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Coping with Cancer > Side Effects > Febrile Neutropenia > Overview
Neutropenia
Carolyn Vachani, RN, MSN, AOCN
Abramson Cancer Center of the University of Pennsylvania
Last Modified: September 5, 2006
What are white blood cells?
White blood cells (WBC) are just one piece of the very complex immune system in our bodies. This system is responsible for fighting infection and protecting our bodies from harmful bacteria, viruses and other foreign invaders. There are five different types of white blood cells, each with its own purpose in the immune system: neutrophils (accounting for 50-70% of the WBCs), lymphocytes (25-35%), monocytes (4-6%), basophils (0.4-1%), and eosinophils (1-3%). A WBC count with differential is the blood test that reports the numbers of these cells in the blood.
What are neutrophils and neutropenia?
Neutrophils make up the majority of WBCs and are formed in the bone marrow. They are the “first responders” and quickly appear at the site of infection, ingesting and destroying foreign particles. They can be found in the pus of a wound and play a role in acute inflammation (redness, warmth, swelling, and pain). A normal neutrophil count (also called absolute neutrophil count or ANC) is between 2500 and 5000. A low neutrophil count is known as neutropenia. Neutropenia can be caused by a congenital or inherited disorder, or can be a side effect of a medication or radiation therapy. Chemotherapy medications are the most common cause of neutropenia, but other medications can also cause neutropenia, including (but not limited to): sulfonamides (Bactrim), allopurinol, ibuprofen, indomethasone, several types of antibiotics, blood pressure and anti-seizure medications. For the purposes of this article, we will only discuss neutropenia caused by cancer therapies.
Mature neutrophils are sometimes called “segs”, named for their segmented nucleus. Immature neutrophils are called “bands” because their nucleus appears banded. These 2 counts together make up the absolute neutrophil count, or ANC.
A mature neutrophil
Cancer therapies, including chemotherapy, biotherapy, and radiation therapy, can cause neutropenia. This is because these therapies are unable to tell the difference between cancer cells and healthy cells. Most chemotherapies work by killing rapidly dividing cells. Cancer cells divide rapidly, but so do blood / bone marrow cells, hair follicles, and the cells that line the gastrointestinal tract (mouth, throat, stomach, and bowel). Damage to these normal cells leads to the side effects we see with chemotherapy (low blood counts, hair loss, mouth sores, and diarrhea). Radiation damages blood cells by affecting the marrow production in the bones in the area of treatment.
Why is neutropenia important?
A low neutrophil count greatly increases the risk of developing an infection because your usual mechanism to respond to infection (neutrophils) is not available. There are various levels of neutropenia, but the lower the ANC, the higher the risk of developing infection.