Leukocytosis and Leukopenia
Classification, Etiology, Pathogenesis, and Clinical Manifestations
Definition
Leukocytosis: Increase in total white blood cell (WBC) count above normal (usually >11,000/ μL).
Leukopenia: Decrease in WBC count below normal (usually <4,000/ μL).
Normal WBC range = 4,000 – 11,000 cells/ μL.
Classification
By WBC type affected:
Etiology
Leukocytosis
Leukopenia
Pathogenesis
Leukocytosis
- Increased production in bone marrow (e.g., infections, leukemia ).
- Demargination (neutrophils leave vessel wall into circulation) due to
corticosteroids or stress.
- Delayed apoptosis of WBCs.
Leukopenia
- Decreased production: damage to bone marrow (drugs, aplasia).
- Increased destruction: autoimmune diseases, hypersplenism.
- Redistribution: sequestration in spleen or lymph nodes.
Clinical Manifestations
Leukocytosis (depends on WBC subtype):
- Often asymptomatic.
- If severe: may cause hyperviscosity symptoms (esp. in leukemia ).
- May indicate underlying infection or malignancy.
- Neutrophilia: bacterial infection signs (fever, pus).
- Lymphocytosis: viral infection (EBV – sore throat, fatigue).
- Eosinophilia: allergy, parasitic infection, rash.
Leukopenia:
- Increased risk of infections, especially bacterial and fungal.
- Common signs:
- Fever (may be the only symptom).
- Mouth ulcers.
- Recurrent infections (skin, respiratory, urinary).
- Agranulocytosis: Severe neutropenia → life-threatening infections.