What is the appropriate management for a 17-year-old female with leukocytosis characterized by an elevated absolute neutrophil count and absolute monocyte count?

Management of Leukocytosis in a 17-Year-Old Female

This 17-year-old female with an absolute neutrophil count of 9,258/mm³ and absolute monocyte count of 927/mm³ requires clinical assessment for infection, constitutional symptoms, and organomegaly before determining if observation versus further workup is appropriate. 1

Initial Clinical Evaluation

The first priority is determining whether this represents a reactive process versus a primary hematologic disorder. Focus your assessment on:

• Infectious symptoms: Recent fever, localizing signs of infection (respiratory, urinary, skin), or recent viral illness 1
• Constitutional symptoms: Unintentional weight loss, significant fatigue, fevers, and night sweats that would suggest malignancy 1
• Physical examination: Assess for massive lymphadenopathy (>10 cm) or splenomegaly (>6 cm below costal margin), which would require further investigation 1

Laboratory Assessment

Order a complete blood count with manual differential to assess for band forms and immature cells. 2, 1

Key parameters to evaluate:

• Band count: An elevated absolute band count >1,500/mm³ has the highest likelihood ratio (14.5) for bacterial infection 2
• Left shift: >16% bands or neutrophil percentage >90% suggests bacterial infection 2, 1
• Peripheral smear review: Look for toxic granulation, vacuolation, Döhle bodies, or immature myeloid precursors 3

Risk Stratification and Management

Since the white blood cell count is <30,000/µL, observation is appropriate if constitutional symptoms are absent. 1

If No Constitutional Symptoms or Organomegaly:

• Observation with repeat CBC in 2-4 weeks is reasonable 1
• Monitor for lymphocyte doubling time <6 months or >50% increase over 2 months, which would suggest progressive disease 1
• No treatment is indicated for asymptomatic findings alone 1

If Constitutional Symptoms Present:

• Further investigation is mandatory including peripheral smear review, consideration of bone marrow evaluation, and assessment for hematologic malignancy 1
• Consider evaluation for chronic myelomonocytic leukemia if monocytosis persists, though this is rare in this age group 2

If Signs of Infection:

• Bacterial infection is likely if band count >1,500/mm³ or left shift >16% 2
• Initiate appropriate diagnostic workup for source of infection 2
• Consider that bacterial infections can occur with leukocytosis even without fever, particularly in certain populations 2

Common Pitfalls to Avoid

• Do not assume infection without fever: Bacterial infections can present with leukocytosis but normal temperature 2, 1
• Do not ignore relative changes: Even if absolute counts remain in normal range, rapid increases warrant attention 1
• Do not treat asymptomatic findings: Elevated WBC alone without progressive marrow failure, organomegaly, or constitutional symptoms does not require treatment 1
• Do not overlook the clinical context: In a young, otherwise healthy patient, reactive causes (infection, inflammation, stress) are far more common than primary hematologic disorders 1

Follow-Up Strategy

If initial assessment suggests a reactive process:

• Repeat CBC with differential in 2-4 weeks 1
• Reassess for development of constitutional symptoms or organomegaly 1
• If counts normalize or trend downward, continue observation 1
• If counts persist elevated or increase, proceed with peripheral smear review and consider hematology referral 1