Thermolabile MTHFR genotype and retinal vascular occlusive disease

Methylenetetrahydrofolate reductase polymorphisms as risk factors for retinal venous occlusive disease: A literature review

The role of polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene in retinal vein occlusion (RVO) is a theme of discussion since the first reports of RVO in patients with MTHFR C677T mutation and without classic acquired risk factors for retinal vascular disease. The association between MTHFR polymorphisms and RVO has been studied over the last 20 years producing conflicting results. This review aims to summarize the literature concerning the role MTHFR polymorphisms as risk factors for RVO.

Association of retinal vein occlusion, homocysteine, and the thrombophilic mutations in a Turkish population: A case-control study

PURPOSE

To compare homocysteine and thrombophilic mutations for the methylenetetrahydrofolate reductase (MTHFR) C677T, factor V Leiden, and prothrombin G20210A between retinal vein occlusion (RVO) and healthy controls in a Turkish population.

MATERIALS AND METHODS

Forty-nine subjects with RVO were compared for homocysteine status and the MTHFR C677T, prothrombin G20210A, and factor V Leiden mutations with those of 68 healthy controls. Then, the groups were subdivided into two subgroups according to age (less than 50 years old, equal to or more than 50 years old) and were further compared.

RESULTS

Mean plasma level of homocysteine was similar, but the frequency of hyperhomocysteinemia was significantly higher in the RVO group when compared with the control group (22.5% and 8.8%, respectively, p = 0.037). The frequency of all thrombophilic mutations was similar between the groups (p > 0.05). The frequency of all thrombophilic mutations and homocysteine levels was also similar between age subgroups (p > 0.05). Only hyperhomocysteinemia was significantly different between subgroups (p = 0.037); the frequency of hyperhomocysteinemia was significantly different in RVO patients less than 50 years old (22.7%) from that in healthy controls less than 50 years old (11.1%). Two RVO patients (4.1%) with bilateral involvement had MTHFR C677T mutation.

CONCLUSIONS

Screening for thrombophilic mutations such as MTHFR C677T, factor V Leiden, and prothrombin G20210A in RVO patients at all ages seems to be unnecessary and not cost-effective. However, thrombophilic disorders should be screened selectively, focusing on young individuals, especially with bilateral involvement, without additional cardiovascular risk factors, or a family history of thrombosis.

NONICHEMIC CENTRAL RETINAL VEIN OCCLUSION ASSOCIATED WITH HEREDITARY THROMBOPHYLIA

Retinal vein occlusion (RVO) is the second most common retinal vein disease with significant visual loss via thrombus or compression of vein wall. Thrombophilia is the predisposition to vascular thrombosis with the existence of genetic defect that leads to blood hypercoagulability. This report describes the case of a 55 year old male patient, with an active life who presented himself at the emergency room with acute visual lose, insidious and progressive visual field constriction, without any known history of neurological or vascular diseases. The examinations revealed unilateral optic nerve head edema, the fluorescein angiography was specific for nonischemic central retinal vein occlusion CRVO complicated with macular edema. Blood examinations has emphasized the presence of the heterozygous mutation A1298C in the methylenetetrahydrofolate reductase gene (MTHFR), the only one presented from the thrombophilia screen panel and a slightly elevated cholesterol level. During the follow-up period, the patient received anti-VEGF treatment (Bevacizumab, 3x 0.1 ml intravitreal injections) with improved visual acuity and amendment of macular edema. The complex etiology calls for interdisciplinary approach to determine better the cause of this ophthalmological disease. Although studies have found a correlation between some thrombophilia mutations and retinal vein occlusion, more studies that contain a larger number of patients are necessary in order to determine the final role of these gene variants.

Hyperhomocysteinia is a risk factor for retinal venous occlusion: a case control study

BACKGROUND

We evaluated the role of hyperhomocysteinemia as a risk factor for retinal vein occlusion (RVO) in Indian patients.

TYPE OF STUDY

Matched case control type of longitudinal study was conducted in 2006-2007.

MATERIALS AND METHODS

Two medical retina specialists examined the eyes having an event of RVO in the last 15 days. A similar number of eyes without RVO were also examined. The serum and urine homocysteine levels of these persons were tested. Matched pair analysis was carried out to determine the risk of RVO among those with hyperhomocysteinemia.

RESULTS

We included 20 cases of RVO and 20 age- and sex-matched persons without RVO. The risk of RVO was significantly higher in persons with hyperhomocysteinemia [difference of mean 31.62 μmol/L (95% Confidence Interval 16.60-47 . 86), P = 2.1 × 10-13 ]. The mean urine homocysteine level among cases and controls was not statistically significant. There were 12 persons with hypertension in both cases and control groups.

CONCLUSION

Hyperhomocysteinemia is a risk factor for RVO. Any list of investigations for a case of RVO should include total plasma homocysteine (tHcy) levels.

Methylenetetrahydrofolate reductase C677T mutation and risk of retinal vein thrombosis

BACKGROUND

Elevated plasma homocysteine (Hcy) level has been established as a significant risk factor for venous thrombosis and cardiovascular disease. Homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation has been associated with elevated plasma Hcy concentration and may contribute to retinal vein thrombosis (RVT) development. The aim of the present study was to investigate whether the hyperhomocysteinemia and/or homozygosity for the MTHFR C677T mutation are associated with an increased risk for RVT.

MATERIALS AND METHODS

Our study population consisted of 73 consecutive patients (50-78 years old) with RVT and 73 control subjects (51-80 years old), matched for age and sex. Genotyping for the MTHFR C677T mutation was performed by polymerase chain reaction-restriction fragment length polymorphism technique and Hcy level was determined by an enzyme immunoassay kit.

RESULTS

The prevalence of 677TT genotype was higher in patients than control subjects, but the difference in frequency didn't reach a significant value (P = 0.07). The frequency of the 677T allele was 26% and 21.2% in patients and controls, respectively and did not differ significantly between the two groups (odds ratio = 1.3, 95% confidence interval (0.75-2.24), P = 0.33). Fasting plasma total Hcy level was significantly higher in patients than controls (P = 0.001).

CONCLUSION

Our study demonstrated that hyperhomocysteinemia, but not the MTHFR C677T mutation, is associated with RVT.

Genetic polymorphisms associated with retinal vein occlusion: a Greek case-control study and meta-analysis

BACKGROUND

The genetic background of retinal vein occlusion (RVO) remains unclear. In the current study, we aimed to replicate polymorphisms related to thrombophilia/hypofibrinolysis in a Greek population and also systematically summarize current evidence available on the topic.

MATERIALS AND METHODS

A total of 48 RVO patients and 53 controls were genotyped for factor V H1299R and V Leiden, β-fibrinogen G455A, PAI-1 4G/5G, ACE I/D, HPA1, prothrombin G20210A, factor XIII Val34Leu, MTHFR A1298C and C677T polymorphisms. We examined the association between RVO and the above polymorphisms under a per-allele genetic model in a Greek unrelated case/control population. Additionally, searching PubMed up to January 2012, we identified existing evidence on these polymorphisms and performed meta-analyses.

RESULTS

A total of three polymorphisms had nominally significant associations with RVO. These associations pertained to ACE D allele (odds ratio, OR, 2.08 [95% CI, 1.12-3.85], p = 0.02); factor XIII 34Leu allele (OR = 0.41 [95% CI, 0.18-0.95], p = 0.037] and MTHFR 677T variant (OR = 2.20 [95% CI 1.10-4.40], p = 0.026). We performed a meta-analysis on the associations between RVO and PAI-1 (n = 5), factor V Leiden (n = 21), MTHFR C677T (n = 19) and prothrombin G20210A (n = 21). We observed nominally significant associations only for PAI-1 (OR = 1.27 [95% CI, 1.02-1.60, p = 0.036]) (I(2) = 44.7%), and factor V Leiden (OR = 1.40 [95% CI, 1.07-1.84, p = 0.015]) (I(2) = 3.6%) using random effects model.

CONCLUSIONS

Our results suggest that there may be an association between increased risk for RVO and ACE I/D, MTHFR C677T, PAI-1 4G/5G and factor V Leiden polymorphisms, whereas the Val34Leu variant may exert a protective effect.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism, and risk of retinal vein occlusion: a meta-analysis

OBJECTIVE

To assess the role of plasma total homocysteine (tHcy) concentrations and homozygosity for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) C677T gene as risk factors for retinal vascular occlusive disease.

DESIGN

Retinal vein occlusion (RVO) is an important cause of vision loss. Early meta-analyses showed that tHcy was associated with an increased risk of RVO, but a significant number of new studies have been published.

PARTICIPANTS AND/OR CONTROLS

RVO patients and controls.

METHODS

Data sources included MEDLINE, Web of Science, and PubMed searches and searching reference lists of relevant articles and reviews. Reviewers searched the databases, selected the studies, and then extracted data. Results were pooled quantitatively using meta-analytic methods.

MAIN OUTCOME MEASURES

tHcy concentrations and MTHFR genotype.

RESULTS

There were 25 case-control studies for tHcy (1533 cases and 1708 controls) and 18 case-control studies for MTHFR (1082 cases and 4706 controls). The mean tHcy was on average 2.8 micromol/L (95% confidence interval [CI], 1.8-3.7) greater in the RVO cases compared with controls, but there was evidence of between-study heterogeneity (P<0.001, I(2) = 93%). There was funnel plot asymmetry suggesting publication bias. There was no evidence of association between homozygosity for the MTHFR C677T genotype and RVO (odds ratio [OR] 1.20; 95% CI, 0.84-1.71), but again marked heterogeneity (P = 0.004, I(2) = 53%) was observed.

CONCLUSIONS

There was some evidence that elevated tHcy was associated with RVO, but not homozygosity for the MTHFR C677T genotype. Both analyses should be interpreted cautiously because of marked heterogeneity between the study estimates and possible effect of publication bias on the tHcy findings.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Branch retinal vein occlusion: pathogenesis, visual prognosis, and treatment modalities

In branch retinal vein occlusion (BRVO), abnormal arteriovenous crossing with vein compression, degenerative changes of the vessel wall and abnormal hematological factors constitute the primary mechanism of vessel occlusion. In general, BRVO has a good prognosis: 50-60% of eyes are reported to have a final visual acuity (VA) of 20/40 or better even without treatment. One important prognostic factor for final VA appears to be the initial VA. Grid laser photocoagulation is an established treatment for macular edema in a particular group of patients with BRVO, while promising results for this condition are shown by intravitreal application of steroids or new vascular endothelial growth factor inhibitors. Vitrectomy with or without arteriovenous sheathotomy combined with removal of the internal limiting membrane may improve vision in eyes with macular edema which are unresponsive to or ineligible for laser treatment.

Hyperhomocysteinemia and central retinal vein occlusion in Iranian population

PURPOSE

To evaluate total plasma homocysteine level during the acute phase of central retinal vein occlusion (CRVO) in the Iranian population and determine whether hyperhomocysteinemia is also a risk factor for CRVO.

METHODS

Fifty-four patients with recently diagnosed CRVO were studied. Their fasting total plasma homocysteine level was compared with a matched control group of 51 patients evaluated in the same clinic for a non-retinal disease diagnosis.

RESULTS

The mean total plasma homocysteine level was 14.76+/-7.67 micromol/l in cases, and 11.42+/-3.74 micromol/l in control subjects. It showed a significant difference (P=0.005) in mean plasma homocysteine level between cases and control group. Odds ratio of CRVO for individuals with hyperhomocysteinemia was 2.88 (95% CI=1.08-7.71 and P=0.03). The overall multivariable-adjusted odds of CRVO in participants with plasma homocysteine level above 15 micromol/l was 4.71 (95% CI=1.46-15.19 and P=0.009) Hyperhomocysteinemia was not statistically different in each age group (<60 years: 27%, 61-70 years: 33.3%, 71-80 years: 31.6%, >81 years: 33.3%, Chi-square test, P=0.98).

CONCLUSION

Elevated total plasma homocysteine level is an independent risk factor for CRVO in Iranian population. In addition to an evaluation of all conventional cardiovascular risk factors, measurement of total homocysteine for evidence of hyperhomocysteinemia may be important in the initial investigation and management of patients with CRVO.

Investigation of the association between 677C>T and 1298A>C 5,10-methylenetetra- hydrofolate reductase gene polymorphisms and normal-tension glaucoma

PURPOSE

Homozygous polymorphism of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene and resultant hyperhomocysteinaemia have been established as an independent risk factor for vascular diseases. There are evidences that vascular abnormalities are involved in the pathogenesis and progression of normal-tension glaucoma (NTG). In the present study, we were to find out the associations between 677C>T and 1298A>C polymorphisms of the MTHFR gene and NTG.

METHODS

This was a retrospective, case-controlled study enrolling 78 NTG patients and 100 controls. DNA from peripheral blood lymphocytes was extracted and the genotypes of polymorphisms (677C>T and 1298A>C) in the MTHFR gene were determined using PCR followed by restriction enzyme digestion. The frequencies of the polymorphic genotypes in the patients with NTG and controls were compared.

RESULTS

The frequencies of the polymorphisms of the MTHFR gene (677C>T and 1298A>C) in the NTG patients were not significantly different from those of controls. But the younger NTG patients (age at diagnosis < or = 45 years) showed significantly higher prevalence of 677C>T polymorphism than the older NTG patients (age at diagnosis > 45 years) (TT genotype, 38.9 vs 11.9%, P=0.006, OR=4.71, 95% CI=1.49-14.9) and than the younger control subgroup (TT genotype, 38.9 vs 6.1%, P=0.001, OR=9.86, 95% CI=2.23-42.4).

CONCLUSIONS

The 677C>T polymorphism was significantly associated with NTG in the younger patients, while 1298A>C polymorphism was not. This suggests that 677C>T polymorphism of the MTHFR gene can be a genetic risk factor of NTG in Korean population.

Hyperhomocysteinemia and the methylenetetrahydrofolate reductase 677C-T mutation in patients under 50 years of age affected by central retinal vein occlusion

PURPOSE

To investigate the correlation between increased homocysteine plasma levels and the homozygosity for the 677C-T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in patients aged under 50 years affected by central retinal vein occlusion (CRVO).

DESIGN

Prospective, case-control study.

PARTICIPANTS AND CONTROLS

Participants included 31 consecutive patients under 50 years and diagnosed with CRVO. Two controls per case were selected. The first control group (group I) included 31 individuals matched for age, gender, laboratory tests, and the main risk factors for atherosclerosis. The second control group (group II) consisted of 31 volunteers matched only for age and gender.

METHODS

Fasting (>10 hours) blood samples were obtained from patients and controls. Blood samples were obtained from patients within 1 week after the onset of the vaso-occlusive event. Molecular genetic analysis for the 677C-T mutation in the MTHFR gene was performed in patients and controls. A plasma homocysteine reading of >12 micromol/l was considered an increase.

MAIN OUTCOME MEASURES

The total homocysteine plasma level (determined by the high-performance liquid chromatography method with fluorescence detection) and molecular genetic analysis for the 677C-T mutation in the MTHFR gene in patients and controls.

RESULTS

Mean ages were 44.5 years in the group comprising the patients and 44.3 and 44.2 years, respectively, in groups I and II. Mean homocysteine plasma levels were 10.60 micromol/l in patients and 10.39 and 9.34 micromol/l, respectively, in groups I and II. There was no statistically significant difference between mean homocysteine plasma levels in patients and group I controls. In fact, the mean homocysteine plasma level was lower in group II than in patients, and the difference was statistically significant. Homozygosity for the 677C-T mutation in the MTHFR gene was found in 4 patients (12.9%), 5 controls in group I (16.1%), and 4 controls in group II (12.9%).

CONCLUSION

The results of the present investigation support the hypothesis that the homocysteine plasma level is not to be considered a primary and independent risk factor for CRVO, but is more likely a marker of atherosclerosis and the consequence of other well-established risk factors. Moreover, the importance of the study design is brought out, because the results we obtained differ on the basis of the considered control group. This feature may in part explain the contradictory results reported in the literature.

Meta-analysis of plasma homocysteine, serum folate, serum vitamin B12, and thermolabile MTHFR genotype as risk factors for retinal vascular occlusive disease

PURPOSE

To assess the role of plasma total homocysteine (tHcy) levels, serum folate and vitamin B(12)levels, and homozygosity for the thermolabile methylenetetrahydrofolate reductase genotype (TT) as risk factors for retinal vascular occlusive disease.

DESIGN

Meta-analysis of literature.

METHODS

A MEDLINE search was performed to identify all published case-control studies of plasma tHcy levels, serum folate and vitamin B(12) levels, and TT genotype in persons with retinal vascular occlusive disease. Main outcome measures included calculation of plasma tHcy, serum folate, and serum vitamin B(12) standard differences and odds ratios (OR) of TT genotype between cases and controls.

RESULTS

In total, 614 patients with all types of retinal vein occlusion had higher plasma tHcy levels than 762 control subjects (standard difference, 0.867; 95% confidence interval [CI] = 0.735, 0.999; P <.001). Plasma tHcy levels were also higher in 154 patients with retinal artery occlusion compared with 358 control subjects (standard difference 1.174; 95% CI = 0.947, 1.402; P <.001). Serum folates, but not vitamin B(12) levels, were lower in 287 patients with retinal vascular occlusion than in the same number of control subjects (standard difference, 0.508; 95% CI = 0.340, 0.675; P <.001; and -0.060; 95% CI = -0.024, 0.104; P =.474, respectively). Similar proportions of 690 patients with retinal vein occlusion and 2754 control subjects demonstrated the TT genotype (OR = 1.332; 95% CI = 0.995, 1.783; P =.054) as did 152 patients with retinal artery occlusions and 435 control subjects (OR = 1.716; 95% CI = 0.977, 3.014; P =.060).

CONCLUSIONS

Retinal vascular occlusion is associated with elevated plasma tHcy levels and low serum folate levels, but not serum vitamin B(12) levels and TT genotype. Until a prospective multicenter trial is undertaken, plasma tHcy levels and serum folate levels should be determined in patients with retinal vascular occlusions, and dietary supplementation with low doses of folate and vitamin B(12) should be considered for affected persons.

Genetic determinants of fasting and post-methionine hyperhomocysteinemia in patients with retinal vein occlusion

INTRODUCTION

Moderate hyperhomocysteinemia is considered a risk factor for both venous and arterial thrombosis. A prevalence of up to 30% of fasting hyperhomocysteinemia has been recently reported in patients with retinal vein occlusion (RVO) whereas conflicting data exist on the role of C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene as a risk factor for RVO. No report has been published on cystathionine beta-synthase (CBS) 844ins68 polymorphism (another genetic determinant of blood Hcy levels) in RVO patients. Moreover, scarce information is available on the usefulness of measuring homocysteine also after methionine loading to increase the diagnostic efficacy of hyperhomocysteinemia in RVO patients.

MATERIALS AND METHODS

In 55 consecutive patients with diagnosis of RVO and 65 matched controls, plasma fasting total homocysteine (Hcy) levels and CBS and MTHFR polymorphisms were evaluated. In patients with normal fasting Hcy levels, post-methionine Hcy levels were determined.

RESULTS

Moderate fasting hyperhomocysteinemia was detected in 18/55 patients (32.7%). In the remaining 37 patients, Hcy was measured again post-methionine loading (PML). Only 3/37 (8.1%) patients had PML hyperhomocysteinemia. Thus, the total prevalence of moderate hyperhomocysteinemia in this cohort of RVO patients was 21/55 (38.2%). The prevalence of homozygosity for C677T MTHFR genotype, but not that of heterozygosity for CBS844ins68, was significantly higher in RVO patients than in controls.

CONCLUSIONS

Differently from what has been reported for arterial and/or venous thrombosis, a single fasting Hcy measurement is able to detect most of RVO patients (85.7%) with moderate hyperhomocysteinemia. C677T MTHFR, but not CBS 844ins68, genotype may play a role as risk factor for RVO.

Hyperhomocysteinemia and retinal vascular occlusive disease

PURPOSE

Elevated plasma homocysteine is an independent risk factor for thrombosis and vascular disease. This prospective study compared plasma total homocysteine levels in patients with retinal vascular occlusive disease and in matched healthy controls.

METHODS

We measured plasma total homocysteine in 56 consecutive patients with recently diagnosed retinal vascular occlusive disease: 36 had central retinal vein occlusion, 12 branch retinal vein occlusion, and 8 retinal artery occlusion, and compared them with 59 age- and sex-matched healthy controls. Homocysteine levels were determined by high-performance liquid chromatography with electrochemical detection. Hyperhomocysteinemia was defined as a plasma homocysteine level above the 95th percentile in the control group (13.6 micromol/L).

RESULTS

Mean plasma total homocysteine levels were significantly higher in patients than controls (16.1 +/- 8.3 vs. 8.96 +/- 5.6 micromol/L p < 0.001). Mean homocysteine levels were significantly higher in the retinal vein occlusion and retinal artery occlusion groups than the control group (15.3 +/- 8.2 and 20.95 +/- 6.9 vs 8.96 +/- 5.6 micromol/L, p < 0.001). Estimates of the relative risk indicated that the risk of hyperhomocysteinemia was significantly higher in patients with retinal vascular occlusive disease than controls. Hyperhomocysteinemia was present in 37 (66.1%) of the 56 patients with retinal vascular occlusive disease but only 2 (3.4%) controls (odds ratio [OR] 47.5, 95% confidence interval [CI] 9.8-149.9). Hyperhomocysteinemia was present in 29 (60.4%) of the patients with retinal vein occlusion (OR 43.5, 95% CI 8.77-141.93) and in 6 (75%) patients with retinal artery occlusion (OR 85.5, 95% CI 7.49-1,173.1).

CONCLUSIONS

High plasma homocysteine is a risk factor for retinal vascular occlusive disease so it may be useful to measure homocysteine in the management of these patients. A randomized, controlled trial is required to study the effect of lowering with homocysteine folic acid and other B vitamins on the risk of recurrent vascular occlusion in the same eye or its development in the fellow eye.

The role of hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR) C677T mutation in patients with retinal artery occlusion

PURPOSE

Hyperhomocysteinemia has been established as an important risk factor for cardiovascular diseases. The aim of the present study was to investigate whether hyperhomocysteinemia and/or homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation are associated with an increased risk for retinal artery occlusion (RAO).

DESIGN

Retrospective case-control study.

METHODS

We studied 105 consecutive patients with retinal artery occlusion and 105 age and sex-matched control subjects. Fasting plasma homocysteine levels were determined by high-performance liquid chromatography, while genotypes of the MTHFR C677T mutation were determined by polymerase chain reaction.

RESULTS

Mean plasma homocysteine levels were significantly higher in patients with RAO compared with control subjects (12.2 +/- 4.8 micromol/l vs 10.3 +/- 3.4 micromol/l; P =.003). Hyperhomocysteinemia was defined by the 95th percentile of control plasma homocysteine levels as 15.8 micromol/l. Twenty (19.1%) patients with RAO exceeded this level and were therefore classified as hyperhomocysteinemic compared with 5 (4.8%) control subjects (P =.003). The odds ratio for these patients was calculated at 4.7 (95% confidence interval [CI], 1.5-15.1). Mean plasma folate levels were significantly lower in patients than in the control group (5.6 +/- 2.3 ng/ml vs. 6.3 +/- 2.5 ng/ml; P =.04). The prevalence of the homozygous genotype of methylenetetrahydrofolate reductase C677T mutation did not significantly differ between patients and controls.

CONCLUSIONS

Our results suggest that hyperhomocysteinemia, but not homozygosity, for the MTHFR C677T mutation is associated with RAO.

Cardiovascular and thrombophilic risk factors for central retinal vein occlusion

Retinal vein occlusion (RVO) is a relatively common disease that is often associated with a variety of systemic disorders including arterial hypertension, diabetes mellitus, dyslipidemia, and systemic vasculitis. There are various types of RVO, categorized on the basis of the site of occlusion and on the type of consequent vascular damage. Central retinal vein occlusion (CRVO) is the most frequently occurring and clinically relevant type of RVO. In addition to the well-known classical risk factors, new hemostasis-related ones have been investigated in patients affected by CRVO. The data concerning a number of parameters remain contradictory; yet, high levels of type 1 plasminogen activator inhibitor (PAI-1) and hyperhomocysteinemia appear to play a significant role in the pathogenesis of this disease. Although based on a limited number of studies, this new knowledge could eventually provide important indications regarding prognosis and therapeutic strategies.