What causes a high lymphocyte count?


Quick Answer

A high lymphocyte count, also referred to as lymphocytosis, can be caused by acute lymphocytic leukemia, chronic lymphocytic leukemia, cytomegalovirus (CMV) infection, human immunodeficiency virus (HIV), mononucleosis, multiple myeloma, tuberculosis, vasculitis, whooping cough and other viral infections. In adults, a lymphocyte count significantly higher than 3,000 lymphocytes in a microliter of blood is generally considered to be lymphocytosis, according to the Mayo Clinic.

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Full Answer

The Mayo Clinic explains that it is possible to have a high lymphocyte count and display no symptoms. If test results indicate a high lymphocyte count, a person's doctor may perform additional tests to determine if the lymphocyte count is harmless and temporary or it signals a more serious underlying issue, such as blood cancer or a chronic infection.

According to the Mayo Clinic, lymphocytes are an essential part of the immune system and help to rid the body of disease, so it is not uncommon for a high lymphocyte count to occur after an illness. It is rare that a high lymphocyte count is found randomly as it is normally discovered after a doctor has ordered tests to assess a pre-existing condition. Additional testing may not be required if the high lymphocyte count coincides with test results the doctor has already obtained.

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