These findings were not supported by previous studies.20,21 A study conducted in Slovenia suggested that SLC19A1 rs2838958 AA genotype results in a significant level of mucositis; however, no association with leukopenia was reported.22 Furthermore, our results indicated that SNPs of SLC19A1 have no effect on MTX toxicity. The gene discussed is SLC19A1; the disease is mucositis.