ATIC and psoriasis: Genotypic associations and odds ratios (OR) for the carriage of allele 2 [with 95% confidence interval (CI)] for previously investigated single nucleotide polymorphisms in the genes methylenetetrahydrofolate reductase (MTHFR) and 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (ATIC) and their association with the efficacy and toxicity of methotrexate in our psoriasis cohort