White blood cells play a key role in defending the body against invading bacteria and viruses. When white blood cell levels become too low, a condition known as neutropenia, an individual may become more susceptible to infection. A number of diseases are known to lower white blood cell numbers. If you are found to have such a disease, your doctor may monitor your white cell counts to ensure they remain at proper levels.
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The National Heart Lung and Blood Institute explains that aplastic anemia is a disorder of the bone marrow in which the bone marrow fails to produce sufficient red blood cells and white blood cells. Aplastic anemia can be caused by exposure to certain toxins such as pesticides, arsenic and benzene. Radiation can also damage the bone marrow and lead to aplastic anemia. Autoimmune disorders such as rheumatoid arthritis can also lead to bone marrow failure and low white cell counts.
HIV and AIDS
A number of viral infections are associated with lower white blood cell counts. The Johns Hopkins Point of Care Center specifically describes HIV infection as a cause of neutropenia. HIV infection can decrease the growth of progenitor cells involved in white cell production. HIV can also lower levels granulocyte colony stimulating factor (G-CSF), a hormone that regulates white cell production by bone marrow. Drugs used to treat HIV such as AZT may also lower white blood cell levels.
The Mayo Clinic describes leukemia as a cancer of the bone marrow that disrupts the production of blood cells. Leukemia often results in the production of a large number of abnormal white blood cells. While leukemia patients may appear to have large numbers of white blood cells, such cells are typically non-functional and can not perform normal white cell activities.
Lupus is an autoimmune condition in which the body produces antibodies which attack healthy tissues. The effects of lupus often results in inflammation and damage to healthy cells and tissues. Certain types of lupus, specifically systemic lupus erythematosus, can lead to the destruction of white blood cells. As antibodies attack and destroy healthy white blood cells, white cell numbers decline. The Lupus Foundation of America explains that while neutropenia is very common in lupus, white cell levels rarely reach low enough levels to increase susceptibility to severe infection.