in 1969 , mccully first proposed homocysteine ( hcy ) to 
 be a cause of cardiovascular disease due to the observation that patients with 
 homocystinuria , a metabolic disease which results in high hcy levels , also 
 displayed atherosclerotic plaques at autopsies . high levels of hcy were associated 
 with endothelial damage and oxidative stress [ 2 , 3 ] . currently , there is a 
 classification commonly used for the degree of hyperhomocysteinemia as follows : 
 normal ( 514 mol / l ) , mild 
 ( 1530 mol / l ) , moderate ( 31100 as many epidemiologic studies supported , mild 
 hyperhomocysteinemia was found risk factor for both venous and arterial 
 thrombosis [ 58 ] . hcy is an 
 intermediary sulphydryl - containing amino acid formed during the conversion of methionine to 
 cysteine . its sulphydryl group can cause direct endothelial cytotoxicity , 
 inhibition of glutathione peroxidase and nitric oxide , interference with 
 clotting factor , and oxidation of ldl . additionally , high levels of hcy 
 cause lipid peroxidation , impaired vasomotor regulation , prothrombic surface , 
 and , therefore , atherothrombogenesis . behcet 's 
 disease ( bd ) , initially described by behcet in 1937 , is a chronic relapsing 
 vasculitis , involving both arteries and veins of various sizes . endothelial dysfunction due to inflammation is considered to be 
 an important factor of thrombosis in bd . some studies have shown that 
 hyperhomocysteinemia might be assumed to be an independent and correctable risk 
 factor for thrombosis in bd [ 1419 ] . moreover , 
 the association between hcy levels and endothelial dysfunction has been shown 
 in patients with bd . however , endothelial injury itself can not clearly 
 account the hypercoagulable status of bd because other vasculitis syndromes do 
 not increase the risk of thrombosis . additionally , existence of several 
 contradictory results with respect to serum hcy levels leads the role of 
 homocysteine in bd unclear . as vitamin b6 , vitamin b12 , and folic acid can 
 decrease homocysteine levels , treatment with these vitamins therefore , it 
 is important to find a clear picture of the role of hcy , which is thought to 
 induce proinflammatory cytokines   during the course of bd . the 
 present study was conducted to evaluate serum hcy as a serological marker for 
 the assessment of the activity of bd with respect to specific individual clinical manifestations . serum levels of hcy were compared with the values of c - reactive protein ( crp ) , 
 an acute phase reactant , the erythrocyte sedimentation rate ( esr ) , and tumor 
 necrosis alpha ( tnf- ) which is an important proinflammatory cytokine . the 
 results were controlled with the healthy individuals . in 
 patients with bd , the question of whether hyperhomocysteinemia depends on the 
 inflammation has not been answered yet . therefore , our aim was to evaluate 
 whether elevated hcy levels , an independent risk factor for both venous and 
 arterial thrombosis , associated 
 with proinflammatory process mediated by cytokines in patients with bd . 70 patients ( 40 males , 30 females ; mean age of 33  7.79 ) fulfilling the international study group criteria 
  for the diagnosis of bd and 33 healthy control subjects ( 17 males , 16 
 females ; mean age of 30  6.68 ) were included in this study . patients with bd 
 were selected from patients who were being followed up by the departments of 
 dermatology and cardiovascular surgery , behcet 's disease unit or referred from 
 other departments . subjects were newly diagnosed or patients who were not 
 taking any medicine regarding bd for some reason . complete blood count , serum 
 glucose , urea , creatinine , total cholesterol , triglyceride , uric acid , alanine 
 aminotransferase , aspartate aminotransferease , alkaline phosphatase , vitamin b12 , and folic acid levels were evaluated in all of the subjects before being 
 included into the study . patients who had other type of illness such as 
 autoimmune disease that could affect the cytokine levels or patients taking any 
 medication affecting the immune system or patients with folic acid or vitamin 
 b12 deficiencies , diabetes mellitus , hyperlipidemia , chronic hepatitis , renal 
 failure , severe psoriasis , pernicious anemia , and chronic alcoholism which 
 might affect hcy levels were excluded from the study . patients taking vitamin 
 supplements in the previous 6 months were also excluded from the study . pathergy test was performed and the number of active 
 manifestations recorded for each patient . since 
 accepted specific clinical activity scoring system and laboratory screening 
 profile for bd has not been performed so far , the activity of patients was 
 considered to have an active disease in case of the existence of two or more 
 symptoms with worsening of clinical symptoms and lack of wellbeing at the time 
 of the study . behcet 's disease 
 activity index ( bdai ) was also performed on our patients according to 
 the method presented by bhakta et al .   and described elaborately 
 by lawton et al . . an 
 overall disease activity scores derived from adding the scores according to the 
 evaluation of the duration of each clinical features ( from 0 to 4 ) and patients 
 and clinicians impressions of the disease activity . as it was agreed that 
 inclusion of erythrocyte sedimentation rate ( esr ) and c - reactive protein ( crp ) 
 measurements would not add significantly to overall measurement of disease 
 activity   and were not included as criteria in bdai [ 26 , 27 ] , 
 esr and crp were not used in the determination of the activation of the 
 disease . the patients who had no symptoms regarding bd in four weeks period or 
 less than two symptoms with a healing process and an overall wellbeing status 
 were grouped in inactive bd . either venous or arterial system involvement was 
 defined as present when confirmed by doppler ultrasonography , radioisotope 
 venography , magnetic resonance angiography , conventional angiography , or computerized 
 tomography . serum homocysteine levels in the study groups were determined by fluorescence 
 polarization immunoassay ( fpia ) technique ( axis biochemicals , asa , oslo , 
 norway ) . the 95% confidence interval of plasma hcy 
 level suggested by the manufacturer for healthy individuals is 4.4512.42 mol / l and 
 serum hcy level is expected to be up to 10% higher than ethylenediamine 
 tetraacetate ( edta ) plasma . five 
 cc blood samples were drawn using a 25 gauge needle from a peripheral 
 vein , avoiding haemolysis in the morning hours after an overnight fasting and 
 30 minutes of supine rest and collected into 10 ml empty evacuated tubes without 
 edta , heparin , or clot activators . the serum was separated in aliquots and immediately frozen and stored 
 at 80c within 60 minutes until use . the tnf- level was measured with an enzyme - linked immunosorbant assay ( elisa ) kit 
 ( bender medsystems , vienna , austria , lot # 223/208-d1 ) 
 with a detectable level set at 14 pg / ml . five cc serum was separated by 
 centrifugation at 1000  g for 10 minutes and stored at 70c until use . crp was measured by a highly sensitive turbidimetric method using conventional 
 biochemical automatic analyzer . each variant was evaluated by one sample 
 kolmogorov - smirnov test for compatibility 
 with normal distribution . as the data did not fit normal distribution , the 
 nonparametric kruskall - wallis test for intergroups comparison and mann - whitney 
 u test or bonferroni corrected mann - whitney u tests were used for between - group 
 comparisons as indicated . levels of significance set at 
 0.05 but in bonferroni corrected test the significance threshold of 0.05 
 yielded to the value of 0.0167 . data are presented as median values and their 
 individual ranges ( in parenthesis ) . detected number of patients suffering from individual active clinical manifestations of 
 the disease in various degrees was 31 with oral ulceration ( 44.28% ) , 23 with genital ulceration 
 ( 32.85% ) , 18 with ocular involvement ( 25.71% ) , 37 with vascular involvement ( 52.85% ) , 
 25 with arthritis ( 35.71% ) , and 31 with cutaneous lesions like erythema nodosum 
 ( en ) and papulopustular eruption ( ppe ) ( 44.28% ) . thirty five patients ( 50% ) 
 were found to have positive pathergy test . according to our evaluation scale , 34 
 patients were considered to have active disease with a median of 4 symptoms ranging between 
 2 and 5 and 36 patients to have inactive disease with a median of 1 symptom 
 ranging between 1 and 2 . consistently , active group had a statistically 
 significant high bdai score with a median of 16 ranging between 9 and 25 
 compared to inactive group with a median of 2 ranging between 1 and 5 ( p = .00 ) 
 ( table 1 ) . according to vascular examination , venous involvement ( deep venous thrombosis 
 with or without thromboflebitis ) was found in 23 patients and either arterial 
 occlusion or aneurysm was found in 14 patients in active group . 17 patients in 
 inactive group had short duration of thromboflebitis with a wellbeing status . in intergroup comparison of active bd , inactive bd , and healthy controls according to serum 
 levels of hcy , tnf- , crp , and esr significant difference was detected for 
 each parameter ( p = .00 for each parameter ) ( table 1 ) . to determine which 
 group / groups cause the difference , between - group comparisons performed . 
 according to this , hcy , tnf- , crp , and esr levels were found elevated in 
 active bd compared to inactive bd and healthy controls . hcy , tnf- , crp , and 
 esr levels of inactive bd were found elevated compared to healthy controls . hcy 
 and tnf- suggested having a strong association of disease activity ( table 1 ) . hcy and tnf- were found to have high correlation with bdai scores ( r = 0.836 , p = .00 
 and r = 0.924 , p = .00 , resp . ) and the number of active clinical 
 manifestations increased ( r = 0.694 , p = .00 and r = 0.842 , p = .00 , resp . ) 
 while esr and crp also showed a positive correlation with both parameters with 
 relatively less significance ( table 2 ) . the evaluation of association between specific individual clinical manifestations 
 and serum levels revealed increased hcy levels in patients with oral ulcer ( p = .03 ) , 
 genital ulcer ( p = .005 ) , the presence of positive pathergy test ( p = .007 ) , 
 ocular lesion ( p = .00 ) , and vascular lesion of high significance ( p = .00 ) 
 ( table 3 ) . the serum levels of tnf- were found to have strong association with oral ulcer ( p = .00 ) , 
 genital ulcer ( p = .00 ) , the presence of positive pathergy test ( p = .00 ) , 
 ocular lesion ( p = .00 ) , and vascular lesion ( p = .000 ) ( table 4 ) . no 
 association was found between tnf- levels 
 and en / ppe and arthritis . the association of crp with genital ulcer ( p = .001 ) , ocular lesion ( p = .001 ) , 
 vascular lesion ( p = .001 ) , en / ppe ( p = .043 ) , and the presence of 
 positive pathergy test ( p = .016 ) was found . no association was found between crp levels and ocular lesion and 
 arthritis ( table 5 ) . esr showed no significant association with any of the 
 specific individual clinical manifestations ( table 6 ) . a significant positive correlation was found between serum hcy and tnf- levels 
 ( r = 0.89 , p = .00 ) , crp ( r = 0.645 , p = .00 ) and esr ( r = 0.561 , p = .00 ) 
 ( table 2 ) . among parameters , hcy was found to be the best predictor of tnf- which 
 was used as a dependent variable ( beta = 6.45 , r = 0.88 , p = .00 ) ( table 7 ) . serum levels of hcy in active bd patients with vascular involvement were found 
 significantly increased when compared in patients with active bd without 
 vascular involvement . in addition , serum levels of hcy in inactive bd with 
 vascular involvement were found significantly increased compared to inactive bd 
 ( table 8) . serum levels of active bd patients with vascular involvement , oral ulcer , arthritis / arthralgia , 
 en / ppe and the presence of positive pathergy test were found significantly 
 increased compared to inactive bd patients with the same clinical symptoms 
 ( table 9 ) . the main 
 pathology in bd is an inflammatory process of small arteries and veins and 
 thrombosis as a result of vasculitis of the vaso vasorum . hyperhomocysteinemia 
 has been shown to be a risk factor for thrombosis in bd in some recent studies [ 1419 ] . in our study , 
 serum levels of hcy were found to have a positive correlation with bdai scores 
 and total number of active clinical manifestations . we also found significantly 
 elevated levels of serum total hcy in active bd when compared with inactive and 
 control groups . our 
 results supported that total serum hcy was a reliable marker for the activity 
 of disease . aksu et al .   divided their patients with bd into two 
 groups on the basis of thrombosis and they found hyperhomocysteinemia in 
 patients with a history of thrombosis . could not 
 find different serum total hcy levels between patients with and without a 
 history of thrombosis . the main limitations of this study were its 
 retrospective nature and the long lag period between the thrombotic events and 
 the time of analyses performed . evaluated their patients with 
 respect to current clinical activity and 10 patients were accepted as 
 clinically active , though they could not find association between serum hcy levels 
 and disease activity . the main factor responsible for the increased frequency of thrombosis in bd is thought 
 to be endothelial dysfunction caused by vascular inflammation [ 14 , 15 ] . the 
 association between hcy levels and endothelial dysfunction and its correlation 
 to the degree of endothelial damage has been shown in patients with bd . hcy generates superoxide and hydrogen peroxide , both 
 of which have been linked to endothelial damage . hcy - induced vascular 
 problems are thought 
 to be multifactorial , including direct hcy damage to the endothelium , enhanced 
 lipid peroxidation and increased platelet aggregation by the effects on the 
 coagulation system [ 15 , 17 ] . in our study , the evaluation of association between specific individual clinical 
 manifestations and serum levels revealed increased hcy levels in patients with 
 oral ulcer , genital ulcer , the presence of positive pathergy test and 
 particularly with ocular and vascular lesions of high significance . er et al .   showed the association of hcy levels with disease 
 activity and ocular bd . however , they could not find 
 statistically significant difference between active and inactive diseases and association 
 with mucocutaneous involvement in bd . on the other hand , korkmaz et al . reported 
 no statistically significant association between vascular involvement and 
 homocysteine levels , though 50% of patients with vascular involvement had 
 hyperhomocysteinemia . although the mechanism is unknown , all these findings 
 indicate that hcy associates with bd . however , the causes of these different 
 study outcomes are not clear . the different sample sizes , different disease 
 durations or study patients under treatment that might affect outcomes might 
 have contributed . in addition , the question whether hyperhomocysteinemia depends 
 on the inflammation or not remains to be unanswered . although the etiopathogenesis of bd has not yet been clarified , different immunological 
 abnormalities have been reported and increased spontaneous secretion of tnf- , 
 interleukin-6 ( il-6 ) , and interleukin-8 ( il-8 ) in monocyte cultures obtained 
 from bd patients . necrotizing , neutrophilic ( leukocytoclastic ) 
 obliterative perivasculitis , and venous thrombosis with lymphocytic and 
 monocytic cellular infiltration of the veins , capillaries , and the arteries of 
 all sizes and endothelial dysfunction are the hallmarks of bd . histopathological 
 studies revealed cellular infiltration consisting of lymphocytes , plasmocytes , 
 monocytes , and peripheral polymorphonuclear leukocytes ( pmns ) in varying degrees , depending on the 
 stage of lesion in bd [ 30 , 31 ] . since cytokines are involved in the regulation 
 of functions of lymphocytes and phagocytes , they are playing important role in 
 the pathogenesis of the disease [ 30 , 31 ] . although any organ system may be 
 affected , there is high prevalence of venous or arterial thrombosis in bd and 
 most clinical features are associated with systemic vasculitis . it has been 
 suggested that vasculo - behcet disease should be classified as a neutrophilic 
 vasculitis targeting the vaso 
 vasorum . aneurysm formation may be related to degeneration of arterial 
 wall caused by inflammation of the vaso vasorum . as hcy has profound effects concerning vascular 
 lesions and thrombosis , vascular and ocular involvements in bd deserve special 
 attention . indeed , we found significantly elevated levels of hcy with respect 
 to the presence of vascular involvement in the intragroup comparisons of separately 
 active and inactive bd patients . however , 
 in our study hcy was found to be able to evaluate the fluctuating activity of 
 disease in an objective fashion and the number of additional organ systems 
 affected . this finding may imply that hcy can not simply be assumed to be an 
 independent risk factor for only vascular and ocular vaso - occlusive diseases in 
 bd [ 1419 ] . that is because most clinical features are thought 
 to be associated with systemic vasculitis and dermal blood vessels embolized by 
 thrombus are observed even at the sites of needle - prick reaction . furthermore , endothelial injury is a characteristic finding in bd and can be 
 observed even in patients without any clinical vascular involvement [ 24 , 33 , 34 ] . these data provides 
 insight as to why hcy is able to detect overall disease activity 
 with respect to different system involvements and why ascribed significance of 
 hcy is not limited only to the individual clinical manifestations of vascular or 
 vaso - occlusive ocular involvements ? consistently , we found the association of 
 hcy not only   with vascular and ocular vaso - occlusive 
 disease but also with genital ulceration , positive pathergy test , and oral 
 ulcers in bd patients , though with less significance . therefore , our results not only support the 
 suggestion that hcy is a risk factor for vascular and ocular vaso - occlusive 
 diseases in bd [ 15 , 16 ] but also identify hcy as a risk factor for the 
 development of most clinical features that are known to be associated with 
 vasculitis . we found a significant positive correlation between serum hcy , tnf- and crp levels , 
 and esr with relatively less significance . hcy was found to be the best 
 predictor of tnf- among other parameters . in other words , hcy was found to 
 explain 88% of tnf- change while crp and esr were found to explain 39% and 14% 
 of tnf- change , respectively . the significance of hcy in bd represents either vascular endothelium damaged by hcy or immune system 
 stimulation by hcy , our study may demonstrate the link between hcy and 
 inflammation pathways in bd . although there are conflicting results in the literature with 
 respect to the reliability of esr and crp as markers to detect 
 the activity of bd and they are currently not involved as criteria in bdai 
 scores , crp deserves special attention because it has a strong predictive 
 power of vascular events . we found both of them were elevated in the 
 active stage of the disease . however , unlike crp , esr showed no significant 
 association with any of the specific individual clinical manifestations . 
 relatively large sample size of our patients with vascular involvement might be 
 a factor affecting our study outcome in favor of the significance of crp in bd . chemotactic and phagocytic activities 
 of neutrophils in patients with bd have been reported to be high   and tnf- is a major factor 
 modulating inflammatory responses which is known to be increased in 
 inflammatory diseases . recent studies showed increased tnf- level in bd patients , 
 especially in the exacerbation period [ 24 , 30 ] . synthesis of crp in the liver 
 is induced by several proinflammatory cytokines including tnf-. this marks crp 
 as a precise objective index of inflammatory activity and surrogate of 
 underlying cytokine stimulus and a sensitive marker of underlying systemic 
 inflammation . it has been demonstrated that coagulation indices including 
 fibrinogen , von willebrand factor , and plasminogen activator activity are 
 increased in bd and hcy is thought to promote the clotting cascade via several 
 actions including inactivation of protein c , activation of coagulation factor 
 v , increased vascular smooth muscle cell proliferation , and inhibition of 
 thrombomodulin . hcy is thought to induce proinflammatory 
 cytokines [ 24 , 3638 ] . in 
 vasculitis such as bd , endothelial - leukocyte interaction is an important part 
 of the inflammation   and hcy has been reported to increase endothelial - leukocyte 
 interaction . hcy has been shown in vivo and in vitro to promote inflammatory 
 process such as the adhesion of neutrophils to endothelial cells as well as the 
 release of the inflammatory cytokine il-8 and monocyte chemoattractant 
 protein-1 ( mpc-1 ) . hcy was shown to enhance the cytokine - stimulated 
 expression of endothelial cell adhesion molecules and monocyte and t - cell 
 adhesion to endothelial cells . adhesion molecules are characterized not only by their ability 
 to cause directed migration of leukocytes into inflamed tissue , but they may 
 also have biological effects on other cell types , such as endothelial cells , 
 fibroblasts , and smooth muscle cells . hcy was shown to promote tnf- 
 mediated induction of vascular cell adhesion molecule-1 ( vcam-1 ) in endothelial 
 cells . with respect to innate inflammatory markers such as tnf- and crp , 
 serum hcy has been shown to contribute to innate immune response and to be a 
 determinant of tnf- in hypertensive patients . in addition , hcy has been 
 shown to enhance inflammation markers in murine models . the correlation of 
 hcy levels with nitric oxide has been shown in patients with bd . hcy is 
 known to increase nitric oxide production in vascular smooth muscle cells and nitric 
 oxide is known to be released as a response to systemic immunoinflammatory 
 diseases . a study demonstrated that targeting the tnf pathway 
 significantly decreased hcy and crp levels in patients with psoriatic arthritis 
 and in this study , crp showed a positive correlation with hcy at baseline . hcy has been suggested to 
 be related to the markers of inflammation and its elevated levels as a result 
 of immunosuppressive treatment . this is the reason why we studied 
 with the patients who were not taking any medication regarding bd . this definite 
 selection decreased the number of our study population as a study limitation . 
 in our study , serum levels of active bd patients with vascular involvement , 
 oral ulcer , arthritis / arthralgia , en / ppe and the presence of positive pathergy 
 test were found significantly increased compared to inactive bd patients with 
 the same clinical symptoms . therefore , serum levels of hcy were 
 found to explain the wide clinical spectrum of the activity of the specific 
 individual symptoms . in summary , hcy 
 and crp have effects into the mechanism linking inflammation and coagulation 
 and hcy is thought to induce proinflammatory cytokines including tnf- , which 
 is known to increase chemotactic and phagocytic activities of neutrophils , endothelial - leukocyte 
 interaction , and crp levels . we found a high correlation between serum levels 
 of hcy and tnf- and hcy was found to explain the wide clinical spectrum of the 
 activity of the disease and specific individual symptoms . taking all these 
 findings into account , a theory might be put forward which is open to further 
 in vivo and in vitro studies ; hcy - induced inflammation may be responsible for 
 tissue damage as well as endothelial dysfunction in bd and enhanced hcy may 
 account for the differences observed between clinically distinct subgroups . lowering hcyby selected vitamin supplements or tnf blockade may be the future 
 direction of prevention from developing the risk of thrombosis and vasculitis 
 of different organ systems and thereby activation of bd disease . our data identified hcy as a risk factor for the 
 development of not only vascular and ocular involvement but also most clinical 
 features that are known to be associated with vasculitis in bd . in addition , serum 
 hcy showed a strong association of disease activity and correlated with bdai 
 scores and the number of active clinical manifestations increased . therefore , hcy might be assumed as a reliable 
 marker for the activity of disease . hcy was found to be the best predictor of 
 tnf- and positively correlated with inflammatory markers . our findings 
 suggest that hcy might contribute to the pathogenesis of bd by inducing 
 inflammation . further investigation in clinical and experimental studies is required to 
 conclusively demonstrate the association between hcy and inflammatory pathways .
objective . our aim was to evaluate the significance of homocysteine ( hcy ) in behcet 's disease ( bd ) and the association of elevated hcy levels associated with the indices of inflammation in bd . 
 methods . 
 untreated 70 patients with bd and 33 healthy individuals were included into the study . 
 hcy , tumor necrosis alpha ( tnf- ) , c - reactive protein ( crp ) , and erythrocyte sedimentation rate ( esr ) were evaluated with respect to activity and specific individual clinical manifestations of the disease . 
 results . 
 hcy levels were found significantly elevated in active bd when compared to inactive bd and healthy controls . 
 hcy levels were found to have high correlation with the number of active clinical manifestations increased . 
 a significant positive correlation was found between serum hcy and tnf- levels , crp , and esr . 
 hcy was found to be the best predictor of tnf- among other parameters . 
 conclusion . 
 hcy may involve in the pathogenesis of bd by inducing inflammation .