Role of family history of venous thromboembolism and thrombophilia as predictors of recurrence: a prospective follow-up study

BACKGROUND

Several studies have shown that the family history of venous thromboembolism (FHVTE) is a predictor of first venous thromboembolism (VTE). However its role in recurrent VTE is still controversial.

OBJECTIVES

To investigate whether the presence of FHVTE is a risk factor for VTE recurrence in patients from a well-characterized Malmö thrombophilia study.

METHODS

VTE patients from the Malmö Thrombophilia Study were followed from discontinuation of warfarin treatment until diagnosis of VTE recurrence or to the end of the study (maximum follow-up 9.8 years).

RESULTS

There were 127 events of VTE recurrence (12.2%) registered during the follow-up. Multivariate Cox regression analysis in patients with unprovoked first VTE showed that FHVTE was associated with higher risk of VTE recurrence (hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.2-2.9) compared with patients with no FHVTE. Stratification of data according to thrombophilia status of patients showed that compared with the reference group (no FHVTE or thrombophilia), thrombophilia together with FHVTE was associated with a higher risk of VTE recurrence (HR 3.2, 95% CI 1.8-5.9) than thrombophilia alone (HR 1.8, 95% CI 1.02-3.2) independent of DVT location and duration of warfarin treatment. FHVTE was mainly an important risk factor of VTE recurrence in women (HR 3.1, 95% CI 1.6-5.8) but not in men (HR 1.1, 95% CI 0.6-2.2).

CONCLUSION

Our results show that FHVTE is a risk factor for VTE recurrence in patients who had unprovoked first VTE. Furthermore, presence of FHVTE may be an additional risk factor of VTE recurrence in thrombophilia-positive patients.

The association between apolipoprotein M and insulin resistance varies with country of birth

BACKGROUND AND AIMS

Risk of type 2 diabetes mellitus (T2DM) differs according to ethnicity. Levels of apolipoprotein M (ApoM) have been shown to be decreased in T2DM. However, its role in different ethnicities is not known. We examined the differences in plasma ApoM levels in Swedish residents born in Iraq (Iraqis) and Sweden (Swedes) in relation to T2DM and insulin resistance (IR).

METHODS AND RESULTS

Iraqis and Swedes, aged 45-65 years residing in Rosengård area of Malmö were randomly selected from census records and underwent an oral glucose tolerance test. Plasma levels of ApoM were quantified in 162 participants (Iraqis, n = 91; Swedes, n = 71) by a sandwich ELISA method. Age-, sex-, and body mass index (BMI) adjusted plasma ApoM levels differed by country of birth, with Swedes having 18% higher levels compared to Iraqis (p = 0.001). ApoM levels (mean ± SD) were significantly decreased in Swedes with T2DM (0.73 ± 0.18) compared to those with normal glucose tolerance (NGT) (0.89 ± 0.24; p = 0.03). By contrast, no significant difference in ApoM levels was found between Iraqis with T2DM (0.70 ± 0.17) and those with NGT (0.73 ± 0.13; p = 0.41). In multivariate linear regression analysis with an interaction term between IR and country of birth, low ApoM levels remained significantly associated with IR in Swedes (p = 0.008), independently of age, sex, BMI, family history of diabetes, HDL, LDL, and triglycerides, but not in Iraqis (p = 0.35).

CONCLUSION

Our results show that ApoM levels differ according to country of birth and are associated with IR and T2DM only in Swedes.

Mothers, places and risk of hospitalization for childhood asthma: a nationwide study from Sweden: epidemiology of allergic disease

OBJECTIVE

This study examines whether neighbourhood deprivation increases the risk of hospitalization for childhood asthma, after accounting for individual-level maternal socio-demographic characteristics.

DESIGN

An open cohort of all singleton children aged 2-11 years was followed between January 1, 1995 and December 31, 2006. Childhood residential addresses were geocoded and classified according to the level of neighbourhood deprivation. Data were analysed by multilevel logistic regression, with individual-level characteristics (sex, age, maternal marital status, family income, maternal educational attainment, maternal immigration status, maternal urban/rural status, mobility, maternal asthma history and maternal smoking) at the first level and level of neighbourhood deprivation at the second level.

RESULTS

During the study period, among a total of 866,860 children, 17,682 (2.0%) were hospitalized with childhood asthma. Age-adjusted hospital rates for childhood asthma increased with increasing level of neighbourhood deprivation. In the study population, 1.9% and 2.3% of children in the least and most deprived neighbourhoods, respectively, were affected by childhood asthma. Hospital rates of childhood asthma increased with increasing neighbourhood-level deprivation across all individual-level maternal socio-demographic categories, including marital status, educational attainment, urban/rural status, maternal history of asthma and smoking. The odds ratio (OR) for those living in high-deprivation neighbourhoods vs. those living in low-deprivation neighbourhoods was 1.23 (95% confidence interval, 1.16-1.30). High neighbourhood deprivation remained significantly associated with childhood asthma risk after adjustment for maternal socio-demographic characteristics (OR=1.08, p = 0.016).

CONCLUSIONS

This study is the largest so far on neighbourhood influences on childhood asthma. Our results suggest that neighbourhood characteristics affect the risk of hospitalization for childhood asthma independent of maternal socio-demographic characteristics.

Family history of venous thromboembolism (VTE) and risk of recurrent hospitalization for VTE: a nationwide family study in Sweden

BACKGROUND

Data concerning the importance of a family history of venous thromboembolism (VTE) for the risk of recurrent VTE are sparse. The aim of this nationwide study was to determine whether a family history of VTE is a risk factor for recurrent hospitalization for unprovoked VTE (deep vein thrombosis of the lower extremities or pulmonary embolism).

METHODS

We linked Multigeneration Register data on individuals aged 0-77 years to the Swedish nationwide Hospital Discharge Register data for the period 1987-2009 to compare the risk of hospitalization for unprovoked recurrent VTE among individuals with and without a parental or sibling history of VTE. We calculated hazard ratios (HRs) to determine the familial HR for recurrent hospitalization for VTE.

RESULTS AND CONCLUSIONS

The risk of recurrent VTE hospitalization was 1.20 (95% confidence interval [CI] 1.10-1.32) for individuals with affected parents, and 1.30 (95% CI 1.14-1.49) for those with affected siblings. The risk of recurrent VTE hospitalization in individuals with two affected parents was 1.92 (95% CI 1.44-2.58). There was an interaction between age at diagnosis of VTE and a family history of VTE, with a family history having a stronger effect on VTE risk in younger patients. We conclude that a family history of VTE is a modest risk factor for recurrent VTE hospitalization in Sweden.

Effects of pH, sodium chloride, and curing salt on the infectivity of Toxoplasma gondii tissue cysts

Toxoplasma gondii is one of the most common zoonotic parasites in the world. The parasite causes no or mild symptoms in immunocompetent humans. However, a high potential hazard exists for seronegative pregnant women and immunocompromised patients. The consumption of meat containing tissue cysts or oocyst-contaminated vegetables and fruits or the handling of cat feces poses a high risk of infection with T. gondii. It is known that raw minced meat, raw fresh sausages, and locally produced raw meat products are possible causes of T. gondii infection. The infectivity of T. gondii tissue cysts in meat products depends, among other factors, on the pH and the salt concentration. Therefore, the impact of these two factors on the tissue cysts was examined. For this purpose, dissected musculature and brain from experimentally infected mice (donor mice) were placed in a cell culture medium (RPMI 1640). The medium was adjusted to different pH values (pH 5, 6, and 7) with lactic acid and to different salt concentrations (2.0, 2.5, and 3.0%) with sodium chloride (NaCl) or nitrite-enriched curing salt (NCS) for the various tests. After storage at 4°C for different time periods, the materials were fed to bioassay mice. Later, the brains were examined for presence of T. gondii to assess the infectivity. The data show that T. gondii tissue cysts have a high pH tolerance. Cysts were infectious in the muscle for up to 26 days (pH 5). In contrast to their tolerance to pH, cysts were very sensitive to salt. Muscle cysts survived at an NaCl concentration of up to 2.0% only, and for no longer than 8 days. At NaCl concentrations of 2.5 and 3.0%, the cysts lost their infectivity after 1 day. When NCS instead of NaCl was used under the same conditions, T. gondii muscle cysts retained infectivity for only 4 days at 2.0%. Consequently, NCS (NaCl plus 0.5% nitrite) has a stronger effect on T. gondii cysts than does common table salt. Sausages produced with low NaCl concentration and short contact times pose a potential risk for susceptible individuals.

Venous thromboembolism does not share strong familial susceptibility with pre-eclampsia/eclampsia: a nationwide family study in Sweden

OBJECTIVE

Genetic variants associated with venous thromboembolism (VTE) have been suggested to be involved in the pathogenesis of pre-eclampsia/eclampsia (PEC/EC). This nationwide study aimed to determine whether VTE shares familial susceptibility with PEC/EC.

DESIGN

Population-based cohort study.

SETTING

Sweden.

SAMPLE

A total of 941 841 Swedish women delivering their first child between 1987 and 2008.

METHODS

Data from the Swedish Multigeneration Register were linked to the Swedish Hospital Discharge Register. The risk of PEC/EC was determined in primiparous women with a family history of VTE (in parents and/or siblings), compared with primiparous women without a family history of VTE. Odds ratios (ORs) were calculated by logistic regression.

MAIN OUTCOME MEASURE

PEC/EC in first pregnancy.

RESULTS

In total, 43 621 women had PEC/EC in association with their first pregnancy. The OR for PEC/EC in women with a family history of VTE was 1.06 (95% CI 1.01-1.11); however, a family history of VTE was associated with higher odds of PEC/EC among women with previous hypertension (OR 1.38, 95% CI 1.25-1.52).

CONCLUSION

A family history of VTE is weakly associated with PEC/EC risk, and is not clinically useful for the prediction of PEC/EC. The results of the present study suggest that it is unlikely that strong disease-causing mutations shared by VTE and PEC/EC are common in the Swedish population. The novel association between family history and PEC/EC among the subgroup with previous hypertension needs further confirmation in future studies.

Family history and risk of hospital treatment for varicose veins in Sweden

Background

Family history has been suggested as a risk factor for varicose veins, but recall bias may inflate the familial risks. The aim of this nationwide study was to determine familial risks for hospital treatment for varicose veins.

Methods

Data from the Swedish Multi-Generation Register of people aged 0-76 years were linked to Hospital Discharge Register data for 1964–2008. Standardized incidence ratios (SIRs) were calculated for individuals whose relatives were treated in hospital for varicose veins and compared with those whose relatives were not. Only main diagnoses of varicose veins were considered.

Results

A total of 39 396 people had hospital treatment for varicose veins. The familial SIR among offspring with one affected parent was 2·39 (95 per cent confidence interval 2·32 to 2·46). The SIR for those with one affected sibling was 2·86 (2·76 to 2·97). SIRs were increased in both men and women. The SIR for individuals with two or more affected siblings or with two affected parents was 5·88 (5·28 to 6·53) and 5·52 (4·77 to 6·36) respectively. The SIR for the wives of men treated for varicose veins was 1·69 (1·59 to 1·80); that for the husbands of women treated for varicose veins was 1·68 (1·58 to 1·79).

Conclusion

Using the Swedish Hospital Discharge Register, and thereby eliminating recall bias, family history of hospital treatment for varicose veins was associated with an increased risk of similar treatment among relatives. The increased spousal risk suggests a contribution from non-genetic factors.

Familial risks of unusual forms of venous thrombosis: a nationwide epidemiological study in Sweden

OBJECTIVE

This is the first nationwide study to determine familial risks of unusual forms of venous thrombosis amongst offspring of affected parents and amongst siblings.

DESIGN AND SETTINGS

The Swedish Multigeneration Register of 0- to 75-year-old subjects was linked to the Hospital Discharge Register for the period 1987-2007. Standardized incidence ratios (SIRs) were calculated for individuals whose relatives were hospitalized for venous thromboembolism (VTE), as determined by the International Classification of Diseases, compared to those whose relatives were not affected by VTE.

RESULTS

The total number of hospitalized patients with VTE was 45 362, of which 1824 (4.0%) were affected by a rare thrombotic condition. The familial SIRs in cases with a history of VTE in parents or siblings were significantly increased for migrating thrombophlebitis (1.81; 95% confidence interval (CI) 1.40-2.31), portal vein thrombosis (2.35; 95% CI 1.77-3.06), vena cava thrombosis (1.96; 95% CI 1.42-2.64) and cerebral venous thrombosis (1.74; 95% CI 1.30-2.28). Budd-Chiari syndrome (SIR, 0.92; 95% CI 0.24-2.38) and renal vein thrombosis (SIR, 1.72; 95% CI 0.62-3.77) were not significantly associated with parental or sibling history of VTE; however, these two conditions were very rare, and therefore, we cannot draw any definite conclusions from this finding.

CONCLUSIONS

Family history is an important risk factor for most unusual forms of VTE. Moreover, even the paraneoplastic phenomenon, migrating thrombophlebitis (Trousseau's syndrome), is associated with a family history of VTE. Thus, our data suggest that most rare forms of VTE have a familial background.

Parental history and venous thromboembolism: a nationwide study of age-specific and sex-specific familial risks in Sweden

BACKGROUND

The value of parental history as a risk indicator for venous thromboembolism (VTE) has not been determined in a nationwide setting.

OBJECTIVES

To perform the first nationwide study of age-specific and sex-specific familial VTE risks in offspring of parents hospitalized for VTE.

PATIENTS/METHODS

The Swedish Multigeneration Register of 0-75-year-old subjects was linked to the Hospital Discharge Register for 1987-2007. Standardized incidence ratios (SIRs) were calculated for individuals whose parents were hospitalized for VTE as compared with those whose parents were unaffected.

RESULTS

Among 45,362 hospitalized offspring cases with VTE, 4865 offspring of affected parents were identified with a familial SIR of 2.00 (95% confidence interval [CI] 1.94-2.05). Familial SIR was slightly higher for male offspring than for female offspring (2.08, 95% CI 2.00-2.16 vs. 1.91, 95% CI 1.84-1.99). The risk in offspring was further increased when both parents were affected (3.97, 95% CI 3.40-4.61), with high familial risks at ages 20-29 years (10.00, 95% CI 5.91-15.84). The familial risks for VTE among offspring were increased from the age of 10 years up to 75 years, with familial SIRs of 3.96 (95% CI 3.13-4.94) at age 10-19 years and 1.48 (95% CI 1.17-1.84) at ages 70-75 years. However, the absolute incidence rate increased with age.

CONCLUSIONS

Parental history is potentially useful for risk assessments of VTE, although age needs to be considered. Our results support the use of an age-dependent multicausal model to estimate the risk of VTE.

Efficacy and tolerability of diclofenac potassium sachets in migraine: a randomized, double-blind, cross-over study in comparison with diclofenac potassium tablets and placebo

A randomized, controlled, cross-over trial compared single doses of 50 mg diclofenac potassium sachets and tablets with placebo in 328 patients with migraine pain, treating 888 attacks. For the primary endpoint 24.7% of the patients were pain free at 2 h postdose with sachets, 18.5% for tablets and 11.7% for placebo. Treatment differences were significant for sachets vs. placebo (P<0.0001), tablets vs. placebo (P=0.0040) and for sachets vs. tablets (P=0.0035). The numbers needed to treat compared with placebo to achieve pain free at 2 h were 7.75 [95% confidence interval (CI) 5.46, 13.35] for sachets and 15.83 (95% CI 8.63, 96.20) for tablets. Sachets were also statistically superior to tablets for sustained headache response, sustained pain free and reduction in headache intensity within the first 2 h postdose measured on a visual analogue scale (P<0.05). Onset of analgesic effect was 15 min for sachets and 60 min for tablets. Fewer patients needed rescue medication, and there were marked improvements in accompanying symptoms and working ability with both sachets and tablets vs. placebo. No safety issues were identified. This study demonstrates that sachets offer patients suffering from migraine pain a more effective treatment with a faster onset of analgesia when compared with tablets.

Co-segregation of the PROS1 locus and protein S deficiency in families having no detectable mutations in PROS1

Inherited deficiency of protein S constitutes an important risk factor of venous thrombosis. Many reports have demonstrated that causative mutations in the protein S gene are found only in approximately 50% of the cases with protein S deficiency. It is uncertain whether the protein S gene is causative in all cases of protein S deficiency or if other genes are involved in cases where no mutation is identified. The aim of the current study was to determine whether haplotypes of the protein S gene cosegregate with the disease phenotype in cases where no mutations have been found. Eight protein S-deficient families comprising 115 individuals where previous DNA sequencing had failed to detect any causative mutations were analyzed using four microsatellite markers in the protein S gene region. Co-segregation between microsatellite haplotypes and protein S deficiency was found in seven of the investigated families, one family being uninformative. This suggests that the causative genetic defects are located in or close to the protein S gene in a majority of such cases where no mutations have been found.

Short-term treatment of primary fibromyalgia with the 5-HT3-receptor antagonist tropisetron. Results of a randomized, double-blind, placebo-controlled multicenter trial in 418 patients

We investigated the efficacy and tolerability of short-term treatment with tropisetron, a selective, competitive 5-HT3-receptor antagonist in fibromyalgia. The trial was designed as a prospective, multicenter, double-blind, parallel-group, dose-finding study. We randomly assigned 418 patients suffering from primary fibromyalgia to receive either placebo, 5 mg, 10 mg or 15 mg tropisetron once daily for 10 days. Clinical response was measured by changes in pain score, visual analog scale, tender point count and ancillary symptoms. Responders were prospectively defined as patients showing a 35% or higher reduction in pain score. Treatment with 5 mg tropisetron resulted in a significantly higher response rate (39.2%) than placebo (26.2%) (p < 0.05). In the visual analog scale, the group administered 5 mg tropisetron showed a significant improvement (p < 0.05) and the group administered 10 mg tropisetron showed a nonsignificant clinical benefit. The number of painful tender points was significantly reduced (p = 0.002) in the 5 mg tropisetron group. Regarding ancillary symptoms, the 5 mg tropisetron group showed a significant improvement (p < 0.05) in sleep and dizziness. The patients' overall assessment of efficacy was significantly higher for 5 mg (p = 0.016) and 10 mg (p = 0.002) tropisetron than for placebo. The safety and tolerability of tropisetron was good; gastrointestinal tract symptoms were the most frequently reported adverse events. Short-term treatment of fibromyalgia patients with 5 mg tropisetron for 10 days proved to be efficacious and well tolerated. In this study a bell-shaped dose-response curve was seen.

[Rational therapy of Alzheimer dementia based on current clinical studies]

Several preparations are currently available for the treatment of Alzheimer's dementia. To date only some of these drugs could show evidence of efficacy that would justify a recommendation for their therapeutic use. In the present survey, the results of five controlled clinical trials with acetylcholinesterase inhibitors versus Ginkgo-biloba extract have been analysed. The trials conducted with the acetylcholinesterase altogether have a larger patient population, an acceptable significance level of therapeutic effect as well as a lower rate of drop outs. Based on the documentation presented here, only the approved acetylcholinesterase inhibitors are currently to be recommended under strict scientific criteria for use in the treatment of Alzheimer's dementia.

Efficacy and tolerability of tropisetron in primary fibromyalgia--a highly selective and competitive 5-HT3 receptor antagonist. German Fibromyalgia Study Group

OBJECTIVE

Based on a potential role for serotonin receptors in fibromyalgia, we investigated the efficacy and tolerability of treatment with tropisetron, a highly selective, competitive inhibitor of the 5-HT3 receptor.

METHODS

In this prospective, multicenter, double-blind, parallel-group, dose-finding study, 418 patients suffering from primary fibromyalgia (ACR criteria) were randomly assigned to receive either placebo, 5 mg, 10 mg or 15 mg tropisetron once daily, respectively. The duration of treatment was 10 days. The clinical response was measured by changes in pain-score, visual analog scale (VAS), and the number of painful tender-points.

RESULTS

Treatment with 5 mg tropisetron resulted in a significantly higher response rate (39.2%) when compared with placebo (26.2%) (p=0.033). The absolute reduction in pain-score was -13.5% for 5 mg tropisetron, -13.0% for 10 mg tropisetron, and -6.3% for placebo (p<0.05). The effects of 15 mg tropisetron were similar to placebo, thus suggesting a bell-shaped dose-response curve. Compared with placebo, treatment with 5 mg tropisetron led to a significant improvement (p<0.05) in VAS, while a clear trend in terms of clinical benefit was seen with 10 mg tropisetron. The number of painful tender-points was also reduced significantly (p=0.002) in the 5 mg tropisetron group. Of interest, during the 12-month follow-up period, pain intensity of responders on 5 mg and 10 mg tropisetron was still markedly below baseline. The treatment was well tolerated, with gastro-intestinal complaints being the most frequently reported side effects, in keeping with the known safety profile for 5-HT3 receptor antagonists.

CONCLUSIONS

This study demonstrates the efficacy of short-term treatment with 5 mg tropisetron once daily in primary fibromyalgia. Treatment was well tolerated and prolonged clinical benefits were seen.

Sequence comparison of avian interferon regulatory factors and identification of the avian CEC-32 cell as a quail cell line

Interferon (IFN) regulatory factor-1 (IRF-1) is a well-characterized member of the IRF family. Previously, we have cloned cDNA of several members of the chicken IRF (ChIRF) family and studied the function of ChIRF-1 in the avian cell line CEC-32. The IRF-1 proteins from primary chicken embryo fibroblasts (CEF) and CEC-32 cells differed in their electrophoretic mobility. To characterize the different forms of IRF-1 in avian cells, we compared the sequences of IRF-1 cDNA from CEC-32 cells, primary CEF, and quail fibroblasts (QEF). The deduced amino acid sequences of IRF-1 cDNA from chicken and quail show high similarity. Comparison of genomic sequences of IRF-1 and IFN consensus sequence binding protein (ICSBP) also confirm the relatedness of the members of the IRF family in quail and chicken. Based on these data, it is concluded that the avian fibroblast cell line CEC-32 is derived from quail. This conclusion is further supported by deoxynucleotide sequence comparison of a DNA fragment in an avian MHC class II gene and by fluorescence in situ hybridization (FISH) using the vertebrate telomeric (TTAGGG) repeat. Chromosome morphology and the lack of interstitial hybridization signals in macrochromosomes suggest that the CEC-32 cell line has probably been derived from Japanese quail.

Factor V Q506 (resistance to activated protein C) and prognosis after acute coronary syndrome

Factor V:Q506 causing resistance to activated protein C (APC-resistance), is a risk factor for venous thrombosis. Some studies have indicated an association with arterial disease, especially in women. We investigated the prevalence of the FV:Q506 allele prospectively in 295 patients with acute coronary syndrome. Mortality and myocardial infarction rate were evaluated after 30 days and after 2 years. The FV:Q506 allele was found in 38 patients. In a Cox proportional hazards model, smokers carrying FV:Q506 had a higher risk of infarction or death within 30 days, compared to non-smokers with a normal genotype (relative risk 2.9 [95% CI 1.2-7.0]). The difference remained significant after 2 years (relative risk 2.8 [95% CI 1.2-6.5]). The effect of the FV:Q506 allele on clinical outcome in acute coronary syndrome has not previously been described. Our results demonstrate a gene-environment interaction between smoking and the FV:Q506 allele, with an increased risk of early complications after an acute ischemic event.

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.

The genomic structure of the chicken ICSBP gene and its transcriptional regulation by chicken interferon

The chicken interferon consensus sequence binding protein (ChICSBP) gene spans over 9 kb of DNA and consists, as its murine homolog, of nine exons. The first untranslated exon was identified by 5'-RACE technology. The second exon contains the translation initiation codon. Canonical consensus splice sites are found on every exon/intron junction. The introns are generally smaller than their mammalian counterparts. The ChICSBP and ChIRF-1 genes have been mapped by fluorescence in situ hybridization to different microchromosomes. The transcription start site has been mapped by primer extension. Inspection of the DNA sequence of a genomic clone containing the first exon and the region 1700-bp upstream revealed several potential cisregulatory elements of transcription. The ChICSBP mRNA is induced by recombinant ChIFN type I and ChIFN-gamma. A palindromic IFN regulatory element (pIRE) with high sequence homology to gamma activation site (GAS) sequences was functionally required in transient transfection assays for the induction of transcription by ChIFN-gamma.

A common 4G allele in the promoter of the plasminogen activator inhibitor-1 (PAI-1) gene as a risk factor for pulmonary embolism and arterial thrombosis in hereditary protein S deficiency

Reduced fibrinolytic capacity due to increased plasminogen activator inhibitor-1 (PAI-1) activity in plasma is a common finding in patients with coronary heart disease or venous thromboembolism, although its clinical significance is debated. Recently, a dimorphism in the PAI-1 promoter (4G-5G) has been reported and homozygosity for the 4G allele is associated with increased transcription and higher PAI-1 levels. Homozygous 4G genotype has been suggested to be a risk factor for myocardial infarction. In the present study, the 4G-5G dimorphism was determined in 349 individuals from 21 thrombophilic families with hereditary protein S deficiency and in 140 unrelated healthy controls. Among the 143 protein S deficient individuals, there was no relationship between deep or superficial venous thrombosis and the PAI-1 dimorphism. However, 26% (12/46) of individuals having protein S deficiency combined with homozygosity for the 4G allele had suffered pulmonary embolism as compared to 7% (7/97) of protein S deficient individuals carrying at least one 5G allele (p = 0.0019). In protein S deficient individuals, arterial thrombosis was found to be associated with smoking and 4G homozygosity. No association was found between the PAI-1 dimorphism and arterial or venous thromboembolism in family members without protein S deficiency. In conclusion, the PAI-1 genotype affects the phenotypic expression of thrombophilia in protein S deficient individuals.

A new direct, fast and quantitative enzyme-linked ligandsorbent assay for measurement of free protein S antigen

A new method to determine the concentration of free protein S in plasma is described. It is an enzyme-linked ligandsorbent assay (ELSA) which utilises the protein S binding capacity of the natural ligand C4b-binding protein (C4BP) to capture the free protein S from plasma samples. The use of C4BP as ligand in the assay is possible due to the high affinity (Kd = 0.1 nM) of the interaction between protein S and C4BP and to a slow rate of complex dissociation. A monoclonal antibody (HPS 54) was conjugated with horseradish peroxidase and used as target antibody. This antibody recognises a Ca2+ dependent epitope in the first EGF-like domain of protein S and does not interfere with C4BP binding sites of protein S. Addition of calcium in the assay helped prevent dissociation of the C4BP-protein S-HPS 54 complex. Three different experiments demonstrated the assay to be specific for free protein S. First, near-identical dose response curves were obtained with protein S in plasma and with purified protein S. Second, addition of purified C4BP to normal plasma resulted in loss of free protein S. Third, protein S depleted plasma gave zero values and around 80% of purified protein S added to protein S depleted plasma, and approximately 70% of protein S added to protein S deficient plasma samples, was recovered with the assay. The assay is fast (involves only a single incubation step of 30 min), sensitive and the range of measurement is 3% to 200% of free protein S when plasma dilution 1:20 represents 100%. Intra- and inter-assay coefficients of variation at two levels were 2.3-4.3% and 5.1-7.4%, respectively. In a large protein S deficient family, the assay showed 100% sensitivity and specificity for the causative mutation. Moreover, free protein S levels in anticoagulated protein S deficient patients were completely separated from those obtained in non-anticoagulated controls. The new assay for free protein S is suitable for automation and it provides a useful means for routine clinical purposes to detect protein S deficiencies.

Clarification of the risk for venous thrombosis associated with hereditary protein S deficiency by investigation of a large kindred with a characterized gene defect

BACKGROUND

Protein S is an important regulatory protein of the coagulation cascade. The risk for venous thrombosis associated with protein S deficiency has been uncertain because all previous risk estimates used phenotypic evaluation alone, which can be ambiguous.

OBJECTIVE

To quantitate the risk for thrombosis associated with a characterized protein S gene mutation that causes a Gly295-->Val substitution and protein S deficiency.

DESIGN

Retrospective study of a single extended family.

SETTING

University hospital referral center.

PARTICIPANTS

A 122-member protein S-deficient family, in which 44 members had a recently characterized gene defect.

MEASUREMENTS

Comprehensive history of thrombosis, history of exposure to acquired risk factors for thrombosis, levels of total and free protein S antigen, and genotype for the mutation causing the Gly295-->Val substitution.

RESULTS

Kaplan-Meier analysis of thrombosis-free survival showed that the probability of remaining free of thrombosis at 30 years of age is 0.5 (95% CI, 0.33 to 0.66) for carriers of the Gly295-->Val mutation compared with 0.97 (CI, 0.93 to 1.0) for normal family members (P < 0.001). In a multivariate Cox regression model that included smoking and obesity, the mutation was a strong independent risk factor for thrombosis (hazard ratio, 11.5 [CI, 4.33 to 30.6]; P < 0.001). For free (but not total) protein S antigen levels, the distributions of persons with and persons without the mutation did not overlap.

CONCLUSIONS

Protein S deficiency, as defined by the presence of a causative gene mutation or a reduced level of free protein S antigen, is a strong independent risk factor for venous thrombosis in a clinical affected family.

Resistance to activated protein C, the FV: Q506 allele, and venous thrombosis

Vitamin K-dependent protein C is an important regulator of blood coagulation. After its activation on the endothelial cell surface by thrombin bound to thrombomodulin, it cleaves and inactivates procoagulant cofactors Va and Villa, protein S and intact factor V working as cofactors. Until recently, genetic defects of protein C or protein S were, together with antithrombin III deficiency, the established major causes of familial venous thromboembolism, but they were found in fewer than 5-10% of patients with thrombosis. In 1993, inherited resistance to activated protein C (APC) was described as a major risk factor for venous thrombosis. It is found in up to 60% of patients with venous thrombosis. In more than 90% of cases, the molecular background for the APC resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine (R) at position 506 by a glutamine (Q). Mutated factor V (FV: Q506) is activated by thrombin or factor Xa in normal way, but impaired inactivation of mutated factor Va by APC results in life-long hypercoagulability. The prevalence of the FV:Q506 allele in the general population of Western countries varies between 2 and 15%, whereas it is not found in several other populations with different ethnic backgrounds. Owing to the high prevalence of FV:Q506 in Western populations, it occasionally occurs in patients with deficiency of protein S, protein C, or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting severe thrombophilia to be a multigenetic disease.

A novel thrombomodulin gene mutation in a patient suffering from sagittal sinus thrombosis

Thrombomodulin is an endothelial cell membrane glycoprotein that promotes protein C activation. It has been clearly demonstrated that the anticoagulant functions of the protein C system are important in the prevention of thromboembolic disease. Patients with protein C or protein S deficiency and/or resistance to activated protein C (APC resistance) are at higher risk for developing thromboembolic disease. The first mutation in the thrombomodulin gene was discovered in an American patient suffering from pulmonary embolism at the age of 45 (Ohlin and Marlar 1995). Here we report a case of sagittal sinus thrombosis in a 42-year-old Swedish woman. She was found to carry a heterozygous point mutation changing G127 to A, predicting an Ala25 to a Thr change in the mature thrombomodulin protein. This mutation was also found in her 16-year-old daughter, who so far has not suffered from any thrombotic events. The patient had no other detectable prothrombotic genetic defects associated with the coagulation system. This case supports the hypothesis of an association between mutations in the thrombomodulin gene and venous thrombosis.

The 20210 A allele of the prothrombin gene is a common risk factor among Swedish outpatients with verified deep venous thrombosis

A dimorphism in the 3'-untranslated region of the prothrombin gene (G to A transition at position 20210) has recently been reported to be associated with increases in plasma prothrombin levels and in the risk of venous thrombosis. We have examined the prothrombin dimorphism among 99 unselected outpatients with phlebography verified deep venous thrombosis, and in 282 healthy controls. The prevalence of the 20210 A allele was 7.1% (7/99) in the patient group, and 1.8% (5/282) in the healthy control group (p = 0.0095). The relative risk of venous thrombosis was calculated to be 4.2 (95% CI, 1.3 to 13.6), and was still significant when adjustment was made for age, sex and the factor V:R506Q mutation causing APC resistance [odds ratio 3.8 (95% CI, 1.1 to 13.2)]. As previously reported, 28% of the patients were carriers of the factor V:R506Q mutation. Thus, 34% (one patient carried both traits) of unselected patients with deep venous thrombosis were carriers of an inherited prothrombotic disorder. To sum up, our results confirm the 20210 A allele of the prothrombin gene to be an important risk factor for venous thrombosis.

Genetic and phenotypic analysis of a large (122-member) protein S-deficient kindred provides an explanation for the familial coexistence of type I and type III plasma phenotypes

Protein S deficiency is a known risk factor for thrombosis. The coexistence of phenotypic type I (reduction in total and free antigen) and type III (reduction in free antigen only) protein S deficiencies in 14 of 18 families was recently reported. We investigated the cause of this phenotypic variation in the largest of these families (122 family members, including 44 affected individuals) using both molecular genetic and phenotypic analysis. We have identified a sole causative mutation (Gly295Val) in three family members representative of the variable phenotype. Complete cosegregation of the mutation with reduced free protein S antigen levels was found, regardless of the total antigen level. Analysis of phenotypic data showed high correlations between total protein S antigen and age in both normal and protein S-deficient family members, irrespective of gender. Free protein S antigen levels were not influenced by age, a finding explained by an association between beta-chain containing C4b-binding protein (C4bBP-beta+) antigen levels and age. We propose that the identified Gly295Val mutation causes quantitative, or type I, protein S deficiency, and that as age increases the total protein S antigen level normalizes with respect to the reference plasma pool, giving rise to a type III protein S-deficient phenotype.

The factor VR506Q mutation causing APC resistance is highly prevalent amongst unselected outpatients with clinically suspected deep venous thrombosis

OBJECTIVE

Resistance to activated protein C (APC resistance), caused by a single point mutation in the factor V gene (FV:R506Q), is a major risk factor for venous thrombosis. As the significance of this mutation among unselected outpatients with deep-vein thrombosis (DVT) is not established, we have studied its prevalence among consecutive outpatients attending the emergency room due to a clinically suspected DVT.

DESIGN, SETTING AND SUBJECTS

The FV:R506Q mutation was determined in 223 consecutive Swedish outpatients with clinically suspected DVT, and in 288 healthy controls. Using phlebography, the patients were classified as DVT-positive or DVT-negative.

MAIN OUTCOME MEASURE

The prevalence of FV:R506Q mutation.

RESULTS

The prevalence of the FV:R506Q mutation was 28% (28/99) in the DVT-positive subgroup (relative risk: 3.1; 95% CI: 1.7-5.5), and 23% (28/124) in the DVT negative subgroup (relative risk: 2.0; 95% CI: 1.1-3.6), as compared to 11% (32/288) in the control group. In the DVT-positive subgroup, the FV:R506Q mutation was most common among younger patients with primary thrombosis (47%) and least common among older patients with secondary thrombosis (19%). The high prevalence of FV:R506Q mutation among DVT-negative patients was associated with a high frequency of previous venous thrombosis. Thus, 46% (13/28) of the DVT-negative FV:R506Q carriers had a history of thrombosis, compared with only 22% (21/96) of the DVT-negative patients lacking the mutation (P = 0.01).

CONCLUSION

To sum up, the FV:R506Q mutation is present in more than a quarter of Swedish DVT-positive outpatients with clinically suspected DVT, indicating that APC-resistance is a major thrombotic risk factor contributing to the high incidence of venous thrombosis in Sweden.

Cloning of chicken interferon regulatory factor-2 (IRF-2) cDNA: expression and mapping of the IRF-2 gene

A cDNA clone encoding a member of the avian interferon regulatory factor (IRF) family homologous to mammalian IRF-2 was isolated from cDNA library from poly[rI:rC]-induced chicken embryo fibroblasts (CEF). The deduced amino acid sequence shows a characteristic DNA binding domain of 124 amino acids at the amino-terminal end with 96.8% identity to human and 96% to mouse IRF-2. Identities in the C-terminal part are 77.5% and 77%, respectively. Identity to all other known members of the chicken IRF (Ch-IRF) family is distinctly lower. In C32 cells, an IRF-2 mRNA of 2.4 kb is constitutively expressed in very low amounts but is inducible by Ch-IFN in the absence or presence of cycloheximide. The Ch-IRF-2 gene is a single copy gene and was mapped by fluorescence in situ hybridization to the long arm of chromosome 4.

Evaluation of original and modified APC-resistance tests in unselected outpatients with clinically suspected thrombosis and in healthy controls

APC-resistance is the most common hereditary condition associated with venous thrombosis. It is in a majority of cases due to a single point mutation in the factor V gene (FVR506Q). Currently used functional APC-resistance tests have 85-90% sensitivity and specificity for the FVR506Q mutation. A modified test which includes predilution of patient plasma in factor V depleted plasma has increased the sensitivity and specificity for the factor V mutation. However, neither the original nor the modified APC-resistance test have been evaluated in patients with acute thrombotic events. We have therefore used the original and the modified APC-resistance tests in 220 patients with clinically suspected acute deep venous thrombosis and in 278 healthy controls. The FVR506Q mutation was determined in all patients. The patients were classified as either DVT (deep venous thrombosis)-negative or DVT-positive depending on the outcome of contrast phlebography. In individuals with normal factor V genotype, the original APC-resistance test gave significantly lower APC-ratio values both in DVT-positive and DVT-negative patients than in healthy controls. The specificity of the original APC-resistance test for the FVR506Q mutation in controls and in DVT-negative and DVT-positive patients were 85%, 54% and 28%, respectively, when a cut off APC-ratio of 3.2 which insured 100% sensitivity was used. Using the modified APC-resistance test, essentially no difference in APC-ratios between patients with normal factor V genotype and healthy controls with normal factor V genotype was observed. The modified APC-resistance test had a specificity for the FVR506Q mutation of 98.8% at an APC-ratio cut off of 2.1 which ensured 100% sensitivity. The original APC-resistance test gave lower APC-ratios in women than in men and in patients with acute thrombosis as compared to controls. In conclusion, the modified APC-resistance test is highly sensitive and specific for the FVR506Q mutation. This test can be used in clinical practice as an easy to perform screening test for the FVR506Q allele. Moreover, the test performs equally well in patients with acute suspected venous thrombosis as in healthy controls.

A common thrombomodulin amino acid dimorphism is associated with myocardial infarction

Endothelial dysfunction and haemostatic imbalance are believed to be important aetiological factors in the development of acute coronary syndromes. Thrombomodulin (TM) is an integral membrane protein crucial for normal endothelial function and activation of the protein C anticoagulant pathway. We have investigated the importance of a common C/T dimorphism in the TM gene (nucleotide 1418) for development of premature myocardial infarction (MI). The C/T dimorphism predicts an Ala455 to Val replacement in the sixth EGF-like domain of TM. The dimorphism was investigated in 97 MI survivors and 159 healthy controls. The C allele was significantly more frequent among patients than controls (p = 0.035). The allele frequency for the C allele was 0.82 in the patients and 0.72 in the control group. The plasma concentration of TM was investigated among healthy controls but was not related to the C/T dimorphism. In conclusion, the association of the C allele with premature MI, suggests that the TM gene and the C/T dimorphism may be aetiological factors involved in the pathogenesis of MI. Possibly, the Ala455 to Val replacement may affect the function of the TM molecule and the activation of the protein C anticoagulant pathway.

Activated protein C resistance caused by a common factor V mutation has a single origin

A point mutation (FV:R506Q) in the human coagulation factor V gene is associated with resistance to activated protein C and life-long increased risk of venous thrombosis. The mutation is common in populations of Caucasian origin but virtually absent among other populations. In this study of 140 healthy Swedish volunteers and 110 homozygotes for the FV:R506Q mutation, we determined the allele frequencies of the FV:R506Q mutation and four other dimorphisms, C/T at nucleotide positions 2298 and 2325, and A/G at nucleotide positions 2379 and 2391. Manifest linkage disequilibrium was found between the FV:R506Q mutation and the four different dimorphisms. The finding of a single FV:R506Q haplotype in all homozygotes constitutes strong evidence of a common ancestor of Swedish individuals with the FV:R506Q mutation.

Activated protein C resistance due to a common factor V gene mutation is a major risk factor for venous thrombosis

Inherited resistance to activated protein C (APC) was recently discovered to be a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. It is caused by a single point mutation in the gene for factor V, which predicts substitution or arginine (R) at position 506 with a glutamine (Q). Accordingly, the activated form of mutated factor V (FVa:Q506) is more slowly degraded by activated protein C than normal FVa (FVa:R506) is, resulting in hypercoagulability and a lifelong 5- to 10-fold increased risk of venous thrombosis. Previously known inherited hypercoagulable states, i.e. deficiencies of the anticoagulant proteins antithrombin III, protein S, and protein C, are found fewer than 10-15% of thrombosis patients in western countries, whereas inherited APC resistance is present in 20-60% of such patients. The FV mutation is common in populations of Caucasian origin, with prevalences ranging from 1-15%, whereas it is not found in certain other ethnic groups such as Japanese and Chinese. The high prevalence of APC resistance, in combination with the availability of simple laboratory tests, will have a profound influence on the development of therapeutic and prophylactic regimens for thrombosis and will, it is hoped, result in a decreased incidence of thromboembolic events.

Factor V:Q506 mutation and anticardiolipin antibodies in systemic lupus erythematosus

Inherited resistance to activated protein C (APC resistance) is an important risk factor of venous thrombosis. It is caused by a point mutation in the gene coding for coagulation factor V, called FV:Q506. Arterio-venous thrombosis is a common and serious medical problem in patients with systemic lupus erythematosus (SLE). We studied the prevalence of the factor V mutation associated with APC resistance and IgG anticardiolipin antibodies (aCLs) in an epidemiological cohort of 78 Swedish SLE patients, to determine their roles as risk factors for thrombosis. In addition, a detailed evaluation of the clinical manifestations in these patients was performed. Totally, 19 (24%) of the 78 SLE patients had thrombosis, 11 (14%) had venous thrombosis and 8 (10%) had a cerebral infarction caused by occlusion of cerebral vessels. Twenty-six (33%) SLE patients were aCL positive and 8 (10%) were heterozygous for the factor V mutation. Only one of the patients with venous thrombosis and one of the patients with cerebral thrombosis had the FV:Q506 mutation, whereas 3 patients with venous thrombosis and 5 patients with cerebral infarction were aCL positive. Eleven of 19 patients with heart valve disease were aCL positive, a statistically significant association (P = 0.01). In conclusion, we found no statistically significant association between venous thrombosis and FV:Q506 mutation or venous thrombosis and aCL positivity. There was, however, an association between heart valve disease and aCL positivity.

Inherited resistance to activated protein C caused by presence of the FV:Q506 allele as a basis of venous thrombosis

Inherited resistance to activated protein C (APC) was recently discovered as a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. In a majority of cases, APC resistance is associated with a single point mutation in the factor V gene, which results in substitution of arginine (R) at position 506 by glutamine (Q) (FV:Q506). The mutation renders factor Va partially resistant to degradation by activated protein C (APC), which leads to a hypercoagulable state and a life-long 5-10-fold increased risk of venous thrombosis. The previously known inherited deficiencies of antithrombin, protein S or protein C, are in western societies together found in less than 10-15% of thrombosis patients, whereas APC resistance is present in 20 to 60% of the patients. A functional APC resistance test, which includes predilution of the patient plasma with factor V deficient plasma, is 100% sensitive and specific for the presence of FV:Q506. The FV:Q506 allele is common in populations of Caucasian origin (prevalence ranging between 1 and 15%), whereas it is not found in certain other ethnic groups such as in Japanese and Chinese. The thrombotic risk in individuals with APC resistant may be further increased by other genetic defects such as protein C or protein S deficiency and by exposure to circumstantial risk factors such as oral contraceptives, pregnancy, immobilisation and surgery.

Rapid plasma virus and CD4+ T-cell turnover in HIV-1 infection: evidence for an only transient interruption by treatment

OBJECTIVES

To analyse the short-term kinetics of viral plasma RNA and CD4+ T cells numbers in patients with different initial CD4+ T-cell counts treated with different antiretroviral regimens.

METHODS

In 10 HIV-1 positive patients, in vivo kinetics of plasma HIV RNA and CD4+ T cells were studied during antiretroviral treatment. Lymphocyte subpopulation analysis, quantitative polymerase chain reaction (PCR), p24 antigen enzyme immunoassay (EIA) and beta 2-microglobulin EIA were performed at days 0, 3, 7, 10, 14, 21 and 28 of treatment. One additional patient served as a control. The resulting curves were fitted. Half-lives were calculated using the time constant T of decrease or increase [T1/2 = In(2) x T]. Calculations of virus and CD4+ T-cell turnover were multiplied by the total blood volume.

RESULTS

Viral plasma RNA half-life ranged from 1.1 to 5.1 days, independent of prior or actual treatment and initial CD4+ T-cell count. The calculated peripheral blood viral plasma RNA turnover varied between 0.02 and 55.8 x 10(8) copies/ml/day and showed some negative correlation with initial CD4+ T-cell counts. CD4+ T-cell turnover estimates ranged from 0.01 to 7.5 x 10(8) cells/day. Most patients showed an immediate reincrease of virus load after the nadir. Changes in HIV p24 antigen paralleled HIV plasma RNA in p24 antigen-positive patients. beta 2-microglobulin decreased until day 7-15 in all but one case and rapidly reincreased to pretreatment values.

CONCLUSIONS

The kinetics of virus and CD4+ T-cell turnover are uniformly rapid throughout a wide range of initial CD4+ T-cell counts. The magnitude of virus turnover varies considerably among individuals and appears to be inversely related to the initial CD4+ T-cell count. These data also argue for a rapid resumption of virus production and lymphocyte turnover during treatment.

Methylamine accumulation in cultured cells as a measure of the aqueous storage compartment in the laboratory diagnosis of genetic lysosomal diseases

Intracellular accumulation of the lysosomotropic compound [14C]methylamine was used to estimate the size of the lysosomal compartment in fibroblasts cultured from patients with a variety of lysosomal storage diseases. In previous work from our laboratory, it was shown that methylamine accumulation was significantly increased in diseases with infantile or juvenile onset and storage of predominantly water-soluble material such as in the mucopolysaccharidoses, mucolipidoses, and oligosaccharidoses. In the present study, methylamine incorporation was abnormally increased in cells from patients with glycogenosis type II and with Niemann-Pick type C disease, whereas it was normal in other sphingolipidoses and in the late-infantile and juvenile forms of neuronal ceroid lipofuscinoses. The methylamine test was also checked regarding its potential use for prenatal diagnostic testing. In model systems with cultured amniotic or chorionic villus cells, lysosomal storage was experimentally induced by the cathepsin inhibitor leupeptin and was readily detected when compared to untreated controls. Cultured amniotic cells from a fetus with mucopolysaccharidosis II were found to incorporate significantly higher amounts of [14C]methylamine than the normal controls. The results indicate that the methylamine accumulation method is an additional tool in the diagnosis and prenatal diagnosis of lysosomal diseases with abnormal storage of water-soluble material.

Resistance to activated protein C, the FV:Q506 allele, and venous thrombosis

Vitamin K-dependent protein C is an important regulator of blood coagulation. After its activation on the endothelial cell surface by thrombin bound to thrombomodulin, it cleaves and inactivates procoagulant cofactors Va and VIIIa, protein S and intact factor V working as cofactors. Until recently, genetic defects of protein C or protein S were, together with antithrombin III deficiency, the established major causes of familial venous thromboembolism, but they were found in fewer than 5-10% of patients with thrombosis. In 1993, inherited resistance to activated protein C (APC) was described as a major risk factor for venous thrombosis. It is found in up to 60% of patients with venous thrombosis. In more than 90% of cases, the molecular background for the APC resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine (R) at position 506 by a glutamine (Q). Mutated factor V (FV:Q506) is activated by thrombin or factor Xa in normal way, but impaired inactivation of mutated factor Va by APC results in life-long hypercoagulability. The prevalence of the FV:Q506 allele in the general population of Western countries varies between 2 and 15%, whereas it is not found in several other populations with different ethnic backgrounds. Owing to the high prevalence of FV:Q506 in Western populations, it occasionally occurs in patients with deficiency of protein S, protein C, or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting severe thrombophilia to be a multigenetic disease.

Prevalence of factor V gene mutation amongst myocardial infarction patients and healthy controls is higher in Sweden than in other countries

OBJECTIVE

Haemostatic imbalance may be an aetiological factor in the development of acute coronary syndromes. Inherited resistance to activated protein C (APC) is a common disorder associated with hypercoagulability and lifelong risk of venous thrombosis. APC resistance is due to a single mutation in the gene coding for coagulation factor V (FV:Q506). To test the importance of the FV:Q506 mutation in premature myocardial infarction (MI), its prevalence was investigated in Swedish patients with MI before the age of 50 years.

DESIGN, SETTING AND SUBJECTS

In a retrospective case-control study, the FV:Q506 mutation was investigated in 101 survivors of MI (79 men, 22 women) and in 101 healthy sex- and age-matched controls.

MAIN OUTCOME MEASURE

The prevalence of FV:Q506 mutation.

RESULTS

The FV:Q506 mutation was found in 18% of patients versus 11% of controls (P = 0.16). The mutation was significantly more frequent amongst male patients than amongst controls (23 vs. 10%; P = 0.03), the calculated odds ratio being 2.6 (95% CI, 1.1-6.4).

CONCLUSION

The high prevalence of the FV:Q506 mutation found amongst Swedish MI patients, especially amongst men, is noteworthy, and calls for further studies on the outcome of MI in APC-resistant patients. The prevalence of the FV:Q506 mutation in controls is higher than figures reported from other countries, suggesting that at least 10% of the Swedish population are carriers of a congenital prothrombotic disorder.

Elevated levels of prothrombin activation fragment 1 + 2 in plasma from patients with heterozygous Arg506 to Gln mutation in the factor V gene (APC-resistance) and/or inherited protein S deficiency

Inherited resistance to activated protein C (APC-resistance), caused by a point mutation in the factor V gene leading to replacement of Arg(R)506 with a Gln (Q), and inherited protein S deficiency are associated with functional impairment of the protein C anticoagulant system, yielding lifelong hypercoagulability and increased risk of thrombosis. APC-resistance is often an additional genetic risk factor in thrombosis-prone protein S deficient families. The plasma concentration of prothrombin fragment 1 + 2 (F1 + 2), which is a marker of hypercoagulable states, was measured in 205 members of 34 thrombosis-prone families harbouring the Arg506 to Gln mutation (APC-resistance) and/or inherited protein S deficiency. The plasma concentration of F1 + 2 was significantly higher both in 38 individuals carrying the FV:Q506 mutation in heterozygous state (1.7 +/- 0.7 nM; mean +/- SD) and in 48 protein S deficient cases (1.9 +/- 0.9 nm), than in 100 unaffected relatives (1.3 +/- 0.5 nM). Warfarin therapy decreased the F1 + 2 levels, even in those four patients who had combined defects (0.5 +/- 0.3 nM). Our results agree with the hypothesis that individuals with APC-resistance or protein S deficiency have an imbalance between pro- and anti-coagulant forces leading to increased thrombin generation and a hypercoagulable state.

Familial thrombophilia: clinical and molecular analysis of Swedish families with inherited resistance to activated protein C or protein S deficiency

This report describes the characterization of Swedish families with inherited resistance to activated protein C (APC resistance) and/or protein S deficiency, two genetic disorders associated with functional impairment of the protein C anticoagulant pathway. The APC resistance phenotype was linked to the factor V gene locus in a kindred with independent inheritance of APC resistance and protein S deficiency. A point mutation changing Arg506 to a Gln (FV:Q506) in the factor V gene was the cause of APC resistance. In studies of 50 families with hereditary APC resistance, the FV:Q506 mutation was identified in 94% (47/50) of the families, and the thrombotic risk was found to be dependent on the factor V genotype. Moreover, 18 families with hereditary deficiency of free protein S were investigated. Type I protein S deficiency (low free and total protein S) and type III deficiency (low free but normal total protein S) coexisted in 78% (14/18) of the families, suggesting the two types to be phenotypic variants of the same genetic disorder. Deficiency of free protein S was caused by equimolar relationship between protein S and beta-chain containing isoforms of C4BP. Though protein S deficiency was a strong risk factor for thrombosis, the FV:Q506 mutation was identified as an additional genetic risk factor in 39% of the families. Thus, familial thrombophilia is a multiple gene disorder. The thrombophilic tendency associated with APC resistance or protein S deficiency was related to increased levels of prothrombin fragment 1 + 2, reflecting increased activation of the common coagulation pathway.

Activated protein C resistance: from phenotype to genotype and clinical practice

The anticoagulant protein C system is an important regulator of the blood coagulation process. Its targets are the procoagulant cofactors factor Va and factor VIIIa, which are cleaved and inactivated by activated protein C, protein S and intact factor V working as cofactors. Genetic defects of protein C or protein S were, together with antithrombin III deficiency, the previously established major causes of familial venous thromboembolism. However, these abnormalities are found in less than 5-10% of patients with thrombosis. Inherited resistance to activated protein C was recently identified as a major risk factor for venous thromboembolism. The activated protein C-resistance phenotype is found in 20-60% of the patients with venous thrombosis, depending on selection criteria and on the prevalence of activated protein C-resistance in the population. The frequency of activated protein C-resistance is 2-10% in the normal populations studied so far. In more than 90% of cases, the molecular background for the activated protein C-resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine at position 506 by a glutamine. Mutated factor V is activated by thrombin or factor Xa in the normal way, but impaired inactivation of mutated factor Va by activated protein C results in a life-long hypercoagulability. Owing to the high prevalence of activated protein C-resistance in the population, it occasionally occurs in patients with deficiency of protein S, protein C or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting thrombophilia to be a multigenetic disease.

Resistance to activated protein C caused by a factor V gene mutation

Each year, approximately one in 1000 individuals suffers from venous thromboembolism. The pathogenesis of the disease is multifactorial and a thrombotic event is the result of a combination of genetic and circumstantial risk factors. Until recently, genetic defects could only be identified in a minority of thrombosis patients. The discovery of inherited resistance to activated protein C as a risk factor for thrombosis changed the situation for the better. In Western countries, activated protein C resistance is found in 20% to 60% of patients with thrombosis. Activated protein C resistance is caused by a single point mutation in the Factor V gene, leading to replacement of Arg(R)506 in the activated protein C cleavage site of Factor V with a Gln(Q). As a result, the activated protein C-mediated cleavage and inhibition of mutated Factor V (FV:Q506) is impaired, which leads to increased thrombin generation, a hypercoagulable state, and a life-long increased risk of thrombosis.

Resistance to activated protein C as an additional genetic risk factor in hereditary deficiency of protein S

Inherited resistance to activated protein C (APC), which is caused by a single point mutation in the gene for factor V, is a common risk factor for thrombosis. In this study, the prevalence of APC resistance in 18 unrelated thrombosis-prone families with inherited protein S deficiency was investigated to determine its role as additional genetic risk factor for thrombosis. In addition, a detailed evaluation of the clinical manifestations in these families was performed. Venous thrombotic events had occurred in 47% of the protein S-deficient patients (64/136) and in 7% of relatives without protein S deficiency (14/191). As estimated from Kaplan-Meier analysis, 50% of protein S-deficient family members and 12% of those without protein S deficiency had had manifestation of venous thromboembolism at the age of 45 years. The age at the first thrombotic event ranged from 10 to 81 years (mean, 32.5 years) and a large intrafamilial and interfamilial variability in expression of thrombotic symptoms was seen. The factor V gene mutation related to APC resistance was present in 6 (38%) of 16 probands available for testing; in total, the mutation was found in 7 (39%) of the 18 families. In family members with combined defects, 72% (13/18) had had thrombosis as compared with 19% (4/21) of those with only protein S deficiency and 19% (4/21) of those with only the factor V mutation. In conclusion, APC resistance was found to be highly prevalent in thrombosis-prone families with protein S deficiency and was an additional genetic risk factor for thrombosis in these families. The results suggest thrombosis-prone families with protein S deficiency often to be affected by yet another genetic defect.