TPMT and Decreased total leukocyte count: In a recent study [1], we demonstrated that TPMT preemptive genotyping significantly reduced the incidence of leukopenia and other adverse drug reactions (ADRs) in TPMT intermediate metabolizers (IMs) to the level of normal metabolizers (NMs), in the patients preemptively genotyped at our center (Hospital Universitario de La Princesa, Madrid, Spain) receiving azathioprine.