Multivariable analysis revealed that patients who are homozygous (CC) for XDH rs2281547 were 2.956 times (AHR 2.956, 95% CI = 1.494–5.849, p = 0.002) more likely to develop grade 4 neutropenia than those with the TT genotype. This evidence concerns the gene XDH and Decreased total neutrophil count.