Kantar et al. [3] reported that the MTHFR A1298C polymorphism caused severe hematological toxicity in patients with higher serum MTX levels, specifically anemia (62.5% of 37 cases), thrombocytopenia (51.5%), and aspartate aminotransferase elevation (11.8%). The gene discussed is MTHFR; the disease is anemia (phenotype).