Leukocytosis

Basics

Description

Definition:

  • Any elevation of total number of white blood cells (WBCs) beyond expected value
  • Leukocytosis is one of the most common lab abnormalities (found in 17% of ED patients in whom a CBC is checked)
  • Normal range for total WBCs (/mm3):
    • Adults: 4500–11,000
    • Children: WBC count decreases with age:
      • Infant, 1 wk old: 5000–21,000
      • Toddler, 1 yr old: 6000–17,500
      • Child, 4 yr old: 5500–15,500
    • Pregnancy:
      • 1st trimester: 5000–14,000
      • 2nd trimester: 5000–15,000
      • 3rd trimester: 5000–17,000
  • Normal ranges shift slightly upward with:
    • Exercise
    • Female gender
    • Smoking
    • Daytime hours
  • Given wide range of normal values, numbers must be interpreted in clinical context
  • Specific subsets:
  • Neutrophil predominance (neutrophilia):
    • Absolute neutrophil count >7500/mm3
    • Half of circulating neutrophils are adherent to blood vessel walls. They can be rapidly released (demarginate) in response to acute stressors. This can double the WBC count
    • An additional pool of mature neutrophils, immature metamyelocytes, and band neutrophils are stored in the bone marrow. These can be released, increasing the neutrophil count, typically during inflammation or infection. Release of immature forms results in a “left shift”
  • Lymphocyte predominance (lymphocytosis):
    • Absolute lymphocyte count >4000/mm3
    • Stored in the spleen, lymph nodes, thymus, and bone marrow. They are typically released in response to foreign antigens or viral infections
  • Leukemoid reaction (WBC >50,000/mm3):
    • Increased neutrophils or lymphocytes, occurs in response to disease/stress must be distinguished from hematologic malignancy
  • Hyperleukocytosis (WBC >100,000/mm3):
    • Seen primarily in hematologic malignancies
    • Can be associated with leukostasis, disseminated intravascular coagulopathy (DIC), and tumor lysis syndrome
  • Leukostasis
    • Impaired microvascular blood flow from increased viscosity with high concentration of malignant cells
    • Most commonly effects pulmonary, brain microcirculation
    • Most commonly seen in AML

Etiology

  • Neutrophilia:
    • Demargination/stress reaction:
      • Stress
      • Exercise
      • Surgery
      • Seizures
      • Trauma
      • Hypoxia
      • Pain
      • Panic attacks
      • Vomiting
    • Inflammation:
      • Rheumatoid arthritis
      • Gout
      • Inflammatory bowel disease
      • Vasculitis
    • Infection, generally bacterial:
      • Diarrhea consider C. difficile, shigella
    • Lab error
    • Labor
    • Leukemoid reaction (TB, Hodgkin, sepsis, metastasis)
    • Medications:
      • β-Agonist (epinephrine, cocaine, albuterol)
      • Corticosteroids
      • Lithium
      • Granulocyte colony–stimulating factor
    • Metabolic disorders:
      • DKA
      • Thyrotoxicosis
      • Uremia
    • Malignancy, nonhematogenous
    • Myeloproliferative neoplasm:
      • Myelofibrosis
      • Essential thrombocythemia
      • Polycythemia vera
      • Chronic myelogenous leukemia
    • Pregnancy
    • Rapid RBC turnover:
      • Hemorrhage
      • Hemolysis
    • Smoking
    • Tissue necrosis:
      • Cancer
      • Burns
      • Infarction
  • Lymphocytosis:
    • Infection, generally viral, early stages:
      • Infectious mononucleosis
      • VZV
      • CMV
      • Viral hepatitis
    • Infection bacterial, specifically:
      • Pertussis
      • TB
      • Syphilis
      • Rickettsia
      • Babesia
      • Bartonella
    • Hematologic malignancy/lymphoproliferative disorders:
      • Acute lymphocytic leukemia
      • Chronic lymphocytic leukemia
      • Non-Hodgkin lymphoma
    • Hypothyroidism
    • Immunologic responses:
      • Immunization
      • Autoimmune diseases
      • Graft rejection
    • Splenectomy
  • Monocytosis:
    • Infection:
      • EBV
      • Fungal
      • Protozoa
    • Autoimmune/rheumatologic disorders
    • Splenectomy
  • Eosinophilia:
    • Infection, primarily parasitic and fungal
    • Allergic disorders:
      • Allergic rhinitis
      • Asthma
      • Drug reaction/hypersensitivity
    • Hematologic malignancy
    • Connective tissue disease
  • Basophilia:
    • Allergic disorders
    • Hematologic malignancy

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