Congenital leukemia presenting as fever in a neonate.

BACKGROUND Emergency department workup of pediatric fever typically focuses on ruling out serious bacterial infection, but other disease processes can cause fever. Congenital leukemia is a rare but important cause of fever in neonates. We review the presentation, pathophysiology, and potential complications of congenital leukemia presenting to the emergency department as pediatric fever. CASE REPORT We report a case of a 4-week-old infant brought to the emergency department for fever and "not acting normally." Complete blood count demonstrated hyperleukocytosis. Subsequent bone marrow biopsy and flow cytometry confirmed the diagnosis of congenital leukemia. The extreme elevation of the patient's white blood cell count put her at high risk for complications, necessitating aggressive treatment, close monitoring, and appropriate consultation for comprehensive care. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS Congenital leukemia is a rare but serious cause of neonatal fever. While the workup for fever without a source in young pediatric patients primarily focuses on ruling out serious bacterial illness, emergency physicians must be familiar with other potentially life-threatening causes of this complaint.