In 2014, a study from Korea revealed that a single-nucleotide polymorphism in the nucleoside diphosphate-liked moiety X-type motif 15 (NUDT15) gene, in which C at position 415 changes to T, was strongly associated with acute severe leukopenia induced by thiopurines [174]. This evidence concerns the gene NUDT15 and Decreased total leukocyte count.