It is worth mentioning that Lopez-Lopez 2013 (Lopez-Lopez et al., 2013) reported no association between MTHFR 677C>T and MTX toxicity in pediatric ALL (recessive model), and Oosterom 2018 (Oosterom et al., 2018) reported no association between TYMS 2R>3R and MTX toxicity in pediatric ALL (dominant model), which were contrary to our findings. Here, MTHFR is linked to acute lymphoblastic leukemia.