TPMT and Decreased total leukocyte count: However, when intolerant patients were compared to those responding to treatment based on the type of adverse event (Table 1), it was found that 29% (2/7) of patients with at least one haplotype of the TPMT gene experienced leukopenia, in contrast to 3% (8/244) of wild-type patients (OR = 11.8, 95%CI = 1.98–70.36, p = 0.027).