Non-Infectious Causes of Leukocytosis

Inflammatory and Autoimmune Conditions

• Adult-Onset Still's Disease (AOSD) commonly presents with marked leukocytosis due to neutrophilia, which often accompanies increased disease activity 1, 2
• Chronic inflammatory conditions can cause persistent leukocytosis through ongoing stimulation of bone marrow granulocyte hyperplasia 1
• Patients with AOSD may have white blood cell counts exceeding 15,000 cells/μL in 50% of cases, with 37% having counts >20,000 cells/μL 1

Hematologic Malignancies

• Chronic lymphocytic leukemia (CLL) often presents with progressive lymphocytosis with increases of >50% over a 2-month period or lymphocyte doubling time of <6 months 3, 4
• Acute myeloid leukemia (AML) can present with hyperleukocytosis (WBC >100,000/μL), which constitutes a medical emergency due to risk of hemorrhagic events, tumor lysis syndrome, and leukostasis 5, 6

Management Considerations for Severe Leukocytosis

• Aggressive hydration (2.5-3 liters/m²/day) should be implemented immediately in cases of severe leukocytosis 7
• Hydroxyurea (50-60 mg/kg/day) can be used to rapidly reduce white blood cell counts in hyperleukocytosis 5, 7
• Monitor for and prevent tumor lysis syndrome with allopurinol or rasburicase in high-risk patients 7