UGT1A1 ∗28/ ∗28 genotype was associated with more than fourfold (OR, 4.79; 95% CI, 3.28–7.01; p < 0.00001) and threefold (OR, 3.44; 95% CI, 2.45–4.82; p < 0.00001) increases in the risk of neutropenia when compared with wild type and with at least one UGT1A1 ∗1 allele, respectively. This evidence concerns the gene UGT1A1 and Decreased total neutrophil count.