Transient leukemoid reaction in an extremely premature neonate.

A female newborn was delivered prematurely at gestational age of 26 weeks with birth weight of 1,000 grams. Her initial white blood cell count was 68,900/mm3, which increased to 207,000/mm3 on the fifth day of life with a remarkable shift-to-left pattern. The most immature myeloid series in the peripheral blood smear was promyelocyte; and the promyelocyte, myelocyte and meta-myelocyte accounted for 38% of the peripheral white blood cells. Neither hepatosplenomegaly nor skin rash was noted, but the platelet count dropped to 86,000/mm3 transiently on Day 8. Cytogenetic study for the bone marrow aspiration revealed normal results. The leukemoid reaction recovered within three weeks without specific treatment. Antenatal usage of steroid to promote lung maturation was considered to be one possible cause of the transient leukemoid reaction.