However, increasing studies found that the frequency of TPMT mutation is considerably lower in Chinese than in Caucasians, with the lowest frequencies observed in Chinese (about 0.9%; Fangbin et al., 2012; Zhu and Cao, 2012) compared with a higher incidence of AZA-induced leukopenia (27–41.3%; Connell et al., 1993). This evidence concerns the gene TPMT and Decreased total leukocyte count.