Hyperhomocysteinaemia, coagulation pathway activation and thrombophilia in patients with inflammatory bowel disease

BACKGROUND: The 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism encoding the thermolabile variant is, when present as homozygote type (TT variant), a known genetic cause of mild hyperhomocysteinaemia (HHCY). This polymorphism has been observed in increased numbers in patients with inflammatory bowel disease (IBD). Coagulation and fibrinolysis are activated in patients with active IBD, but it is not known whether raised plasma homocysteine (HCY) found in patients with IBD significantly contributes to this activation. The aim of this study was to investigate if HHCY or presence of the TT variant significantly induces a hypercoagulable state in IBD patients receiving anti-inflammatory therapy during active disease, and to study if genetic determinants for thromboembolic disease are more frequent in these patients. METHODS: The study was designed as a cross-sectional study in an outpatient clinic comprising 106 IBD patients receiving anti-inflammatory therapy. Markers of coagulation were measured in order to elucidate whether patients with HHCY or the MTHFR TT variant were hypercoagulant compared with patients with no impairment of HCY metabolism. In addition, markers of inflammation and acute-phase reactants were measured in order to compare activity during active disease and during remission. Genetic determinants of thromboembolic disease in patients with IBD and in relevant controls were investigated in the expectation of a more frequent occurrence of these markers of thrombophilia if hypercoagulability could be a primary or contributory factor in IBD. RESULTS: No significant difference could be found in coagulation activity, acute-phase reactants or inflammatory markers in IBD patients with the TT variant of the 677C-->4T polymorphism or high (>15 micromol/L) plasma HCY levels, compared with IBD patients with no impairment of HCY metabolism. In patients with IBD, the coagulation activity was significantly increased during active disease compared with a state of remission. As expected, a significant difference regarding interleukin 6, C-reactive protein and erythrocyte sedimentation rate was present in IBD, comparing active disease with a state of remission. No significant complement activation was present in either of the groups or during active disease. Neither of the allele frequencies of genetic determinants for thrombophilia (coagulation factor V 1691G-->A (factor V Leiden) and factor II 20210G-->A polymorphisms) in the background population differed significantly from that in IBD patients. CONCLUSIONS: This study found no correlation between the MTHFR TT variant or HHCY and a hypercoagulable state in IBD patients receiving anti-inflammatory treatment. This coagulation activity is high during exacerbations of disease, but a considerable reduction is seen in patients on anti-inflammatory therapy compared with non-treated patients. Coagulation activation in IBD is probably a consequence of the inflammatory nature of the disease. That thrombophilia could be a contributory or primary factor in the development of IBD is not supported by the present study, as the frequencies for the genetic determinants for thrombophilia are similar in IBD patients and controls.     

Increased prevalence of methylenetetrahydrofolate reductase C677T variant in patients with inflammatory bowel disease, and its clinical implications

BACKGROUND: Inflammatory bowel disease (IBD) is associated with an increased incidence of thromboembolic disease. Hyperhomocysteinaemia (hyper-tHcy), a condition associated with the C677T variant of 5, 10-methylenetetrahydrofolate reductase (MTHFR), is linked with an increased incidence of thromboembolic disease. Hyper-tHcy has been reported in patients with IBD. AIMS: To assess the prevalence of the C677T MTHFR genotype and the contribution of this genotype to hyper-tHcy in patients with IBD. METHODS: Patients with established IBD (n=174) and healthy controls (n=273) were studied. DNA samples were genotyped for the MTHFR (C677T) mutation. Subjects were categorised as homozygous for the thermolabile variant (TT), heterozygous for wild type and variant (CT), or homozygous for the wild type (CC). RESULTS: Plasma homocysteine concentrations were significantly higher in patients with IBD than in healthy controls. A total of 17.5% of ulcerative colitis and 16.8% of Crohn's disease patients were homozygous for the C677T variant compared with 7.3% of controls. Homozygosity (TT) for the variant was associated with higher plasma tHcy levels in patients with IBD and in healthy controls. When all subjects who were TT for the variant were excluded, median plasma tHcy was still significantly higher in IBD than controls. Plasma vitamin B(12) levels were lower in patients with IBD irrespective of MTHFR genotype. CONCLUSIONS: There is an association between the thermolabile MTHFR C677T variant and IBD. This accounts in part for the raised plasma tHcy found in patients with IBD and may contribute to the increased incidence of thromboembolic complications. All patients with IBD should receive low dose folic acid and vitamin B(12) therapy to protect against the thromboembolic complications of raised tHcy.     

Hyperhomocysteinemia and prevalence of polymorphisms of homocysteine metabolism-related enzymes in patients with inflammatory bowel disease

OBJECTIVES: Patients with inflammatory bowel disease (IBD) have an increased risk of thrombotic complications. Moreover, a hypercoagulable state has been hypothesized as a contributing factor in the pathogenesis of IBD. Recently, a growing amount of interest has focused on mild-to-moderate hyperhomocysteinemia as a risk factor for thromboembolic disease. We aimed to evaluate the prevalence of hyperhomocysteinemia in patients with IBD and to investigate the contribution of genetic defects in the enzymes involved in homocysteine (Hcy) metabolism and vitamin status in determining increased levels of plasma total Hcy (tHcy). METHODS: The concentrations of tHcy, folate, and vitamin B12 as well as the prevalence of methylenetetrahydrofolate reductase (MTHFR) 677C to T mutation and the 68-bp insertion at exon 8 of cystathionine beta-synthase (CBS) were measured in patients with IBD and healthy controls. RESULTS: In all, 17 out of 64 IBD patients (26.5%) and four out of 121 (3.3%) controls had hyperhomocysteinemia with a statistically significant difference (p < 0.0001). No significant difference was found between IBD patients and controls with regard to the prevalence of homozygotes for the C677T variant (TT) of MTHFR or the prevalence of heterozygotes for the CBS-gene mutation (IN). Among the IBD patients the only independent factor significantly associated with hyperhomocysteinemia was folate deficiency (p = 0.0002), regardless of the MTHFR or the CBS genotype. CONCLUSIONS: IBD patients have a higher prevalence of hyperhomocysteinemia than do healthy controls. Folate deficiency is the only independent risk factor in developing hyperhomocysteinemia.     

Hyperhomocysteinemia and hypercoagulable state in carotid plaque evolution. Novel risk factors or coincidental risk predictors?

AIM: The majority of patients with carotid occlusive disease (COD) have one or more of the conventional risk factors of atherosclerosis. In addition, hyperhomocysteinemia (HHCY) and hypercoagulable state (HCGS) are increasingly recognized as potentially 'novel' risk factors. The aim of this study was to determine the role of these factors in carotid plaque evolution and clinical manifestation of COD. METHODS: Between September 2003 and 2005, 153 patients were admitted in our Department with clinical and duplex ultrasound evidence of severe (>70%) COD as operative candidates and 33 patients with evidence of moderate (50-69%) stenosis included in the protocol of conservative treatment and lifelong observation. Conventional risk factors of atherosclerotic disease and plasma levels of homocysteine (HCY), fibrinogen (FBG), protein C (PC), protein S, antithrombin III and activated protein C resistance were recorded in all patients. The degree of carotid stenosis was measured in a carotid angiogram following North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria for all operative candidates. Angiographic workup revealed 147 carotid stenoses >70% and 16 internal carotid occlusions in 82 symptomatic and 52 asymptomatic patients, while in 19 patients the carotid stenosis was moderate (50-69%) and these patients included in the conservative treatment group. The study of the 'novel' and conventional risk factors was performed with univariate and multivariate statistical analysis as well as with correlational analysis of HCY and the other risk factors between patients with severe or moderate COD and between symptomatic and asymptomatic patients with carotid stenosis >70%. RESULTS: Our data showed that HHCY was a strong independent risk factor of symptomatic carotid disease >70%. In addition, the coexistence of high FBG levels and thrombophilia factor deficiency with HHCY was significantly related with the clinical manifestation of COD. CONCLUSION: HHCY and HCGS are often detected among patients with severe and symptomatic carotid stenosis. The early diagnosis and treatment of these deficiencies might be helpful for the management of COD, but their role in future clinical practice is yet to be determined.     

Therapy insight: Vascular complications in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) is associated with an increased risk of vascular complications. The most important of these complications are arterial and venous thromboembolism, which represent a significant cause of morbidity and mortality in IBD patients. Recent data suggest that thromboembolism is a disease-specific extraintestinal manifestation of IBD. The most common thrombotic manifestations in IBD are deep vein thrombosis of the leg and pulmonary emboli. It has been suggested that disease activity and the extent of colonic localization are correlated with the risk of developing thromboembolism. The occurrence of thrombosis in patients with IBD is partially attributed to the existing hypercoagulable state in IBD. Both coagulation and fibrinolysis are activated in patients with IBD; this is especially true for those with active disease. The most common risk factors for thrombophilia in IBD patients with venous thromboembolism are Leiden mutation in the gene encoding factor V, hyperhomocysteinemia, and antiphospholipid antibodies. The main genetic defects that have been established as risk factors for venous thrombosis are rather uncommon in IBD, but when present increase the risk of thromboembolism. Screening for coagulation defects seems justified only in IBD patients with a history of thrombosis or a family history of venous thromboembolic events. Antithrombotic treatment of IBD patients with venous thromboembolism is similar to that of thrombotic non-IBD patients.     

THE METHYLENE TETRAHYDROFOLATE REDUCTASE (C677T) MUTATION AS A POTENTIAL RISK FACTOR FOR AVASCULAR NECROSIS IN SICKLE CELL DISEASE

Avascular necrosis (AVN) of the humeral and femoral heads is a frequent and debilitating complication of sickle cell disease. Some of the risk factors for AVN are a-thalassemia and age. Recently, newly discovered thrombophilia mutations have been associated with AVN in patients without sickle cell disease. We studied the frequency of the thermolabile methylene tetrahydrofolate reductase (MTHFR) variant (C677T) in adult sickle cell patients with and without AVN. The frequency of the MTHFR mutation was 35.6% in patients with AVN and 12.9% in those without AVN (p=0.006). These data suggest that the thermolabile MTHFR variant may be a contributing risk factor for AVN in some populations with sickle cell disease.     

The methylene tetrahydrofolate reductase (C677T) mutation as a potential risk factor for avascular necrosis in sickle cell disease

Avascular necrosis (AVN) of the humeral and femoral heads is a frequent and debilitating complication of sickle cell disease. Some of the risk factors for AVN are alpha-thalassemia and age. Recently, newly discovered thrombophilia mutations have been associated with AVN in patients without sickle cell disease. We studied the frequency of the thermolabile methylene tetrahydrofolate reductase (MTHFR) variant (C677T) in adult sickle cell patients with and without AVN. The frequency of the MTHFR mutation was 35.6% in patients with AVN and 12.9% in those without AVN (p = 0.006). These data suggest that the thermolabile MTHFR variant may be a contributing risk factor for AVN in some populations with sickle cell disease.     

Hyperhomocysteinemia increases the risk of venous thrombosis independent of the C677T mutation of the methylenetetrahydrofolate reductase gene in selected Brazilian patients.

Fasting total homocysteine (tHcy) and the methylenetetrahydrofolate reductase (MTHFR) C677T mutation were evaluated in 91 patients with venous thromboembolism and without acquired thrombophilia, and in 91 age-matched and sex-matched controls. Hyperhomocysteinemia was detected in 11 patients (12.1%) and in two controls (2.2%), yielding an odds ratio (OR) for venous thrombosis of 6.1 [95% confidence interval (CI), 1.3-28.4]. After excluding 21 patients and four controls with other known genetic risk factors for venous thrombosis, the OR was not substantially changed (7.0; 95% CI, 1.5-33.1). The prevalence of the MTHFR 677TT genotype was not significantly different in patients (9.9%) and in controls (5.5%), with an OR for venous thrombosis of 1.8 (95% CI, 0.6-5.8). Subjects with the MTHFR 677TT genotype showed higher levels of tHcy compared with the 677CC genotype in patients (P = 0.010) and in controls (P = 0.030). In conclusion, we found that fasting hyperhomocysteinemia is a risk factor for venous thrombosis in patients without known acquired thrombophilia and other genetic risk factors for venous thrombosis. Although tHcy levels are significantly higher in those homozygous for the MTHFR C677T mutation, this genotype does not increase the thrombotic risk in our study population.     

The search for a common thrombophilic state during the active state of inflammatory bowel disease

The clinical course of inflammatory bowel disease (IBD) is frequently associated with thromboembolic complications. The aim of this study was to investigate common thrombophilic markers in Turkish patients with active IBD. Twenty-seven consecutive patients with IBD who were followed-up at the Hacettepe University Hospital were recruited. All the patients were in the active disease state. International normalized ratio, activated partial thromboplastin time, lupus anticoagulant, anticardiolipin IgG, IgM antibodies, protein C, protein S, antithrombin-III, factor V, and factor II mutation of all the IBD patients and of a sex-matched and age-matched control group of non-IBD patients were measured. International normalized ratio, activated partial thromboplastin time, protein C, protein S, lupus anticoagulant, anticardiolipin IgG and IgM, and Proteins C and S mutations were comparable between the 2 groups, but antithrombin-III was significantly lower in the IBD group compared with healthy control group (P<0.0001). As a conclusion, it is reasonable to assume that there may be a subpopulation of the patients with IBD, in whom thrombophilic abnormalities might be important for either disease manifestation or for thrombotic complications. Those hemostatic abnormalities could be either inherited or secondary to the ongoing disease process. Routine screening for the common markers of thrombophilia does not seem to be warranted unless simultaneous arterial and venous thrombosis, major organ thrombosis, strong family history of thrombophilia, unusual and recurrent thrombosis resistant to standard anticoagulant therapy are present. Further studies are definitely required to clarify these complicated associations.     

Factor V Leiden G1691A, prothrombin G20210A, and MTHFR C677T mutations in Turkish inflammatory bowel disease patients

BACKGROUND/AIMS: Patients with inflammatory bowel disease (IBD) have an increased risk for thromboembolic complications. We investigated the incidence of factor V Leiden G1691A, methylene tetrahydrofolate reductase (MTHFR) C677T, and prothrombin G20210A mutation in 27 Turkish IBD patients with no history of thromboembolic disease. METHODOLOGY: Twenty-seven patients, 22 with ulcerative colitis (UC) and 5 with Crohn's disease (CD), and 47 healthy were included to the study. The DNAs were obtained from peripheral blood by using pure polymerase chain kit. Then, factor V Leiden G1691A, which active protein C resistance positive, prothrombin G20210A and MTHFR C677T mutations were investigated in DNA by using LightCycler-Factor V Leiden G1691A mutation, Prothrombin G20210A and MTHFR C677T estimate kits. RESULTS: The heterozygote factor V Leiden G1691A mutation was detected in 3 (11.1%) patients with IBD and 2 (4.3%) controls (p > 0.05). The homozygote factor V Leiden G1691A mutation was not estimated among patients and controls. Heterozygote prothrombin G20210A mutation was detected in 2 (7.4%) patients with IBD and in 0 (0%) controls (p > 0.05). There was no homozygote prothrombin G20210A mutation in IBD and controls. Heterozygote MTHFR C677T mutation was 10 of 27 (37%) patients with IBD while 15 of 47 (32%) controls (p > 0.05). Homozygote MTHFR C677T mutation was detected in 4 patients (14.9%) with IBD and 3 (6.3%) controls (p > 0.05). CONCLUSIONS: Our study did not reveal any association between IBD and the most common hereditary thrombophilic factors and these mutations interfere with neither disease manifestations nor the thrombotic complications.     

肝硬化高同型半胱氨酸血症与MTHFR基因C667T多态性的关系

目的研究肝硬化血浆同型半胱氨酸(HCY)水平及其与N5,N10-亚甲基四氢叶酸还原酶(MTHFR)基因多态性的关系.方法采用柱前衍生化-HPLC方法检测112例健康对照者、87例肝硬化患者血浆同型半胱氨酸的水平,用多聚酶链反应-限制性内切酶片断长度多态性技术(PCR-RFLP)检测其MTHFR基因C667T多态性.结果健康对照组平均血浆HCY浓度为(8.34±3.59)μmol/L,肝硬化组平均血浆HCY浓度为(21.71±4.85)μmol/L.与健康对照组相比,肝硬化组血浆HCY水平显著升高,差异有统计学意义(P＜0.01).PCR-RFLP检测结果发现MTHFR基因型有3种,即纯合子突变TT(+/+)型,杂合子突变TC(+/)型,正常CC(-/-)型.肝硬化组中+/+型、+/型和/-型频率分别为29.9%、52.9%、17.2%;健康对照组分别为19.6%、33.9%、46.4%,两组差异有统计学意义.肝硬化组MTHFR基因突变无论是纯合子还是杂合子突变基因型,其血浆HCY水平均明显高于正常基因型.结论高同型半胱氨酸血症可能是肝硬化的一个危险因素,血浆HCY水平可作为肝硬化的一个辅助诊断指标,MTHFR基因C667T多态性可能是肝硬化高同型半胱氨酸血症的易感基因之一.     

Correlation of polymorphisms to coagulation and biochemical risk factors for cardiovascular diseases

Currently, the established risk factors for cardiovascular disease (CVD) are largely environmental in nature. Conflicting studies have suggested that mutations in specific coagulation genes may also provide a genetic basis for CVD risk. We reviewed clinical studies that examined the role of single nucleotide polymorphisms in coagulation and platelet factors, and a biochemical factor to determine if specific genotypes are correlated with patients with a history of arterial thrombotic diseases (acute coronary syndromes or stroke). A meta-analysis was performed on studies for factors II (G20210A variant), V Leiden (G1691A), VII (R353Q), glycoprotein (GP) IIIa receptor (PI^A1/A2), and methylenetetrahydrofolate reductase (MTHFR, C677T). There was no correlation for factor II or factor V polymorphisms to coronary artery disease (CAD) in 5,607 and 5,431 patients studied, respectively. There was also no correlation for factor II variants and stroke in 3,451 patients studied. For factor V, statistical significance was achieved for the G1691A variant on 3,399 patients with stroke (odds ratio [OR] 1.43, 95% confidence intervals [CI] 1.03 to 1.97). The GP IIIa PI^A1/A2 genotype was associated with increased risk for CAD in 7,920 patients (OR 1.12, 95% CI 1.01 to 1.24), but not for 1,855 patients who had a stroke (OR 0.80, 95% CI 0.62 to 1.04). The combined RQ and RR genotypes of factor VII R353Q were correlated to a reduced risk for CVD in 2,574 patients (OR 0.78, 95% CI 0.65 to 0.93), whereas the QQ genotype had offered more protection (OR 0.53, 95% CI 0.27 to 1.03). The TT homozygous variant of MTHFR was associated with CAD risk in 5,644 patients studied (OR 1.30, 95% CI 1.11 to 1.52) but not for 3,075 patients with stroke. This study shows that for some genes, further studies are unnecessary, whereas for others, no more enrollments are needed. The impact of certain genotypes must be examined in relation to other established risk factors and potentially new therapeutic strategies.     

Fasting, postprandial, and post-methionine-load homocysteinaemia and methylenetetrahydrofolate reductase polymorphism in vascular disease

Hyperhomocysteinaemia is an independent risk factor for cardiovascular disease. The C677T mutation of the methylenetetrahydrofolate reductase (MTHFR) is a common genetic cause of increased homocysteine (HCY) levels. Post-methionine-load HCY concentrations allow identification of certain cases of hyperhomocysteinaemia not demonstrated by fasting levels. This study investigated the relationship between MTHFR polymorphism and (1) fasting HCY levels (77 patients); (2) post-methionine HCY levels (54 patients); and (3) postprandial HCY concentrations (36 patients) in cardiovascular disease. As expected, mean fasting HCY value was higher in the +/+ patients. Moreover, patients who were homozygous for the mutation exhibited significantly increased mean post-methionine-load HCY; in contrast, literature results are conflicting. Mean postprandial HCY, which is not known to be increased in controls, was also increased in the (+/+) patients, although the difference did not reach statistical significance, probably owing to the small size of the sample. MTFHR polymorphism is known to be aggravated by a drop in circulating folate. Additional risk factors may be more prevalent in patients with cardiovascular disease.     

Arg506Gln factor V mutation and Val34Leu factor XIII polymorphism in Finnish patients with inflammatory bowel disease

BACKGROUND: Earlier studies have indicated that inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is associated with thromboembolic complications, whereas inherited disorders of coagulation occur less often than expected in IBD patients. The point mutation Arg506Gln of factor V (Factor V Leiden), resulting in resistance to activated protein C, is the commonest inherited form of thrombophilia. Alterations in circulating levels of factor XIII (FXIII) have been reported among IBD patients. We investigated whether Factor V Leiden or inherited Val34Leu polymorphism of FXIII would associate with IBD or its clinical outcome. METHODS: Factor V Leiden mutation and FXIII Val34Leu polymorphism were assayed in 328 unrelated Finnish patients with UC and 235 patients with CD by solid-phase minisequencing techniques. The control groups comprised 142 apparently healthy Finnish subjects and 120 Finnish blood donors. RESULTS: The frequency of Factor V Leiden mutation among IBD patients (4.5%) was not significantly different from that in subjects living in the same area (2.1%). No significant differences could be observed in the FXIII Val34Leu polymorphism allele frequencies between patients and controls. Clinical features of IBD, including the disease extent, requirement for immunosuppressive drugs, and occurrence of complications, seemed to be independent of these two clotting factor variants analyzed. CONCLUSIONS: Our data do not support an aetiologic or disease-modifying role for the factor V mutation or factor XIII Val34Leu polymorphism in IBD.     

Abdominal venous thrombosis in neonates and infants: role of prothrombotic risk factors - a multicentre case-control study. For the Childhood Thrombophilia Study Group

The factor V (FV) G1691A mutation, the prothrombin (PT) G20210A variant, the methylenetetrahydrofolate reductase (MTHFR) T677T genotype, together with fasting homocysteine (HCY) concentration, lipoprotein (Lp)(a), anti-thrombin (AT), protein C (PC), protein S (PS) and anti-cardiolipin antibodies were investigated in 65 consecutively recruited infants (neonate to < 12 months) with renal venous thrombosis (RVT; n = 31), portal vein thrombosis (PVT; n = 24) or hepatic vein thrombosis (HVT n = 10), and 100 age- and sex-matched healthy controls. FV G1691A was found in 14 babies (heterozygous: RVT n = 9, PVT n = 4; homozygous HVT n = 1) and five controls, the MTHFR TT677 genotype together with increased HCY in four infants with thrombosis (RVT n = 2; PVT n = 1; HVT n = 1) compared with one control, and the PT G20210A variant was present in one control only. PC type I deficiency was diagnosed in three patients (RVT n = 2; PVT n = 1) and AT deficiency in two patients (RVT n = 1; PVT n = 1). Three neonates with spontaneous thrombosis showed FV G1691A combined with Lp(a) and the FV G1691A was combined with the PT G20210A genotype in two infants. Additional triggering factors were reported in 27 patients (41.5%). The overall odds ratios (ORs) and 95% confidence intervals (CIs) with respect to the different thrombosis locations were: RVT (OR/CI: 10.9/3.85-31.1; P < 0.0001), PVT (5.47/1.7-17.6; P < 0.0007) and HVT (3.3/0.58-18.7; P = 0.18). The data presented here suggest that genetic prothrombotic risk factors also play an important role in abdominal venous thrombosis during infancy.     

Prothrombin mutant,factor V Leiden,and thermolabile variant of methylenetetrahidrofolate reductase among patients with sickle cell disease in Brazil

The prevalence of the prothrombin gene variant (allele 20.210 A), factor V Leiden mutation, and homozygosity for transition 677C→T in the methylenetetrahydrofolate reductase (MTHFR) gene was determined among patients with sickle cell disease (SCD). The group included 73 patients with median age of 32.3 years with a diagnosis of sickle cell anemia in 53 patients, hemoglobinopathy SC in 16 patients, and four with S/β⁰ thalassemia. Vascular complications such as ischemic stroke or deep vein thrombosis were diagnosed in nine patients. Heterozygosity for the prothrombin gene variant or factor V Leiden mutation was identified in four patients. However, only one patient, who developed ischemic stroke, was identified as a carrier of factor V Leiden mutation. None of the patients presented homozygosity for the thermolabile variant of the MTHFR. These data suggest a low clinical impact of inherited hypercoagulability risk factors in developing thrombosis, occlusive stroke, or mortality data among patients with SCD in Brazil. Am. J. Hematol. 59:46–50, 1998. © 1998 Wiley-Liss, Inc.     

Hereditary thrombophilia in ethnic Omani patients

Hereditary thrombophilias are a group of inherited conditions that predispose to thrombosis. Mutations like factor V Leiden, prothrombin gene variant 20210A, and hereditary hyperhomocysteinemia are associated with an increased risk for thromboembolism as compared to mutations in natural inhibitors of coagulation. There is also evidence that multiple defects co-exists in persons with a tendency for thrombosis. We studied prothrombotic determinants, namely protein C, protein S, and AT along with factor V Leiden (1691G-->A), prothrombin gene mutation (20210G-->A), CBS 844ins68 mutation, and MTHFR mutation (677C-->T) in consecutive ethnic Omani patients with first episode of a thrombophilic event, namely, deep vein thrombosis (DVT), and/or pulmonary embolism (PE) or thrombosis at an unusual site. Fasting plasma homocysteine was also analyzed. Factor V Leiden and the prothrombin gene mutation were not seen in any patient nor in any control subject studied. The thermolabile MTHFR mutation (677C-->T) was present in 14 patients (35.89%) whereas the CBS 844ins68 mutation was documented in 6 patients (15.38%); 3 patients were common in both groups. Six patients had low protein C (15.38%), two patients had low protein S (5.12%), but none had low AT levels. Interestingly, one patient had triple abnormality, namely, PC deficiency with both CBS 844ins68 mutation as well as the MTHFR mutation (677C-->T) whereas another two patients had the latter two mutations together. This data set, although small, reflects the importance of multiple screening strategies. The yield appears high, emphasizing the referral pattern to a tertiary health center. Of these patients, 43.58% had either or both the hyperhomocysteinemic mutations studied, whereas in 38.46% of these patients, no underlying cause for thrombophilia could be documented.     

The graded effect of hyperhomocysteinemia on the severity and extent of coronary atherosclerosis

It is not clear to what extent methylenetetrahydrofolate reductase (MTHFR) gene and hyperhomocysteinemia effect the severity and extent of coronary atherosclerosis in Asian populations. We examined the MTHFR genotypes and plasma homocysteine (HCY) concentrations in 192 Taiwanese and investigated their relationship with coronary artery disease (CAD), and the severity and extent of coronary atherosclerosis. The distribution of MTHFR genotypes was similar in 116 CAD patients and 76 non-CAD subjects. Homozygosity was noted in 8% of CAD patients and 13% of non-CAD subjects (P=0.33; 95% CI, 0. 2-1.6). The geometric mean of HCY values was higher in CAD patients (11.10+/-1.51 micromol/l) than in non-CAD subjects (9.21+/-1.55 micromol/l) (P=0.003). HCY levels were higher in patients with multi-vessel disease (P<0.05) or in patients with > or = 90% stenotic lesions (P=0.005), compared with non-CAD subjects. The CAD risks in the top two HCY quartiles (> or = 14.0 and 10.1-13.9 micromol/l) were 4.0 (95% CI, 1.7-9.2) and 3.2 (95% CI, 1.4-7.4) times higher than in the lowest quartile (< or = 7.9 micromol/l) (P=0.001 and 0.007, respectively). Linear regression analysis showed significant correlations between HCY concentrations and the severity and extent of atherosclerosis (P=0.0001 for both). In conclusion, hyperhomocysteinemia appears to have a graded effect on the risk of CAD as well as the severity and extent of coronary atherosclerosis. Our findings do not support the homozygous genotype of MTHFR as a genetic risk factor for CAD in this Taiwanese population. Perhaps a further study including assessment of vitamin status is needed to better clarify the relationship between MTHFR genotypes and CAD.     

Haemostasis in inflammatory bowel diseases: clinical relevance

BACKGROUND: In inflammatory bowel disease (IBD), many alterations of haemostasis have been reported. Furthermore. IBD is associated with thromboembolic disease. METHODS: Literature on new insights into the physiology of haemostasis. the interaction between haemostasis and inflammation, plasmatic and mucosal changes in haemostasis in IBD, and haemostasis-interfering therapy in patients with IBD are reviewed. RESULTS: Haemostasis is a vascular-bed-specific, locally regulated, physiological phenomenon aimed at the maintenance of fluidity of blood, and not a simple cascade-shaped chain of reactions. Coagulation activation is part of the inflammatory response, but coagulation activation induces pro-inflammatory effects at the same time. Coagulation and fibrinolysis are activated in the course of IBD. but sometimes in a misbalanced way. Overall, this may induce a state of plasmatic hypercoagulation, irrespective of disease activity. Thromboembolic disease is a common extra-intestinal manifestation of IBD. Established treatment of thromboembolism is similarly useful in IBD patients: concurrent aggressive treatment of exacerbations is recommended. Intractable gastrointestinal bleeding seldom occurs, and has mainly been reported in patients with untreated active IBD. Thrombophilic genetic background does not seem to be responsible for either the increased risk of thromboembolism, or the prevalence of IBD. Haemostasis-interfering therapy to alter the course of IBD is experimental. CONCLUSION: Thromboembolism is an extraintestinal manifestation of IBD, partly because of the associated state of plasmatic hypercoagulation. Thrombophilic genetic background does not contribute to prevalence or course of IBD: genetic investigations may be restricted to patients with clinically proven thrombophilia. Anticoagulant therapy can normally be given to patients. but not as an established therapy against IBD.