There were no alterations of the expression of Glutathione S-transferases-K1, Glutathione S-transferases-K1, Glutathione S-transferases-T1, cytochrome p450-1B1, and cytochrome p450-2E1 pre–post methotrexate treatment, however their expression was elevated post-methotrexate administration in the psoriasis versus control group. This evidence concerns the gene CYP2E1 and psoriasis.