Lymphopenia, also known as lymphocytopenia, occurs when there are not enough lymphocytes in the blood. This condition can be a result of several blood disorders or other diseases including Hodgkin’s disease and leukemia. Immune system disorders can also lead to the shortage of lymphocytes.

Lymphocytes are one of the types of white blood cells that are used by the immune system. There are three types of lymphocyte cells. Lymphopenia does not always cause a decrease in all three types, and often there is usually a shortage in just one.

A decrease in T lymphocyte cells, called T lymphocytopenia, can be a cause for many problems. When the cell count falls below 20% of the total count of lymphocytes and there are no immunodeficiency disorders, a diagnosis of this form of lymphopenia is reached. Low T lymphocyte cell counts leave people prone to developing pneumonia, cryptococcus, and other opportunistic infections.

B lymphocytopenia occurs when B lymphocyte cell counts are low, but the other cell counts are normal. With this type of lymphopenia, the immune system cannot properly fight off antigens because B lymphocytes are responsible for antibody production. This variation is often caused by medications that suppress the immune system.

A rare form of lymphopenia is natural killer (NK) lymphocytopenia. It occurs when natural killer cells are low, and the other lymphocyte levels are normal. Natural killer cells are part of the immune system’s defenses. They have the responsibility of destroying damaged and infected cells. With a natural killer deficiency, the absence or low amount of these cells allows the body to be invaded by infections, viruses, and cancers.

Hematopathology is an area of pathology that focuses specifically on red and white blood cells. Through this area of study, scientists were able to determine that lymphopenia is a separate condition from pancytopenia, and that it is limited to the lymphocytes. Blood testing shows that while pancytopenia is a decrease in red cells, platelets, and white blood cells, lymphopenia only involves a decrease in the white blood cells. In some cases, however, the lack of white blood cells can be a part of pancytopenia, depending on what the cause is.

Treatment for lymphopenia varies. If the instance is mild and has no other condition as a cause, treating the decrease is not necessary. Conditions such as Human Immunodeficiency Virus (HIV) and infections should be treated in order to increase lymphocyte cell counts. In an instance where lymphocyte counts decrease due to chemotherapy or other types of treatments, lymphocyte counts generally increase without intervention as the treatment time progresses or when treatment stops.