarded and autistic. A second offspring has Beckwith–Wiedemann syndrome. The remaining 10 offspring were normal at birth and have remained normal. There was no relationship between the severity of the biochemical abnormalities or the therapies during pregnancy to either the pregnancy complications or the offspring outcomes. The infrequent occurrences of pregnancy complications, offspring abnormalities and maternal thromboembolic events in this series suggest that pregnancy and outcome in maternal homocystinuria are usually normal. Nevertheless, a cautious approach would include careful monitoring of these pregnancies with attention to metabolic therapy and possibly anticoagulation.     

Factor V Leiden mutation in venous thrombosis in southeast Turkey

Venous thrombosis (VT) is a common disease, with an annual incidence in the general population of approximately 1 per 1,000. Factor V Leiden mutation (G1691A) (FVL) is the most common risk factor in venous thrombosis. The prevalence of FVL for thrombosis varies greatly in different regions of the world. FVL mutation has been identified both by conventional method and fluorescence resonance energy transfer (FRET) with the LightCycler. Sixty-one patients with VT, different in age and sex, were consecutively entered into this study to assess the prevalence of FVL in VT in southeast Turkey. FVL mutation was found in 24.6% (15/61). Fourteen individuals were heterozygous and 1 homozygous, a rate of 22.9% and 1.6%, respectively. In conclusion, the authors suggest that FVL mutation is common in patients with venous thrombosis in southeast Turkey.     

Guidelines for the diagnosis and management of cystathionine beta-synthase deficiency

Cystathionine beta-synthase (CBS) deficiency is a rare inherited disorder in the methionine catabolic pathway, in which the impaired synthesis of cystathionine leads to accumulation of homocysteine. Patients can present to many different specialists and diagnosis is often delayed. Severely affected patients usually present in childhood with ectopia lentis, learning difficulties and skeletal abnormalities. These patients generally require treatment with a low-methionine diet and/or betaine. In contrast, mildly affected patients are likely to present as adults with thromboembolism and to respond to treatment with pyridoxine. In this article, we present recommendations for the diagnosis and management of CBS deficiency, based on a systematic review of the literature. Unfortunately, the quality of the evidence is poor, as it often is for rare diseases. We strongly recommend measuring the plasma total homocysteine concentrations in any patient whose clinical features suggest the diagnosis. Our recommendations may help to standardise testing for pyridoxine responsiveness. Current evidence suggests that patients are unlikely to develop complications if the plasma total homocysteine concentration is maintained below 120 μmol/L. Nevertheless, we recommend keeping the concentration below 100 μmol/L because levels fluctuate and the complications associated with high levels are so serious.     

Factor V Leiden,prothrombin gene mutation,and thrombosis risk in patients with antiphospholipid antibodies

OBJECTIVE: To determine if the prevalence of 2 prothrombotic genetic factors, factor V Leiden and prothrombin gene mutation, is increased in patients with antiphospholipid (aPL) antibodies with a history of venous/arterial thrombosis compared to patients with aPL antibodies with no history of thrombosis. METHODS: One hundred fifty-seven patients with aPL antibodies were studied. The occurrence of venous and arterial thrombotic events since the time of antibody detection was determined retrospectively, using appropriate clinical and diagnostic criteria. Clinical risk factors for thrombosis were documented and included hypertension, hyperlipidemia, cigarette smoking, diabetes, positive family history, use of oral contraceptive, pregnancy, trauma, hospitalization, varicose veins, and malignancy. Genomic DNA was extracted from blood cells for determination of factor V Leiden mutation G1691 --> A and prothrombin mutation G20210 --> A by polymerase chain reaction and restriction fragment length polymorphism analysis. RESULTS: Of 157 patients, 69 had a history of thrombosis (venous 37, arterial 32); 147 (94%) patients had anticardiolipin (aCL) antibodies; 69 (45%) had lupus anticoagulant (LAC). The prevalence of factor V Leiden in patients with thrombosis was 13% compared to 4.6% in patients without thrombosis (OR 3.11, CI 0.92-10.6). In patients with aCL antibodies, 15% of patients with arterial thrombosis had factor V mutation compared to 3.5% of patients without thrombosis (OR 4.9, CI 1.2-19.3). The prothrombin gene mutation was identified in 5 patients, none of whom had thrombosis. Stepwise logistic regression analysis indicated that LAC (p = 0.005), male sex (p = 0.04), and hypertension (p = 0.03) were the strongest risk factors for developing thrombosis and that no additional risk was conferred by factor V Leiden (p = 0.13) and prothrombin gene mutation. CONCLUSION: Although the prevalence of factor V Leiden is modestly increased in patients with autoimmune aPL antibodies and thrombosis, these results suggest that its detection does not significantly increase the risk of a thrombotic event, once other clinical risk factors have been considered. Prothrombin gene mutation is not associated with thrombosis in patients with aPL antibodies.     

Factor V Leiden mutation and type 1 diabetes mellitus.

Diabetes mellitus is considered to cause a tendency for arterial thrombosis. Recent studies addressed the association between venous and arterial disease. Resistance to activated protein C is one of the most common causes of venous thrombosis and linked to a single point mutation in the factor V gene, designated as factor V Leiden mutation. There is little information regarding the status of factor V Leiden mutation in type 1 diabetes. The aim of this study is to evaluate association among activated protein C sensitivity ratio, factor V Leiden mutation, and type 1 diabetes taking into account metabolic control, lipids and diabetic complications. The study population consisted of 47 healthy subjects (27.9 +/- 1.2 years) and 48 type 1 diabetic patients (27.9 +/- 1.1 years). Activated protein C sensitivity ratio was measured by activated partial thromboplastin time based assay. The presence of factor V Leiden mutation was determined by amplifying the fragments encompassing gene mutation by PCR. Mean normalized activated protein C sensitivity ratio values and prevalence of heterozygous factor V Leiden mutation were not significantly different between groups (1.08 +/- 0.03 and 6.3% in healthy subjects; 1.01 +/- 0.03 and 6.4% in type 1 diabetic patients, respectively). The activated protein C sensitivity ratio and factor V Leiden mutation were not found to be linked with metabolic control parameters, lipids and diabetic complications in type 1 diabetic patients. There was no association among factor V Leiden mutation, activated protein C sensitivity ratio and type 1 diabetes, metabolic control parameters as well as complications of diabetes. Although the propensity to thrombosis is increased in individuals with type 1 diabetes, activated protein C sensitivity ratio and factor V Leiden mutation do not appear to be significant determinants.