TPMT and Decreased total leukocyte count: Paradoxically, thiopurine-induced leukopenia is more common in East Asian individuals, and many patients who develop leukopenia after receiving AZA treatment cannot be reliably identified by genotyping or TPMT activity measurements because these patients have normal or near normal TPMT activity (Connell et al., 1993; Takatsu et al., 2009; Kim et al., 2010; Fangbin et al., 2012).