Initial Approach to an 18-Month-Old with Isolated Chronically Elevated Monocytes and Fever

Risk Stratification

The American Academy of Pediatrics recommends that children with fever and elevated monocytes should be risk-stratified to guide management decisions 2
Low-risk features in pediatric patients include an absolute monocyte count >100 cells/mm³, no comorbidity, and normal chest radiograph findings, which identifies children at lowest risk for significant bacterial infections 3
Additional low-risk features include normal vital signs, no dehydration, and normal hepatic and renal function tests 4

The Infectious Diseases Society of America recommends obtaining blood cultures from all lumens of central venous catheters if present, and considering peripheral blood cultures concurrent with central venous catheter cultures 5
Consider urinalysis and urine culture if a clean-catch specimen is readily available, and obtain chest radiography only if respiratory symptoms are present 6
First-tier laboratory testing should include complete blood count with manual differential, complete metabolic panel, and inflammatory markers (C-reactive protein and erythrocyte sedimentation rate) 1

Bacterial infections can cause elevated monocytes with fever, and the presence of certain risk factors can help guide the diagnosis 2
Multisystem inflammatory syndrome in children (MIS-C) should be considered if there's a history of COVID-19 exposure 7

For clinically stable children with isolated monocytosis and fever, close observation without immediate antibiotic therapy is appropriate, and consider outpatient management if the child appears well and meets low-risk criteria 5
For children with signs of clinical instability, initiate empiric antibiotic therapy with an antipseudomonal β-lactam or carbapenem, and reserve addition of a second Gram-negative agent or glycopeptide for patients who are clinically unstable or when resistant infection is suspected 6
Consider discontinuation of empiric antibiotics at 48-72 hours in low-risk patients who have negative blood cultures and have been afebrile for at least 24 hours 2

Avoid premature closure on a diagnosis of "viral syndrome" without appropriate evaluation in a child with persistent fever, and remember that monocytosis can be a nonspecific finding 1
Avoid unnecessary antibiotic use in well-appearing children with fever who meet low-risk criteria 5