Lymphocytes are special types of white blood cells that form an important part of the body's immune system. The presence of an abnormally high number of lymphocytes in the blood is known medically as lymphocytosis. Although lymphocytosis can exist without the presence of disease, it is more commonly caused by factors such as infection, autoimmune disorders, or certain types of cancer. There is no specific treatment for the condition, as this is more of a symptom than an actual illness. Instead, the treating physician will likely order additional tests to find the root cause of this symptom so that the originating illness can be properly treated.

In the majority of cases, lymphocytosis is diagnosed when a doctor is performing tests due to an illness that is already present. This symptom is rarely found by accident. The combination of various test results along with the diagnosis of lymphocytosis is often enough to help the doctor to know what is causing the illness. It is possible for the lymphocyte count to be slightly elevated without any disease being present, although many doctors will choose to order additional tests to make sure there are no underlying health concerns.

The presence of an infection in the body is a common cause of lymphocytosis. These infections may be caused by a fungus, a virus, or bacteria. Prescription medications are often used to treat the infection, although diagnostic testing may be necessary in order to determine the source of the infection. This is an important step because treatment options for one type of infection will not be useful if another type of infection is causing the illness.

Autoimmune disorders are another potential cause of lymphocytosis. Medical conditions that compromise the immune system often cause inflammation throughout the body. This chronic inflammation may cause an elevation in lymphocytes as the body attempts to identify and battle foreign invaders. Unfortunately, when an autoimmune disorder is present, this process does not work properly, and the body ends up attacking healthy organs and tissues, leading to further inflammation and illness.

Certain forms of cancer may lead to the development of lymphocytosis. This symptom is most common in the types of cancer that affect the blood and the bone marrow. Cancer treatment may or may not help to resolve this elevation of the lymphocytes. Any questions or concerns about blood test results of an elevation in white blood cells should be discussed with a doctor or other medical professional.