A novel two base pair deletion in the factor V gene associated with severe factor V deficiency

We studied a family in which the proband, a 13-year-old boy, had unmeasurable plasma levels of coagulation factor V antigen and activity. Clinical symptoms were severe, with several episodes of haemorrhages in the mucosal tracts (gastrointestinal, nose and urinary) and recurrent haemarthroses that caused permanent arthropathy. Sequence analysis of the factor V gene demonstrated the presence of a novel 2 base pair (bp) homozygous deletion in exon 13 at positions 2833-2834. This mutation, present in the heterozygous state in the asymptomatic mother and absent in the healthy brother, introduced a frameshift and a premature stop at codon 900. This would predict the synthesis of a truncated factor V molecule, lacking part of the B domain and the complete light chain. Because of the existence of a surveillance mechanism that selectively recognizes and degrades mRNA molecules carrying premature termination codons, we analysed the relative abundance of mutant vs. wild-type mRNA molecules in the platelets of the heterozygous proband's mother. The mutant mRNA was significantly reduced in amount (mutant/wild-type ratio 0.35). This is the first reported mutation in the factor V gene causing severe factor V deficiency, the effect of which was quantitatively analysed at mRNA level.

Factor V Leiden and antiphospholipid antibodies are significant risk factors for ischemic stroke in children

BACKGROUND AND PURPOSE

The association between ischemic childhood stroke and thrombophilia has been debated. We studied the prevalence of thrombophilia risk factors in 65 unrelated children with ischemic stroke compared with 145 control subjects.

METHODS

Patients and control subjects were tested for antithrombin protein C and protein S deficiencies, the presence of antiphospholipid antibodies (APLA), factor V Leiden (FVL), G20210A polymorphism of factor II gene (FII G20210A), and C677T polymorphism of 5,10-methylenetetrahydrofolate reductase gene (C677T MTHFR).

RESULTS

Of 65 children, 7 had a stroke in the neonatal/perinatal period and therefore were analyzed separately. Thirty-one of the remaining 58 patients with pediatric stroke (53.4%) were found to have at least 1 thrombophilia marker compared with only 25.5% of control subjects. None of the patients or control subjects had protein S or antithrombin III deficiency. The prevalence of protein C deficiency was higher among pediatric stroke patients than among control subjects, but the difference was not statistically significant (OR=7, 95% CI 0.75 to 65.1). Heterozygous FII G20210A and homozygous MTHFR 677T were not associated with an increased risk for stroke (OR=1.29, 95% CI 0.2 to 8.2; and OR=1.06, 95% CI 0.4 to 2.7, respectively). In contrast, the presence of APLA was associated with a >6-fold risk of stroke (OR=6. 08, 95% CI 1.5 to 24.3), and the heterozygosity for FVL increased the risk of stroke by almost 5-fold (OR=4.82, 95% CI 1.4 to 16.5). Five patients with pediatric stroke had a combination of > or =2 thrombophilia markers, whereas none of the control subjects had a combination of the markers. Most of the patients with neonatal/perinatal stroke were found to have at least 1 thrombophilia marker.

CONCLUSIONS

These data suggest that the prevalence of thrombophilia markers is increased in children with stroke compared with control subjects and, specifically, that FVL and APLA contribute significantly to stroke occurrence.

Sudden infant death syndrome, childhood thrombosis, and presence of genetic risk factors for thrombosis

Sudden infant death syndrome or "cot death" has until the late eighties been a significant cause of death in children between the ages of 1 month and 1 year. Approximately two per 1000 children born alive dies of sudden infant death syndrome each year in Western Europe, North America, and Australia. The vulnerability of the infant brain stem to ischemia has been suggested to be a conceivable cause of sudden infant death syndrome. This is compatible with a hypothesis that genetic risk factors for cerebral thrombosis could cause microinfarction in the brain stem during the first month of life, affecting vital centers or their blood supply. The presence of three common point mutations seen in families with thrombophilia (1691G-->A in the coagulation factor V gene, 677C-->T in the methylenetetrahydrofolate reductase gene, and the 20210G-->A mutation in the prothrombin gene) could increase the risk for thrombosis in the child. This prompted us to investigate these genetic markers of thromboembolic disease in 121 cases of sudden infant death syndrome and in relevant controls, in the expectation of a more frequent occurrence of these markers if thrombosis is an etiological factor in sudden infant death syndrome. The frequency of homozygous 1691G-->A mutation in SIDS cases was higher than expected (odds ratio: 7.3, 95% confidence interval, 1.2-45.8). The allele frequencies (theta;) in cases of sudden infant death syndrome of the 1691G-->A, 677C-->T, and 20210G-->A alleles was 2.6% (1.0-5.5), 32.6% (26.8-38.9), and 0.9% (0.1-3.4), respectively. None of the allele frequencies found in the background population (3.4% for the 1691G-->A allele, 29% for the 677C-->T allele, and 1% for the 20210G-->A allele) differed significantly from that in cases of sudden infant death syndrome. In 5,251,027 inhabitants in Denmark, the incidence of venous thromboembolism was 0.9 per 1000 per year in the background population, and less than one-thousandth of these were children. Consequently it is not likely that venous thrombosis is a major cause of sudden infant death syndrome. On the other hand, this does not exclude other known or unknown risk factors for thrombosis as possible etiological factors for sudden infant death syndrome. It is likely that we must continuously employ the exclusion principle on possible etiological causes in genetic material from a large group of victims of sudden infant death syndrome if the phenomenon of sudden infant death syndrome is to be ascribed to a specific hereditary disorder.

Postoperative stroke in a child with cerebral palsy heterozygous for factor V Leiden

A 5-year-old with spastic quadraparetic cerebral palsy suffered multiple strokes after extensive orthopedic surgery. Coagulation testing was undertaken to determine whether a familial thrombophilia was present. The patient was found to be heterozygous for factor V Leiden. Factor V Leiden may be a risk factor for central nervous system events in special-needs children, particularly when common medical conditions create additional procoagulant risks.

Rescue of fatal neonatal hemorrhage in factor V deficient mice by low level transgene expression

Factor V (FV) is a critical component of the coagulation cascade. FV-deficient patients suffer moderate to severe bleeding, though residual FV activity is detectable in nearly all cases. In contrast, FV-deficient mice die either during mid-embryogenesis, or of massive perinatal hemorrhage. In order to examine the requirements for FV in murine embryogenesis and hemostasis, we generated transgenic mouse lines expressing a Fv minigene under control of either the tissue-specific albumin (Malb) or rat platelet factor 4 (Rpf4) promoter. A total of 12 Malb and 3 Rpf4 lines were analyzed. Though expression in the target tissue was detectable in most lines by RT-PCR, only low levels of transgene expression were achieved (<3% of endogenous Fv in all lines). Despite a low level of Fv transgene expression, rescue of the lethal Fv-/- phenotype was observed with one of the Malb transgenic (Tg+) lines. However, rescue appeared to be incomplete with continued loss of >1/2 of expected Tg+,Fv-/- mice in early embryogenesis. Rescued Tg+,Fv-/- mice have undetectable FV (<0.1%) in both plasma and platelet compartments, but survive the perinatal period and mature to adulthood without spontaneous hemorrhage. We conclude that FV present at <0.1% is sufficient to support postnatal survival. Failure of the Malb transgene to rescue the midembryonic block suggests that FV expression is required during mammalian development at higher levels or with a different tissue-specific or temporal pattern. Taken together, these data may explain the observation of residual FV activity in most human FV-deficient patients due to early embryonic lethality in those absolutely deficient, and suggest that minimal levels of FV expression, below the level of detection, also may be sufficient to support survival in humans.

Spectrum of hereditary coagulation factor deficiencies in eastern province, Saudi Arabia

In a 7-year retrospective analysis (1991-97) of the records of the Department of Haematology, Regional Laboratory and Blood Bank (Dammam), 54 patients from all parts of Saudi Arabia's Eastern Province were diagnosed with hereditary coagulation factor deficiencies. The largest group of patients, 42 haemophiliacs, included 4 non-Saudi patients. There were 39 haemophilia A or factor VIII deficiency patients, 2 haemophilia B or factor IX deficiency patients and 1 combined factor VIII and V deficiency patient. There were 5 Saudi patients with probable factor XIII deficiency, and 7 patients, all but one who were Saudi, had von Willebrand disease. The distribution of haemophilia patients in Eastern Province showed some differences compared with those reported from Riyadh and from Western countries. Among Saudis in Eastern Province, the number with suspected factor XIII deficiency, although low, was higher than that reported for other regions. The number of patients with haemophilia B and von Willebrand disease was lower than expected, when compared with the number of haemophilia A cases.

Gene-gene and gene-environment interactions determine risk of thrombosis in families with inherited antithrombin deficiency

To analyze inherited antithrombin deficiency as a risk factor for venous thromboembolism in various conditions with regard to the presence or absence of additional genetic or acquired risk factors, we compared 48 antithrombin-deficient individuals with 44 nondeficient individuals of 14 selected families with inherited antithrombin deficiency. The incidence of venous thromboembolism for antithrombin deficient individuals was 20 times higher than among nondeficient individuals (1.1% v 0.05% per year). At the age of 50 years, greater than 50% of antithrombin-deficient individuals had experienced thrombosis compared with 5% of nondeficient individuals. Additional genetic risk factors, Factor V Leiden and PT20210A, were found in more than half of these selected families. The effect of exposure to 2 genetic defects was a 5-fold increased incidence (4.6% per year; 95% confidence interval [CI], 1.9% to 11.1%). Acquired risk factors were often present, determining the onset of thrombosis. The incidence among those with exposure to antithrombin deficiency and an acquired risk factor was increased 20-fold (20.3% per year; 95% CI, 12.0% to 34.3%). In conclusion, in these thrombophilia families, the genetic and environmental factors interact to bring about venous thrombosis. Inherited antithrombin deficiency proves to be a prominent risk factor for venous thromboembolism. The increased risks among those with exposure to acquired risk factors should be considered and adequate prophylactic anticoagulant therapy in high-risk situations seems indicated in selected families with inherited antithrombin deficiency.

Familial association of hypoplasminogenemia and heterozygous factor V deficiency

The coinheritance of hypoplasminogenemia and heterozygous factor V deficiency in a relative with thrombotic disease and no hemorrhagic tendency is described. The proposita, a 28-year-old woman, suffered from neurologic disturbances due to two ischemic cerebral lesions confirmed by nuclear magnetic resonance scan. She was found to be affected with heterozygous plasminogen deficiency in a coagulation study for inherited thrombophilia. Moreover, she disclosed a prolongation of prothrombin time and activated partial thromboplastin time, which was compatible with heterozygous factor V deficiency. Her father, with a history of deep vein thrombosis, was also affected with plasminogen deficiency, as well as three brothers and one sister who were asymptomatic. The mother of the proposita showed borderline or slightly decreased factor V levels and normal plasminogen levels; she was therefore considered to be heterozygous for factor V deficiency. Heterozygous factor V deficiency was also found in one brother and one sister of the proposita, and they were both asymptomatic. Among the other available family members, one brother and one sister of the proposita, all asymptomatic for either thrombotic or bleeding events, showed a normal clotting and fibrinolytic profile. To our knowledge, this is the first case of combined heterozygous plasminogen and factor V deficiency in the same family. Two of six patients with hypoplasminogenemia showed thrombotic events, and in one of these symptomatic cases the coexistence of factor V deficiency did not prevent the occurrence of thrombosis. As expected, no hemorrhagic tendency was observed in patients with heterozygous factor V deficiency, who may be mildly symptomatic only in 10% of cases.

Familial coagulation factor V deficiency caused by a novel 4 base pair insertion in the factor V gene: factor V Stanford

An index patient with pseudohomozygosity for factor V Leiden was identified. Each of his two children inherited a different paternal factor V allele; a daughter was heterozygous for factor V Leiden, with 100% factor V activity, and a son was heterozygous for factor V deficiency, with 50% factor V activity. Genomic DNA was obtained from family members, and the 25 factor V exons and flanking intronic regions were sequenced in the proband and confirmed in the children. Within exon 13 of factor V, a 4 base insertion was found at NT 2856 in the proband and son. but not the daughter. This mutation, here designated factor V Stanford, results in a frameshift with loss of a thrombin activation site (R1545V) and premature termination of translation at amino acid 1560.

Development of a simple multiplex polymerase chain reaction for the simultaneous detection of factor V Leiden and prothrombin 20210A mutations

BACKGROUND

The demand for thrombophilia testing at the molecular level is increasing, and consequently, the work load of the routine molecular laboratory is also increasing. Efforts to lighten the work load, economize on time, and strive for reduced costs while still maintaining quality assurance are thus necessary.

METHODS AND RESULTS

A multiplex polymerase chain reaction (PCR) for the detection of factor V Leiden and prothrombin 20210A mutations was designed that enables the use of the same inexpensive restriction enzyme, controls for the digestion, and produces easily interpretable results.

CONCLUSION

The use of this new multiplex PCR and digestion analysis enabled us to simultaneously perform a routine screen for factor V Leiden and prothrombin 20210A mutations.

Pseudohomozygosity for activated protein C resistance is a risk factor for venous thrombosis

Pseudohomozygosity for activated protein C resistance (APC-r) is a rare condition due to the association of heterozygous FV Leiden mutation and partial type I FV deficiency. To assess the risk of venous thromboembolism in these subjects, seven families including 11 pseudohomozygotes and 45 relatives were examined. Among the relatives, 16 were heterozygous FV Leiden carriers, nine showed partial FV deficiency and 20 no abnormalities. Deep vein thrombosis occurred in 4/11 (36.3%) pseudohomozygous patients versus 6/16 (37. 4%) FV Leiden carriers and 1/20 (5%) normal relatives. Pseudohomozygotes and FV Leiden carriers had a significantly increased risk of venous thrombosis in comparison to normal relatives (RR 8.8 and 5.7, respectively). There was no difference between the thrombotic risk of pseudohomozygous subjects and of FV Leiden carriers (RR 1.6, 95% CI 0.43-5.7). Furthermore, there was no difference in thrombosis-free survival between pseudohomozygotes and 45 consecutive FV Leiden heterozygous outpatients, suggesting that a referral bias may explain the apparent younger age of thrombosis in the pseudohomozygotes in comparison to relatives with FV Leiden heterozygosity (27 years v 54 years; P = 0.01). Pseudohomozygosity for APC resistance carries a significantly higher risk for venous thromboembolism in comparison to normal subjects, but probably not in comparison to heterozygous FV Leiden carriers.

Molecular analysis of the ERGIC-53 gene in 35 families with combined factor V-factor VIII deficiency

Combined factor V-factor VIII deficiency (F5F8D) is a rare, autosomal recessive coagulation disorder in which the levels of both coagulation factors V and VIII are diminished. The F5F8D locus was previously mapped to a 1-cM interval on chromosome 18q21. Mutations in a candidate gene in this region, ERGIC-53, were recently found to be associated with the coagulation defect in nine Jewish families. We performed single-strand conformation and sequence analysis of the ERGIC-53 gene in 35 F5F8D families of different ethnic origins. We identified 13 distinct mutations accounting for 52 of 70 mutant alleles. These were 3 splice site mutations, 6 insertions and deletions resulting in translational frameshifts, 3 nonsense codons, and elimination of the translation initiation codon. These mutations are predicted to result in synthesis of either a truncated protein product or no protein at all. This study revealed that F5F8D shows extensive allelic heterogeneity and all ERGIC-53 mutations resulting in F5F8D are "null." Approximately 26% of the mutations have not been identified, suggesting that lesions in regulatory elements or severe abnormalities within the introns may be responsible for the disease in these individuals. In two such families, ERGIC-53 protein was detectable at normal levels in patients' lymphocytes, raising the further possibility of defects at other genetic loci.

ERGIC-53 gene structure and mutation analysis in 19 combined factors V and VIII deficiency families

Combined factors V and VIII deficiency is an autosomal recessive bleeding disorder associated with plasma levels of coagulation factors V and VIII approximately 5% to 30% of normal. The disease gene was recently identified as the endoplasmic reticulum-Golgi intermediate compartment protein ERGIC-53 by positional cloning, with the detection of two founder mutations in 10 Jewish families. To identify mutations in additional families, the structure of the ERGIC-53 gene was determined by genomic polymerase chain reaction (PCR) and sequence analysis of bacterial artificial chromosome clones containing the ERGIC-53 gene. Nineteen additional families were analyzed by direct sequence analysis of the entire coding region and the intron/exon junctions. Seven novel mutations were identified in 10 families, with one additional family found to harbor one of the two previously described mutations. All of the identified mutations would be predicted to result in complete absence of functional ERGIC-53 protein. In 8 of 19 families, no mutation was identified. Genotyping data indicate that at least two of these families are not linked to the ERGIC-53 locus. Taken together, these results suggest that a significant subset of combined factors V and VIII deficiency is due to mutation in one or more additional genes.

Combined factor V and factor VII deficiency due to an independent segregation of the two defects

A patient with combined factor V and factor VII deficiency is described together with a family study. The propositus appeared to be double heterozygous for factor V and factor VII deficiency. Since the patient showed a parallel decrease of activity and antigen, he appeared to be double heterozygous for a true deficiency. The patient had inherited the factor V defect from the mother and the factor VII defect from the father. The parents of the propositus were not consanguineous. Other family members were found to have isolated factor V or factor VII deficiency. This is the third family so far described with this peculiar combined defect but the first to be investigated by clotting and immunologic assays.

[The concomitant presence of prohemorrhagic and thrombophilic changes in coagulation factor V: a severe defect of coagulant activity and homozygote resistance to activated protein C]

We describe the peculiar and concomitant presence of a severe coagulation defect predisposing to bleeding and a mutation associated with inherited thrombophilia. A 6-year-old boy had a severe deficiency in factor V procoagulant activity and antigen and yet remained asymptomatic. This paradox might be explained by the hypothesis of the simultaneous presence of a thrombophilic disorder that might have restored hemostatic balance. The boy was a homozygous carrier of the Arg506Gln mutation of coagulation factor V, that renders this factor resistant to inactivation by its naturally occurring inhibitor, activated protein C. The family members, none of whom had bleeding or thrombotic symptoms, were heterozygotes for either the bleeding or the thrombophilic defect. Despite the severity of the bleeding defect, the absence of bleeding symptoms in the boy can be explained by the hypothesis that any residual amount of factor V present in his plasma is resistant to inactivation by activated protein C.

The factor V gene A4070G mutation and the risk of venous thrombosis

The A4070G polymorphism in exon 13 of the factor V (FV) gene, which replaces His by Arg at position 1299 of the B domain, was recently shown to influence circulating FV levels and to contribute to the activated protein C (APC) resistance phenotype. We examined the impact of this polymorphism in a population of unselected patients with venous thromboembolic disease (VTE). The prevalence of the G4070 (R2) allele was determined in 205 patients and 394 healthy subjects of similar age and sex distribution. Thirty-seven patients (18%) were heterozygous for the R2 allele and 1 (0.5%) was homozygous. Forty-four controls (11.2%) were heterozygous for the R2 allele and 1 (0.2%) was homozygous. Thus, the allelic frequency was significantly higher in the patients with VTE than in the healthy controls, with respective values of 9.5% and 5.8%. The odds ratio was 1.8 (95% CI: 1.1-2.8, p = 0.02), pointing to an increased risk of VTE in carriers of the R2 allele. After excluding subjects with putative or confirmed gene defects (mainly the FV R506Q mutation), the R2 allele was still a risk factor for VTE in the remaining patients, with an odds ratio of 2.0 (95% CI: 1.2-3.5, p = 0.01), demonstrating that this polymorphism is itself a risk factor. This study also confirms that the R2 allele influences APC resistance (APCR) in the absence of the FV R506Q mutation.

The factor II G20210A and factor V G1691A gene transitions and coronary heart disease

BACKGROUND

G to A transitions at nucleotide position 20210 of the factor II (Fll) gene and at 1691 of the factor V (FV) gene have been shown to be associated with an increased risk of venous thrombosis. Since it is still unclear whether both gene variations are also related to an increased risk of coronary heart disease (CHD), we studied the relation of both gene variations to coronary artery disease (CAD) and myocardial infarction (MI) in a sample of 2210 male individuals whose coronary anatomy were defined by coronary angiography.

RESULTS

In the total sample, the FII G20210A gene variation was not associated with the presence or the extent of CAD, the latter defined either by the degree of vessel disease or by a CHD score according to Gensini. However, individuals with unfavourable lipid profiles showed pronounced differences in CHD scores between GA heterozygotes and GG homozygotes: this observation applied in particular to younger patients (<62 years; mean age of total sample) who simultaneously had low apoAI/apoB ratios (< 1.19, mean value) and high Lp(a) plasma levels (>28 mg/dl; mean value). In addition, in subjects without acetylsalicylic acid treatment GA heterozygotes had clearly higher CHD scores than AA genotypes. Further restriction to smokers, to subjects with high fibrinogen plasma levels (>3.47 g/l; mean value) or to patients with high glucose concentrations (>112 mg/dl; mean value) tended to increase the difference in CHD score between FII G20210A genotypes. An association of the FII G20210A gene variation with non-fatal MI was not observed. In the total sample and in high and low risk subpopulations, an association of the FV G1691A gene variation was not detected neither with presence and extent of CAD or with nonfatal MI.

CONCLUSION

The importance of the factor II G20210A gene variation for CHD may be restricted to individuals with major cardiovascular risk factors. In addition, the present study did not strengthen the hypothesis of the factor V G 1691 A transition as a risk factor of coronary heart disease neither in the total sample nor in subgroups of individuals who were at high or low risk of CHD.

Thrombophilia as a multigenic disease

BACKGROUND AND OBJECTIVE

Venous thrombosis is a common disease annually affecting 1 in 1000 individuals. The multifactorial nature of the disease is illustrated by the frequent identification of one or more predisposing genetic and/or environmental risk factors in thrombosis patients. Most of the genetic defects known today affect the function of the natural anticoagulant pathways and in particular the protein C system. This presentation focuses on the importance of the genetic factors in the pathogenesis of inherited thrombophilia with particular emphasis on those defects which affect the protein C system.

INFORMATION SOURCES

Published results in articles covered by the Medline database have been integrated with our original studies in the field of thrombophilia.

STATE OF THE ART AND PERSPECTIVES

The risk of venous thrombosis is increased when the hemostatic balance between pro- and anti-coagulant forces is shifted in favor of coagulation. When this is caused by an inherited defect, the resulting hypercoagulable state is a lifelong risk factor for thrombosis. Resistance to activated protein C (APC resistance) is the most common inherited hypercoagulable state found to be associated with venous thrombosis. It is caused by a single point mutation in the factor V (FV) gene, which predicts the substitution of Arg506 with a Gln. Arg506 is one of three APC-cleavage sites and the mutation results in the loss of this APC-cleavage site. The mutation is only found in Caucasians but the prevalence of the mutant FV allele (FV:Q506) varies between countries. It is found to be highly prevalent (up to 15%) in Scandinavian populations, in areas with high incidence of thrombosis. FV:Q506 is associated with a 5-10-fold increased risk of thrombosis and is found in 20-60% of Caucasian patients with thrombosis. The second most common inherited risk factor for thrombosis is a point mutation (G20210A) in the 3' untranslated region of the prothrombin gene. This mutation is present in approximately 2% of healthy individuals and in 6-7% of thrombosis patients, suggesting it to be a mild risk factor of thrombosis. Other less common genetic risk factors for thrombosis are the deficiencies of natural anticoagulant proteins such as antithrombin, protein C or protein S. Such defects are present in less than 1% of healthy individuals and together they account for 5-10% of genetic defects found in patients with venous thrombosis. Owing to the high prevalence of inherited APC resistance (FV:Q506) and of the G20210A mutation in the prothrombin gene, combinations of genetic defects are relatively common in the general population. As each genetic defect is an independent risk factor for thrombosis, individuals with multiple defects have a highly increased risk of thrombosis. As a consequence, multiple defects are often found in patients with thrombosis.

Careful selection of sample dilution and factor-V-deficient plasma makes the modified activated protein C resistance test highly specific for the factor V Leiden mutation

The aim of this study was to evaluate critically the recently modified activated-partial-thromboplastin-time (APTT)-based activated protein C (APC)-resistance tests, which are more specific for the factor V Leiden mutation than the first generation APC-resistance tests. The only modification to these tests is the predilution of the plasma sample in factor-V-deficient plasma. The intended effect of this predilution is to bring the concentrations of all clotting factors, except factor V, to the same normal levels. This, in principle, makes the tests also suitable for assaying the plasma of patients treated with oral anticoagulants and heparin, or of patients with a lupus anticoagulant. However, not every factor-V-deficient plasma is suitable for this application. Because the factor V:factor VIII ratio is important in establishing the APC ratio, the factor-V-deficient plasma should contain a sufficiently high factor VIII concentration. We also found that the optimal dilution to obtain the same APC ratios for patients, whether or not treated with coumarins or heparin, is not the same for each test or factor-V-deficient plasma. We compared two modified APTT-based APC-resistance tests (one developed in our laboratory and one commercial) with respect to their ability to discriminate between carriers and non-carriers of the factor V Leiden mutation. Both modified tests gave complete separation of carriers and non-carriers of the factor V Leiden mutation whether or not they are treated with anticoagulants. This makes these tests very suitable for routine screening.

Symptoms of inherited factor V deficiency in 35 Iranian patients

The type of bleeding symptom has been evaluated in 35 Iranian patients with an inherited deficiency of factor V, with plasma levels between 1% and 10%. The most frequent symptoms included epistaxis and excessive bleeding after surgery. Haemarthroses and muscle haematomas were less common, even in severely deficient patients. More severe symptoms such as gastrointestinal and central nervous system bleeding were rare. The severity of bleeding symptoms was only partially related to the degree of factor V deficiency in plasma. On the whole, human factor V deficiency is characterized by a moderately severe bleeding phenotype.

Wilson's disease with concomitant beta thalassaemia and factor V deficiency

A case of late presentation of Wilson's disease in a female with a thalassaemic trait is reported in whom diagnosis of Factor V deficiency was made. Despite ignoring the disease for years the patient had compensated cirrhosis. She had a dramatic family history of Wilson's disease affecting at least two brothers and two sisters. Moreover, her haematologic problems were not clinically revealed until diagnosis had been made on the basis of suspicions arising from laboratory results. The therapy of choice for hepatolenticular degeneration was not feasible due to the patient's refusal. Zinc salts were, therefore, administered. To our knowledge the association of such rare genetic disorders has not been reported.