What is lymphocytosis?

Lymphocytosis is a higher-than-normal amount of lymphocytes, a subtype of white blood cells, in the body. Lymphocytes are part of your immune system and work to fight off infections.

Who is most at risk for getting lymphocytosis?

Anyone can have lymphocytosis.

How common is lymphocytosis?

Lymphocytosis is very common. It’s especially common in people who have:

What causes lymphocytosis?

Lymphocytosis results from increased numbers of lymphocytes in your blood. Lymphocytes are a type of white blood cell. They play an important role in your immune system, helping your body fight off infection. Many underlying medical conditions can cause lymphocytosis.

High lymphocyte blood levels indicate your body is dealing with an infection or other inflammatory condition. Most often, a temporarily high lymphocyte count is a normal effect of your body’s immune system working. Sometimes, lymphocyte levels are elevated because of a serious condition, like leukemia.

Your doctor can order specific diagnostic tests to help pinpoint the cause of your lymphocytosis. These tests may include other laboratory tests to rule out infections or tests examining other body tissues, like bone marrow biopsy and looking at your blood under a microscope.

What are the symptoms of lymphocytosis?

Lymphocytosis itself does not cause symptoms. However, you may experience symptoms from the underlying cause of lymphocytosis. Depending on the cause, symptoms may range from no symptoms to severe.

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