Acquired causes of a low lymphocyte count include steroid therapy; autoimmune disorders; radiation therapy; chemotherapy; blood diseases such as blood cancer; and infectious diseases such as tuberculosis, explains the National Heart, Lung, and Blood Institute. Inherited causes of a low lymphocyte count include DiGeorge anomaly and Wiskott-Aldrich syndrome.
A low lymphocyte count occurs when the body makes a small number of lymphocytes or when the body makes enough lymphocytes but they are destroyed, according to the National Heart, Lung, and Blood Institute. Some patients have low lymphocyte levels because lymphocytes get stuck in the lymph nodes or spleen. There are patients who suffer from low lymphocyte levels without any explainable cause.
One of the most common acquired causes of low lymphocyte counts is acquired immunodeficiency syndrome, reports the National Heart, Lung, and Blood Institute. This is because human immunodeficiency virus infections destroy CD4+ T cells, explains MSD Manual. Protein energy malnutrition is another common cause of lymphocytopenia.
A low lymphocyte count may be a result of underproduction of lymphocytes due to the destruction of lymphoid or thymic architecture, states the MSD Manual. The lymphocytes may also migrate to the respiratory tract. Some long-term psoriasis treatments may destroy T cells and cause a low lymphocyte count. Lymphocyte levels may reduce briefly when a person is starving, stressed or using corticosteroids.