Broekman MMTJ, et al. - An analysis was performed to identify the clinical risk factors for thiopurine-induced leucopenia in patients without a common thiopurine S-methyltransferase (TPMT) variant, and investigate if these patients were at increased risk for infections. In patients without a TPMT variant, low baseline white blood cell (WBC) count and mercaptopurine were risk factors for thiopurine-induced leucopenia because of a relatively higher dose.