Leukopenia

Leukopenia: WBC<4-4.5X10^3/mm3
Neutropenia: most common cause of leukopenia, classified based on risk of overwhelming infection as

• mild: 1000-1500 cell/mm3
• moderate: 500-1000 cell/mm3
• severe: <500>

Mild/moderate neutropenia can be tx on outpatient basis if a clear, reversible source is identified and no clinical findings are seen. Severe neutropenia with fever should be admitted with panculture and panimaging.

Mechanisms of leukopenia

1. bone marrow injury: drugs, radiation, toxins, infections (mumps, measles, malaria, influenza, parvo, TB, typhoid, tularemia, HIV, EBV) , infiltrative disease of bone marrow (lymphoma, leukemia, and mets from lung, breast, prostate, stomach CA)

2. maturation defect : folic acid/B12 deficiency, neoplasm (ie acute myeloblastic leukemia)

3. sequestration: hypersplenism

4. destruction: autoimmune (ie Systemic lupus erythematosus)

Lymphopenia

lymphocyte count <2x10^3>

Common causes: HIV, corticosteroids, Hodgekin's lymphoma, multiple myeloma, protein-calorie malnutrition