A larger than normal number of white blood cells, leukocytes, in the blood, called leukocytosis, can occur for many reasons. Bone marrow produces around 100 billion white blood cells each day, with the white blood cell count falling between 4,000 and 11,000 cells per microliter, the Merck Manual states. Bone marrow produces five different types of white blood cells; an elevation of any one can cause leukocytosis.
Types of Leukocytes
Neurophils, basophils, eosinophils, lymphocytes and monocytes make up the white blood cells, with all of these except for monocytes associated together in a category known as granulocytes--of which neutrophils comprise 50 to 75 percent and are the first cell to fight infection. Thus an elevated level of neutrophils most often causes leukocytosis, Dr. Neil Abramson reported in the November 1, 2000 "American Family Physician."
Why White Cell Count Can Increase
Leukocytosis most often occurs as a normal immune response to infection. An increase in immature neutrophils, called bands, usually represents a response to bacterial infection. Neutrophils also rise in response to stress. Lymphocytes, divided into T- and B-lymphocytes, rise in many infections and also increase in lymphatic leukemia.
Causes of leukocytosis include bone marrow abnormalities, cancer, acute or chronic leukemia, acute blood loss, toxins, certain drugs and trauma, according to the University of Kansas Medical Center. Eosinophils rise in asthma, aspirin sensitivity, allergies and drug reaction, plus a number of infections. Basophils and monocytes also rise in response to specific infections and diseases.
Symptoms
Symptoms of leukocytosis depend on the cause. Leukemia can cause pallor, weakness, increased risk of infection, fever and excessive bruising and bleeding. Leukocytosis from an elevated number of eosinophils, which rise in allergic and immunologic reactions, can cause rashes and respiratory problems. Infection causes different symptoms depending on the location. Lymph nodes may be swollen and tender to the touch. The spleen and liver may enlarge.
Anemia--a low red blood cell count--and thrombocytopenia--a low platelet count--may occur if a bone marrow abnormality is present.
Treatment
Addressing leukocytosis begins with determining the exact cause and then planning treatment based on the problem. Infections require antibiotics, while malignancies require chemotherapy or other cancer treatments.
Emergencies
While leukocytosis most often occurs as a normal and helpful response to infection, severe leukocytosis needs medical attention. Leukocytosis greater than 30,000 indicates a bone marrow abnormality and requires immediate medical attention. Levels higher than 100,000--a medical emergency requiring an immediate hematology consult--can cause brain infarction, lack of blood to the brain or hemorrhage, Abramson warns.
