Vascular Behcet and Mutations in Thrombogenic Genes: Methylene Tetrahydrofolate Reductase, Factor V, and Prothrombin

Vascular Behçet syndrome: from pathogenesis to treatment

Behçet syndrome is a rare, chronic inflammatory disease of unknown aetiopathogenesis, most commonly presenting with mucocutaneous and ocular manifestations. Vascular involvement, most frequently superficial vein and deep vein thrombosis, can occur in up to 50% of patients with Behçet syndrome. Venous thrombosis at atypical sites (inferior and superior vena cava, suprahepatic veins with Budd-Chiari syndrome, portal vein, cerebral sinuses and right atrium and/or ventricle) and arterial involvement (mostly in situ thrombosis and aneurysms of the pulmonary arteries, as well as aneurysms of the abdominal aorta, and peripheral and visceral arteries) are also unique features of Behçet syndrome. Behçet syndrome is considered a natural model of inflammation-induced thrombosis in humans, with an impaired immune-inflammatory response rather than traditional cardiovascular risk factors contributing to thrombogenesis. Specifically, neutrophil hyperactivation and neutrophil-mediated mechanisms of damage directly promote endothelial dysfunction, platelet activation and thrombogenesis in Behçet syndrome. This unusual pathogenesis directly determines the treatment approach, which relies mostly on immunosuppressants rather than anticoagulants for treatment of thrombosis and for secondary prevention. This Review discusses the main histopathological, pathogenetic and clinical aspects of vascular Behçet syndrome, addressing their implications for therapeutic management. Future perspectives in terms of pathogenetic studies, disease monitoring and treatment strategies are also discussed.

Thrombosis in vasculitic disorders-clinical manifestations, pathogenesis and management

Inflammation and coagulation are known to affect each other in many ways. Vasculitis represents a group of disorders where blood vessels (small, medium, large or variable) are infiltrated with inflammatory cells. Accumulating evidence in the literature suggests both clinical and physiological association between vasculitis and thrombosis. Vasculitis-associated thrombosis involves arteries and veins, and a tight connection has been reported between the activity of vasculitis and the appearance of thrombosis. Pathophysiology of these relations is complex and not completely understood. While thrombophilic factors are associated with vasculitis, it remains unclear whether a true association with clinical thrombosis is present. Furthermore, several factors leading to hemostasis, endothelial injury and induction of microparticles were described as possibly accounting for thrombosis. Management of thrombosis in vasculitis patients is challenging and should be further assessed in randomized controlled studies. The current review describes clinical manifestations, pathogenesis and management of thrombosis associated with different vasculitides.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and variations of homocysteine concentrations in patients with Behcet's disease

BACKGROUND

Behcet's disease (BD) is a chronic, relapsing, multi-systemic inflammatory disorder of unknown causes. This disease is mainly characterized by mucocutaneous, ocular, vascular, and central nervous system manifestations. The aim of this study is to investigate the associations between C677T and A1298C polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene and the plasma homocysteine (Hcy), folate, and B12 levels in a relatively large cohort of Tunisian patients with BD.

METHODS

The study included 142 patients with BD and 172 healthy controls. The C677T and A1298C polymorphisms were genotyped using PCR-RFLP. Serum Hcy level was determined using a fluorescence polarization immunoassay. Serum folate and vitamin B12 levels were measured by electrochemiluminescence immunoassay.

RESULTS

Genotype and allele frequencies of the two studied MTHFR polymorphisms did not show any significant differences among BD patients compared to controls. Patient carriers of the 677TT variant and the 677T allele displayed significantly higher Hcy concentration. Moreover, no significant association was found between neither A1298C polymorphism nor the C allele and Hcy, folate, and B12 levels. In multivariate analyses, we reported that 677T allele, male gender, and creatinine level were independent risk factors for hyperhomocysteinemia (HHC).

CONCLUSIONS

In the present study, we report the absence of any significant differences between genotype and allele frequencies for both studied polymorphisms among BD patients compared to healthy controls. Besides, we showed that the T allele of MTHFR C677T polymorphism influenced the Hcy level which is an independent risk factor for HHC in Tunisian BD patients.

Interleukin-2 gene polymorphism in Turkish patients with Behçet's disease and its association with ocular involvement

Behçet's disease (BD) is a chronic immune-mediated systemic disease, characterized by oral and genital lesions and ocular inflammation. Several cytokine genes may play crucial roles in host susceptibility to BD, because the cytokine production capacity varies among individuals and depends on the cytokine gene polymorphisms. The association of the interleukin (IL)-2 gene polymorphisms with the susceptibility to BD was investigated in this study. DNA samples were obtained from a Turkish population of 97 patients with BD and 76 healthy control subjects. Polymorphisms of IL-2 gene at position -330 and +166 were determined using the polymerase chain reaction with sequence-specific primers. In the patients with BD, there was a significantly increased frequency of IL-2 -330 GT genotype. Interestingly, we demonstrated that the frequencies of IL-2 -330 GT and IL-2 + 166 GG genotypes were increased in BD patients with ocular involvement, whilst IL-2 -330 TT genotype was significantly decreased. Also, analysis of allele frequency demonstrated that the presence of G allele at position +166 of IL-2 seems to be a risk factor for ocular involvement. These results reveal that IL-2 -330 GT genotype may be a susceptibility factor for BD, whereas IL-2 -330 TT genotype seems to display a protective association with BD. Additionally, IL-2 gene polymorphisms might be associated with ocular involvement in BD.

Association of allelic variants of factor V Leiden, prothrombin and methylenetetrahydrofolate reductase with thrombosis or ocular involvement in Behçet's disease: a systematic review and meta-analysis

Thrombosis is frequent in patients with Behçet's disease (BD), although the exact cause remains uncertain. Some single nucleotide polymorphism (SNP) (G1691A in factor V gene, also called factor V Leiden [FVL], G20210A in prothrombin gene and C677T in methyltetrahydrofolate reductase [MTHFR] gene) have been associated with thrombosis and ocular involvement in BD with controversial results.

AIM

To assess the effects of FVL, prothrombin and MTHFR SNP variants in patients with BD and thrombosis and ocular involvement by means of a systematic review and meta-analysis.

METHODS

We retrieved studies analyzing the genotype of the above-mentioned polymorphism among patients with BD. A meta-analysis was conducted in a random effects model and calculations of odds ratio (OR) and confidence intervals (CI) were done. Sensitivity analysis and tests for heterogeneity of the results were performed.

RESULTS

27 previous studies analyzed the association of BD and thrombosis with the FVL, prothrombin and MTHFR polymorphisms. A significant association was found between the possession of the AA or GA genotypes of FVL polymorphism among patients with BD and the presence of any thrombosis (OR=2.51; 95% CI: 1.68, 3.74; P<0.00001). In addition, a significant association was found between the possession of the GA or AA genotypes and the presence of BD (OR=2.67; 95% CI: 1.93. 3.72; P<0.00001) when cases with BD and healthy controls were compared. This association was not found when studies from Turkey were excluded. No association was found between prothrombin and MTHFR SNPs and thrombosis in BD, and no association between any SNP and ocular involvement was shown either.

CONCLUSIONS

Factor V Leiden could be responsible for some thrombotic events in at least Turkish patients. However, this relationship has to be demonstrated from a pathogenic point of view.