Hoţoleanu Cristina, Porojan-Iuga M, Rusu M L, Andercou A
Medical Clinic II, University of Medicine and Pharmacy, Iuliu Haţieganu, Cluj-Napoca, Romania.
Rom J Intern Med. 2007;45(2):159-64.
Hyperhomocysteinemia, considered "the cholesterol of nineties", is an established risk factor for cardiovascular diseases and premature atherosclerosis. Hyperhomocysteinemia is due to genetic and acquired factors (unhealthy lifestyle with poor diet in folate and vitamin B, elderly, renal impairment, thyroid diseases, malignancies). More recently, hyperhomocysteinemia was associated with venous thrombosis. Several studies found a correlation with a usual site of thrombosis (central retinal vein, mesenterical level, cerebral veins, Budd-Chiari syndrome). Other studies showed the association between hyperhomocysteinemia and recurrent venous thrombosis. This condition is of high interest because homocysteine may represent a potentially reversible cause of thrombophilia. Although methylenetetrahydrofolate reductase (MTHFR) C677T genotype and deficits of folic acid, vitamin B12 lead to hyperhomocysteinemia, in cases with a thrombotic event the correlations between homocysteine level and folic acid as well as between homocysteinemia and vitamin B12 were found to be weak and no significant correlation between homocysteinemia and MTHFR was identified. Recently, some authors reported an independent association between low levels of folic acid or vitamin B12 and venous thrombosis. Regarding the MTHFR genotype, the risk for venous thrombosis is increased only in patients with factor V Leiden. A recent meta-analysis of 24 retrospective and 3 prospective studies published in electronic literature showed that a 5 micromol/L higher homocysteine level was associated with a 27% (95% CI: 1-59) higher risk of venous thrombosis in prospective studies and a 60% (95% CI: 10-134) higher risk in retrospective studies. A meta-analysis of the short-term trials of therapy with folic acid showed a reduction of 25% of homocysteinemia and a further reduction of 7% when vitamin B12 was associated. This situation may be associated with a 10% to 20% decreased risk of venous thrombosis. Further trials are required to estimate if this is worthwhile from the clinical point of view. In medical practice the measurement of homocysteinemia may be indicated in unexplained idiopathic venous thrombosis, or recurrent episodes or venous thrombosis occurred at an early age or at an uncommon site.
高同型半胱氨酸血症被视为“90年代的胆固醇”，是心血管疾病和过早动脉粥样硬化的既定危险因素。高同型半胱氨酸血症归因于遗传和后天因素（不健康的生活方式，饮食中缺乏叶酸和维生素B，老年人，肾功能损害，甲状腺疾病，恶性肿瘤）。最近，高同型半胱氨酸血症与静脉血栓形成有关。多项研究发现其与血栓形成的常见部位（视网膜中央静脉、肠系膜水平、脑静脉、布加综合征）存在关联。其他研究显示高同型半胱氨酸血症与复发性静脉血栓形成之间存在关联。这种情况备受关注，因为同型半胱氨酸可能是血栓形成倾向的一个潜在可逆原因。虽然亚甲基四氢叶酸还原酶（MTHFR）C677T基因型以及叶酸、维生素B12缺乏会导致高同型半胱氨酸血症，但在发生血栓事件的病例中，发现同型半胱氨酸水平与叶酸之间以及高同型半胱氨酸血症与维生素B12之间的相关性较弱，且未发现高同型半胱氨酸血症与MTHFR之间存在显著相关性。最近，一些作者报告了低水平叶酸或维生素B12与静脉血栓形成之间的独立关联。关于MTHFR基因型，仅在携带因子V莱顿突变的患者中静脉血栓形成风险增加。最近对电子文献中发表的24项回顾性研究和3项前瞻性研究进行的荟萃分析表明，在前瞻性研究中，同型半胱氨酸水平每升高5微摩尔/升，静脉血栓形成风险高27%（95%CI：1-59），在回顾性研究中高60%（95%CI：10-134）。对叶酸治疗短期试验的荟萃分析显示，高同型半胱氨酸血症降低了25%，当联合维生素B12时进一步降低7%。这种情况可能使静脉血栓形成风险降低10%至20%。从临床角度来看，是否值得还需要进一步试验来评估。在医学实践中，对于不明原因的特发性静脉血栓形成、复发性发作或在早年或不常见部位发生的静脉血栓形成，可能需要检测高同型半胱氨酸血症。
