Extreme Hyperleukocytosis in an Extremely Preterm Infant

  • Lucio Ortega TTUHSC
  • Saleena Ramzanali
  • Perla Mora
  • Samer-Zaid Kaylani
  • Olubukunola Adesanya
Keywords: leukocytosis, premature, chorioamnionitis, funisitis, leukemoid reaction.


An extremely preterm male infant at 25.1 weeks gestation developed extreme hyperleukocytosis on Day of life (DOL) 3, with a peak white blood cell (WBC) count of 146.5 ×109/L on DOL 5. The patient was admitted to the NICU due to prematurity, respiratory distress, and suspected sepsis. Laboratory analyses were done to exclude sepsis with a leukemoid-like reaction, Down syndrome by karyotype, leukemia, or other myeloproliferative disorders. After a meticulous investigation and ruling out the most common causes of leukocytosis in preterm neonates, we concluded that the hyperleukocytosis in this extreme premature infant was likely caused by maternal chorioamnionitis and fetal funisitis as reported by placental pathology.

We present this rare case of hyperleukocytosis in an extremely premature infant to highlight the importance of a thorough investigation, including sources of infection in the mother's history and placental pathology report, to determine the cause of hyperleukocytosis in the preterm neonates.


1. Marcdante, Karen J., and Robert Kliegman. Nelson Essentials of Pediatrics. Eighth edition. Philadelphia, PA: Elsevier, 2019. p. 565,600.
2. Parvez, Yusuf, and Aji George Mathew. "Hyperleukocytosis in newborn: a diagnosis of concern." Indian Journal of Hematology and Blood Transfusion 30.1 (2014): 131-132.
3. Jansen E, Emmen J, Mohns T, et al Extreme hyperleucocytosis of the premature Case Reports 2013;2013:bcr2012008385.
4. Jain, Richa, Deepak Bansal, and R. K. Marwaha. "Hyperleukocytosis: emergency management." The Indian Journal of Pediatrics 80.2 (2013): 144-148.
5. Morag, I., et al. "Leukocytosis in very low birth weight neonates: associated clinical factors and neonatal outcomes." Journal of perinatology 28.10 (2008): 680-684.
6. Zipursky, Alvin. "Transient leukaemia–a benign form of leukaemia in newborn infants with trisomy 21." British journal of haematology 120.6 (2003): 930-938.
7. Johann Hitzler, MD, FRCP(C), FAAP Moira Garraus, MD: Transient myeloproliferative disorder of Down syndrome. In: Julie R Park, MD, ed. UpToDate, 2022. Available from: https://www.uptodate.com/contents/transient-myeloproliferative-disorder-of-down-syndrome
8. Shrivastava, Jyoti Priyadarshini, et al. "Congenital acute myeloid leukemia: A rare diagnostic enigma case report with review of literature." South Asian Journal of Cancer 5.04 (2016): 212-213.
9. Avabratha, K. Shreedhara, et al. Hyperleukocytosis in a neonate: A diagnostic dilemma. Indian Journal of Medical and Paediatric Oncology, 2010, vol. 31, no 03, p. 86-88.
10. Barak M, Cohen A, Herschkowitz S. Total leukocyte and neutrophil count changes associated with antenatal betamethasone administration in premature infants. Acta Paediatr. 1992 Oct;81(10):760-3. doi: 10.1111/j.1651-2227.1992.tb12098.x. PMID: 1421878.
11. Rice L, Jung M. Neutrophilic leukocytosis, neutropenia, monocytosis, and monocytopenia. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 48.
12. Kim, Chong Jai et al. Acute chorioamnionitis and funisitis: definition, pathologic features, and clinical significance. American journal of obstetrics and gynecology vol. 213,4 Suppl (2015): S29-52. doi:10.1016/j.ajog.2015.08.040.
How to Cite
Ortega, L., Ramzanali, S., Mora, P., Kaylani, S.-Z., & Adesanya, O. (2022). Extreme Hyperleukocytosis in an Extremely Preterm Infant. Journal of Rare Diseases and Orphan Drugs, 3, 6 - 10. https://doi.org/10.36013/jrdod.v3i.94