About Leukemoid Reactions in Pediatrics

Background: Leukemoid reaction (white blood cells [WBC] of 30000/mL or more) is rare in children and adolescents. It is commonly associated with infections and may indicate serious conditions. There is a lack of data regarding the underlying causes and the necessary work-up.

Objective: Investigate the clinical and laboratory characteristics of children and adolescents with leukemoid reaction.

Methods: Retrospective study consulting the clinical files of children and adolescents (>1 month to 17 years old) presenting with WBC of 30000/mL or more, in a second level hospital, in 2017. Demographic, clinical and laboratory parameters were analyzed.

Results: A total of 29 patients were included, aged between 3 months and 9.7 years (median 1.6 years), with equal gender distribution. The majority (65.5%) were previously healthy. Fever was present in 79.3% (31% on the first day; 17.2% on the second; 13.8% on the third) and vomiting in 41.1%. The WBC count ranged from 30000 to 56100/mL (mean 34628/mL; neutrophilia was predominant in 93.1%, lymphocytosis in 6.9%) and reactive-C protein ranged from 0.5 to 38.8 mg/dL (mean 10.3 mg/dL). The most common diagnosis were: pneumonia (17.2%), vomiting (17.2%), skin and soft tissue infection (13.8%), urinary tract infection (10.3%) and others (febrile convulsion, acute otitis media, adenoiditis, tonsillitis, mononucleosis-like illness, appendicitis). In seven cases, viral etiology was likely. Sixty-two percent were hospitalized, with a median hospitalization length of three days. Antibiotic therapy was performed in 65.5%. Four of the urine cultures were positive (4/15, mostly Escherichia coli). All the blood (n=18) and cerebrospinal fluid (n=2) cultures were sterile. There were no cases of hemato-oncological disease, glucocorticoid administrations or polyethylene glycol intoxications.

Conclusion: Fever and/or vomiting were present in a significant number of leukemoid reactions. Almost two-thirds were hospitalized and treated with antibiotic. Leukemoid reactions in healthy children can be related to benign and common diseases as we find in our study.