HIGH WHITE CELLS COUNT

High white counts always make me think of leukemia (maybe I just always think of the worst possible scenario). But there are a ton of benign things that can make one's white count go up. Fortunately, these benign conditions are much more common than leukemia.

Neutrophils: bacterial infection, inflammation, metabolic disease (e.g., diabetes), stress (even the anxiety of being in the ER can make your neutrophils demarginate; the neutrophil count can double in this setting!)

Lymphocytes: Viral infection (e.g. infectious mononucleosis, hepatitis), immune disease, stress (lymphocytes don't marginate along the inside of blood vessels - so the count doesn't go up as dramatically as the neutrophil count can)

Eosinophils: skin diseases, drug reaction, parasite infection, asthma

Basophils: chronic myeloid leukemia. Okay, this is not a benign thing. But if you see a basophilia, this is the first thing that should come to mind. There are very few, if any, other causes of basophilia.

Monocytes: infection, solid tumors (rarely, the monocyte count goes up when a patient has a solid tumor somewhere), autoimmune disease

NEUTROPENIA

There are two main categories that inhibit the production of neutrophils, and things that remove neutrophils from the circulation.

Things that inhibit the production of neutrophils:

• Hematopoietic stem cell suppression (e.g., aplastic anemia, infiltrative bone marrow diseases). Note: in these settings, you'd see anemia and thrombocytopenia too (good diagnostic clues).
• Drug reaction (This is the most common cause of neutropenia! The list of drugs is looooong; check out Robbins page 582.)
• Ineffective hematopoiesis (like that seen in megaloblastic anemia and myelodysplasia). 
• Congenital disorders (rare, rare, rare) like Kostmann syndrome, in which patients have defects in genes involved in granulocyte differentiation.

                             

Things that remove neutrophils from the circulation:

• Immunologic processes (like lupus, or drug exposure).
• Splenomegaly (a big spleen sequesters neutrophils - as well as red cells and platelets).
• Overwhelming infection (the patient is using up all the neutrophils by calling them out of the blood into the tissues).

For more on causes of neutropenia, see Robbins Pathologic Basis of Disease ("big Robbins") 9th edition, page 582 (or 8e, page 593).