Neonatal Leukemoid Reaction with Fetal Inflammatory Response Syndrome Is Associated with Elevated Serum Granulocyte Colony Stimulating Factor and Interleukin-6

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Leukemoid reaction (LR) is a reactive disease that exhibits abnormal blood values similar to leukemia, but not due to leukemia. One report showed that neonatal LR (NLR) was associated with elevated serum granulocyte colony stimulating factor (G-CSF) in only 30% of the study neonates. NLR is not always associated with the elevation of serum G-CSF. NLR was defined as a white blood cell count of ≥ 40 × 10³/μL and/or blast cell concentration of > 2%. We have focused on NLR with fetal inflammatory response syndrome (FIRS), defined as a fetal systemic inflammatory reaction triggered by intrauterine infection. FIRS was diagnosed based on a cord serum interleukin-6 (IL-6) concentration ≥ 17.5 pg/mL and histopathological chorioamnionitis. Because NLR is highly associated with FIRS, we have hypothesized that NLR is associated with the elevation of both G-CSF and IL-6. This is the first report to measure multiple cytokines in NLR at the same time. The study comprised 19 preterm infants with FIRS: 8 with NLR (study group) and 11 without NLR (control group). Serum G-CSF and IL-6 concentrations were significantly higher in the study group than the control group. There was a positive correlation between G-CSF and IL-6 levels in the study group but not in the control group. These results suggest that elevated serum G-CSF and IL-6 may underlie NLR. Thus, G-CSF and IL-6 concentrations may be predictive of the onset of NLR. Measuring these cytokines is useful for judging the prognosis of preterm infants and for their post-natal clinical management.