The association between MTHFR gene polymorphism and psoriasis vulgaris was reported by Wang et al. (2000)  and was refuted by the studies conducted in Austria (Weger et al., 2008)  and the Czech Republic (Vasku et al., 2009) . These contradictory findings were postulated to the probable differences in ethnicities. Till date, no other report on the prevalence of this MTHFR gene polymorphism and psoriasis vulgaris was documented for the Asian population. The association of the MTHFR gene polymorphism and psoriasis vulgaris has been postulated due to the higher risk of psoriasis patients developing cardiovascular and cerebrovascular complications. Nonetheless, the pathogenesis is not known till date [5–7, 17, 18].
The association of the MTHFR gene polymorphism and psoriasis vulgaris in the Malaysian population i.e. Chinese, Indian and Malay ethnic groups was investigated in this case-control hospital based study. Two hundred patients and 167 controls were recruited. The methodology of this study was conducted according to Wang et al. (2000) . Our results demonstrated that there was no statistically significant association between MTHFR C > T gene polymorphism and psoriasis vulgaris in the Malaysian population, which consistent with the Austrian  and the Czech Republic's  findings on Caucasian population. Our study thus contradicts the published study in China . Our study also investigated the association of the MTHFR gene polymorphism and ethnicities in Malaysia namely the Chinese, Indian and Malay. We reported that there were no significant association between MTHFR gene polymorphism in psoriasis vulgaris and ethnicities in the Malaysian population. Though a larger sample size of patients was investigated in the present study, we did not find any significant association of the MTHFR gene polymorphism and psoriasis vulgaris as compared with the previous Chinese study on only 39 Chinese patients .
The prevalence of the MTHFR 677 C > T is variable depending on the geography and ethnicity . Botto et al. (2000) reported that the worldwide T allele frequency was highest in the Italian and the Hispanics, and lowest in the American Blacks and sub-saharan Africa. In the European population, the distribution of the homozygous T allele was highest in the Italian and lowest in the German [20–22]. In the Blacks, the frequency of T homozygosity in the sub-Saharan African population showed zero percentage [23, 24]. In Asian, limited data could be retrieved as only the Japanese population was studied and the population percentage of the homozygous T mutation was 11% [25, 26]. An interesting finding that we discovered in this study was the homozygosity of the T genotypes was found only in 2 of the controls but not in the cases. This finding contradicted the Chinese study  which reported the significant increased of homozygous TT in the cases compared with controls (p < 0.05). We hypothesized this variation may be due to the geographical differences as seen in the Europeans .
The MTHFR gene polymorphism was reported to be associated with hyperhomocysteinaemia which has deleterious effects on the cardiovascular system [13, 28]. Hence, psoriasis vulgaris patients with MTHFR gene polymorphism may be at greater risk of cardiovascular diseases and thromboembolic events. Therefore, we investigated the relationship between MTHFR gene polymorphism and homocysteine, vitamin B12 and folic acid levels in selected 41 cases and 43 controls. We demonstrated that there was no significant relationship between the MTHFR gene polymorphism and homocysteine, vitamin B12 or folic acid levels in this subset of subjects.
The relationship of homocysteine, vitamin B12 and folic acid levels compared with the ethnicities and the MTHFR gene polymorphism was analyzed using 3-way ANOVA. We did not find any statistically significant relationship amongst these groups. Nonetheless, males irregardless of the polymorphism of the MTHFR gene have a higher homocysteine levels when compared to the females (p = 0.001). Overall, the Indian males and Malay males have higher homocysteine levels than the Chinese males and a significantly lower folic acid level compared to the Chinese (p = 0.000).
In Malaysia, the dietary intakes varied amongst the ethnic groups and also varied amongst the genders [29, 30]. The Indian and the Malay groups have a higher intake of coconut oil, processed sugars and condensed milk in their diet when compared to the Chinese. We proposed that the significant increased in homocysteine level in the Indian and Malay males might be due to the different dietary intakes between different ethnic groups amongst the males. The observation that the folic acid level that is significantly higher in the Chinese again pinpointed the beneficial effect of folic acid in the lowering of the plasma homocysteine level . Therefore, these differences might be a beneficial consideration to be taken note of when other epidemiological studies are being carried out in these populations in the future.
The limitation of this study was the centrality of the recruitment of the subjects in the area of Kuala Lumpur and Seremban and we did not recruit subjects from the northern, eastern or southern states of Malaysia. Perhaps, there would have been a difference in the genotypes distribution in these places compared with the ones we have recruited. Future studies might be warranted to investigate the variation of the MTHFR 677 C > T gene geographically, perhaps on other Asian populations using a bigger sample size and a larger population. The inclusion of other single nucleotide polymorphism of the MTHFR gene would be beneficial to investigate the association of the presence of synergistic effects of the haplotypes and psoriasis vulgaris.
This study has again pinpointed the independent hyperhomocysteinaemia irrespective of the possession of psoriasis vulgaris, mutation of the MTHFR gene and its prevalence in the male gender. With the prior knowledge of hyperhomocysteinaemia as a risk for cardiovascular and thromboembolic events, routine homocysteine and folic acid screening should be included as part of psoriasis vulgaris and cardiovascular disease management. The routine supplementation of folic acid in the diet of the psoriasis vulgaris patients could be of benefit to them.