Similarly, in 2015, Aráoz and collaborators reported that in a cohort of 286 Argentine children diagnosed with ALL, carriers of the MTHFR rs1801133 A allele (A vs. GG) had a higher risk of leukopenia and neutropenia (p = 0.004 y p = 0.010, respectively) when treated with MTX at a dose of 2 g/m2/day. The gene discussed is MTHFR; the disease is Decreased total leukocyte count.