Inherited thrombophilia gene mutations are known to have a contributory role in the occurrence of VTE which is clinically manifested by DVT and/or PE [
1]. According to the literature the incidence of VTE varies in different races. There have been several studies with the intention of investigating genetic risk factors contributing to DVT in different populations. Akhter et al. indicated a higher prevalence of 4G allele in patients experiencing DVT in Indian Asian population [
10]. A similar result was also reported by Shammaa et al. in Lebanese population [
20]. In a study on Croatian population by Alfirevic et.al FV Leiden was reported as the highest and prothrombin 20210 as the second most frequent thrombophilia gene mutations [
11]. In this regard, we designed this study to investigate the association of five important polymorphisms with the occurrence of DVT in Iranian patients. The incidence of DVT in our studied population was approximately 2 fold higher in females than in males, a finding consistent with the study of Janbabai et al. on northern Iran which noted that DVT is more prevalent in females [
21]. According to our results FV Leiden, MTHFR C677T, MTHFR A1298C, and PAI
-1 4G/5G mutations were all significantly associated with an increased risk of DVT; but prothrombin 20210 was found in none of the patients and controls. These findings are in agreement with the study of Rahimi et al. who showed that FV Leiden but not Prothrombin 20210 is a risk factor for DVT in western Iran [
22]. In contrast, there are some reports which failed to find the contributory role of FV Leiden on occurrence of DVT in Iranian patients [
23,
24]. In the study conducted by Hajsadeghi et al. FV Leiden and Prothrombin 20210 were introduced as uncommon genetic causes of DVT in Iranian population from Esfahan city. They found no significant association between these two polymorphisms and DVT [
23]. These results were supported by the study of Pourgheysari et al. on VTE in central Iran [
24]. In a Meta analysis study by Simone et al. involving 11,000 cases and 21,000 controls FV Leiden and Prothrombin 20210 were indicated as moderate risk factors of VTE and the risk was increased in heterozygote carriers of FV Leiden or Prothrombin 20210, however they found no significant association with DVT and homozygous pattern of MTHFR C677T [
25]. These contradicting data may reflect the different incidence of various thrombophilia polymorphisms in different populations. Based on studies in different parts of Iran it seems that Prothrombin 20210 is not a significant genetic factor for DVT in Iranian population and there seems to be no consistent findings on FV Leiden.
There are also studies suggesting that combined inheritance of different thrombophilia mutations has a significant effect on the occurrence of DVT [
26,
27], while we did not find statistically significant difference between co inheritance of each two polymorphisms and the single inheritance of the related mutations.
A significant limitation of our study was the lack of data regarding clinical characteristics of the studied population such as localization of DVT and acquired risk factors. Considering that DVT is a multi-factorial disorder arising from acquired and genetic risk factors, it is better to assess both clinical and genetic conditions in DVT patients which lead to a more comprehensive and reliable conception of its etiology.