Children with leukopenia carriers of the variant allele A for MPO gene polymorphism also had significantly decreased WBC (p = 0.0001), neutrophils (p = 0.0001), eosinophils (p = 0.032), basophils (p = 0.002), monocytes (p = 0.0007), lymphocytes (p = 0.0001), and platelets (p = 0.004); in addition, we also found an elevated free iron level (p = 0.018) (Table 3). The gene discussed is MPO; the disease is Decreased total leukocyte count.