Lymphocytosis

What is lymphocytosis (high lymphocyte count)?

Lymphocytosis — or high lymphocyte count — means having a higher-than-normal amount of lymphocytes in your blood. Lymphocytes are a type of white blood cell. They play an essential role in your immune system, helping your body fight infections.

Having a temporarily high lymphocyte count usually means that your body is working as it should to protect you from germs that make you sick. Less often, lymphocytosis is a sign of a more serious condition.

For adults, a high lymphocyte count means more than 4,000 lymphocytes in 1 microliter of blood.

How common is lymphocytosis?

Lymphocytosis is very common, especially in people who have:

• Had a recent infection (most commonly viral).
• A medical condition that causes long-lasting inflammation, like rheumatoid arthritis.
• A reaction to a new medication.
• Severe medical illness, such as trauma.
• Had their spleen removed.
• Certain types of cancer, like leukemia or lymphoma.

How is lymphocytosis diagnosed?

Providers rely on your medical history, current symptoms, medication list, and a physical exam to help determine what’s causing lymphocytosis. They may ask questions about your habits and lifestyle to see if you’re at high-risk for certain infections, such as sexually transmitted infections (STIs). They may perform a blood test to check your lymphocyte count.

If your levels are high, your provider may retest later to see if the spike is temporary. If your levels remain high and your provider is unsure why, they may order additional tests. You may be referred to a blood specialist called a hematologist for a diagnosis.

What tests will be done to diagnose lymphocytosis?

Your provider may order a blood test called a complete blood count (CBC) with differential. This test shows if you have a higher-than-normal amount of lymphocytes. They may order a flow cytometry test to see if the lymphocytes are clonal (seen in cancers like chronic lymphocytic leukemia). Testing may also include a bone marrow biopsy to help determine the root cause of lymphocytosis.

How is lymphocytosis treated?

Lymphocytosis treatment involves resolving what’s causing the high lymphocyte count. If your body is producing white blood cells to fight a germ, you may not need treatment. In time, your immune system can usually take care of the issue. If the spike in white blood cells is a sign of cancer, you can discuss treatment options with your provider.

Receiving treatment for the underlying cause can help restore your lymphocyte levels to normal.

What complications are associated with lymphocytosis?

In some cases, lymphocytosis is one of the first signs of certain blood cancers, including chronic lymphocytic leukemia (CLL), the most common type of leukemia in adults. Further tests are usually necessary to rule out other medical conditions and make a firm diagnosis of the cause of lymphocytosis.

Can lymphocytosis be prevented?

Lymphocytosis isn’t preventable. You can reduce your risk by taking steps to keep from getting sick:

• Avoid physical contact with people who have a contagious bug.
• Don’t share personal items with people who are sick.
• Wash your hands frequently and thoroughly with soap and water.
• Disinfect surfaces and commonly used items that may carry germs.

When should I be concerned about lymphocytes?

Contact your provider if you have a persistent infection or experience chronic (ongoing) symptoms or symptoms that get worse over time. Your doctor can determine if you have lymphocytosis during a complete medical examination.

Does lymphocytosis lead to leukemia?

It can, but this is rare. Sometimes monoclonal B-cell lymphocytosis (MBL) progresses to a specific leukemia called chronic lymphocytic leukemia (CLL). A B-cell is a particular type of lymphocyte. With MBL, you have a higher-than-normal amount of clonal B-cells in your blood.