Leukemoid reaction in the pediatric population: etiologies, outcome, and implications

Area of Science:

• Pediatric Hematology
• Pediatric Infectious Diseases
• Clinical Pediatrics

Background:

• Leukemoid reaction, defined by a white blood cell (WBC) count > 30,000/μL, often signifies serious underlying conditions, primarily infections.
• Limited population-based data exists regarding the presentation, characteristics, and diagnostic workup of leukemoid reactions in children.
• In adults, leukemoid reactions are linked to increased morbidity and mortality.

Purpose of the Study:

• To investigate the clinical presentation, characteristics, and outcomes of pediatric leukemoid reactions.
• To identify key differences between children with and without leukemoid reactions.
• To assess the association between specific WBC counts and the risk of leukemia in children.

Main Methods:

• Retrospective analysis of a tertiary pediatric medical center database from 2009-2014.
• Inclusion criteria: children with at least one WBC count ≥ 30,000/μL.
• Control group: children admitted with WBC < 30,000/μL. Data collected included demographic, clinical, and laboratory parameters.

Main Results:

• Pneumonia was the most frequent diagnosis in the leukemoid reaction group, with a 5.5-fold higher prevalence of pleuropneumonia compared to controls.
• The leukemoid reaction group experienced longer hospital stays (7.5 vs. 5.5 days).
• Patients with WBC ≥ 50,000/μL had a sixfold higher incidence of leukemia, associated with low platelets, low C-reactive protein, and high uric acid and lactate dehydrogenase levels.

Conclusions:

• Pediatric leukemoid reactions are associated with a high risk of pneumonia, particularly pleuropneumonia, and prolonged hospitalization.
• A WBC count ≥ 50,000/μL significantly increases the risk of leukemia in children.
• Awareness of leukemia-associated variables is crucial for prompt diagnosis in children presenting with leukemoid reactions. No increased mortality was observed in this pediatric cohort.