A low lymphocyte count can be caused by the body's inability to make lymphocytes, the body's inability to make the necessary amount of lymphocytes or when lymphocytes are trapped in the lymph nodes or spleen. Low lymphocyte counts can also be caused by diseases such as autoimmune disorders, infectious diseases, blood cancer, steroid therapy, chemotherapy treatments and radiation treatments.
Some people who have inherited genetic diseases are more prone to get lymphocytopenia, which is the name for the condition of having a low lymphocyte count. These disease include Wiskott-Aldrich syndrome, DiGeorge anomaly, ataxia-telangiectasia and severe combined immunodeficiency syndrome. Doctors have also found that some people seem to have lymphocytopenia for no reason, and these doctors are unable to find any underlying reasons for the condition.
Lymphocytes are white blood cells that play an important role in the immune system. They keep a person's body from getting infected with viruses, bacteria and other infections. Lymphocytes are made up of NK cells (natural killer cells), T cells and B cells. The lymphocytes make up of 15 to 40 percent of the white blood cell count in a person's body, according to MDhealth. Healthy adults should have a count between 1,000 and 4,800 cells in each microliter of blood for a normal range. Less than 1,000 cells in a microliter would signal lymphocytopenia.