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Kenna Koehler


  • Common progenitor cells (stem cells) are located in the bone marrow and give rise to erythrocytes, myeloblasts, megakaryoblasts
  • Normal WBC can vary by age and pregnancy, for the purpose of this section will assume this is for an average, non-pregnant adult
  • Chronic mild neutrophilic leukocytosis (10-20k) is common with tobacco use and obesity, both due to mechanisms related to chronic inflammation
  • Reactive (typically 11k-30k): surgery, exercise, trauma, burns, emotional stress
  • Leukemoid reaction (typically 50k-100k): severe infections (fulminant C difficile), organ rejection
  • If greater than 100k, think leukemia or myeloproliferative disorder


  • Neutrophilia: neutrophil count >7k
    • Bacterial infection, pregnancy, rheumatologic disease, steroids, beta agonists, lithium, colony-stimulating factors, splenectomy or functional asplenia, congenital (hereditary/chronic idiopathic neutrophilia), Down syndrome, leukocyte adhesion deficiency, malignancy, smoking, obesity
  • Lymphocytosis: >40% of WBC count or >4,500k/mm3
    • Infections (pertussis, syphilis, CMV, EBV, hepatitis A/B/C, toxo), hypersensitivity reactions, thyrotoxicosis, Addison's disease, hematologic malignancies, “reactive”
  • Monocytosis: >8% of WBC count or >880/mm3
    • Infections (TB, fungal disease, protozoa, tick-borne), autoimmune disease, malignancy (CMML)
  • Eosinophilia: >500/mm3
    • Hypersensitivity (asthma, urticaria, atopic dermatitis, eosinophilic esophagitis), drug reactions, malignancies, connective tissue disease, idiopathic hypereosinophilic syndrome, infections (helminths, Scarlet fever, Hansen's disease), sarcoidosis, SLE
    • Hypereosinophilia if AEC>1500, typically merits heme evaluation
    • Hypereosinophilic syndrome: AEC>1500 and organ dysfunction from eosinophils
  • Basophilia (>100/mm3)
    • CML, thyroid disease, IBC, chronic dermatitis, infections (varicella)