NUDT15 and Decreased total leukocyte count: Clinical evidence from Indian and Asian cohorts consistently demonstrates that NUDT15 carriers are at significantly higher risk of severe leukopenia, hair loss, and intolerance to standard 6-mercaptopurine doses, often necessitating dose reductions to 10%–30% of the conventional starting dose (Khera et al., 2019; Valerie et al., 2016; Lee et al., 2021).