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Lymphocytopenia is a condition marked by an abnormally low level of lymphocytes in the blood. Lymphocytes are a specific type of white blood cell with important functions in the immune system.


Lymphocytes normally account for 15-40% of all white cells in the bloodstream. They help to protect the body from infections caused by viruses or fungi. They also coordinate the activities of other cells in the immune system. In addition, lymphocytes fight cancer and develop into antibody-producing cells that neutralize the effect of foreign substances in the blood.

Lymphocytopenia is the result of abnormalities in the way lymphocytes are produced, make their way through the bloodstream, or are lost or destroyed. These conditions can result from congenital or drug-induced decreases in the body's ability to recognize and attack invaders.

Causes and symptoms

Lymphocytopenia has a wide range of possible causes:

  • AIDS and other viral, bacterial, and fungal infections
  • Chronic failure of the right ventricle of the heart. This chamber of the heart pumps blood to the lungs.
  • Hodgkin's disease and cancers of the lymphatic system
  • A leak or rupture in the thoracic duct. The thoracic duct removes lymphatic fluid from the legs and abdomen.
  • Leukemia
  • Side effects of prescription medications
  • Malnutrition. Diets that are low in protein and overall calorie intake may cause lymphocytopenia.
  • Radiation therapy
  • High stress levels
  • Trauma.

The symptoms of lymphocytopenia vary. Lymphocytes constitute only a fraction of the body's white blood cells, and a decline in their number may not produce any symptoms. A patient who has lymphocytopenia may have symptoms of the condition responsible for the depressed level of lymphocytes.


Lymphocytopenia is most often detected when blood tests are performed to diagnose other diseases.


Treatment for lymphocytopenia is designed to identify and correct the underlying cause of the condition.

Drug-depressed lymphocyte levels usually return to normal a few days after the patient stops taking the medication.


B lymphocyte A type of lymphocyte that circulates in the blood and lymph and produces antibodies when it encounters specific antigens. B lymphocytes are also called B cells.

Lymph A clear yellowish fluid circulated by the lymphatic system. The lymph carries mostly lymphocytes and fats.

Lymphocyte A specific type of white blood cell that is important in the production of antibodies.

A deficiency of B lymphocytes, which mature into antibody-producing plasma cells, can result in abnormally low lymphocyte levels. When the number of B lymphocytes is low, the patient may be treated with antibiotics, antifungal medications, antiviral agents, or a substance containing a high concentration of antibodies (gamma globulin) to prevent infection.

It is not usually possible to restore normal lymphocyte levels in AIDS patients. Drugs like AZT (azidothymidine, sold under the trade name Retrovir) can increase the number of helper T cells, which help other cells wipe out disease organisms.


Very low levels of lymphocytes make patients vulnerable to life-threatening infection. Researchers are studying the effectiveness of transplanting bone marrow and other cells to restore normal lymphocyte levels. Gene therapy, which uses the body's own resources or artificial substances to counter diseases or disorders, is also being evaluated as a treatment for lymphocytopenia.



Berktow, Robert, et al., editors. Merck Manual of Medical Information: Home Edition. Whitehouse Station, NJ: Merck Research Laboratories, 1997.

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lymphocytopenia (lim-foh-sy-toh-pee-niă) n. see lymphopenia.

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