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. Lymphocytosis, defined by an increase in absolute lymphocyte count (ALC) to more than 4000 lymphocytes/microL in adult patients, is a common hematologic abnormality. This activity reviews the evaluation of patients presenting with lymphocytosis, discusses the differential diagnosis for this condition, and highlights the role of the healthcare team, including primary care physicians and hematologists in evaluating and managing patients with this condition.

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:

• Had a recent infection (most commonly viral)
• A medical condition that causes long-lasting inflammation
• Severe medical illness, such as trauma
• Had their spleen removed
• Certain types of cancer, like leukaemia or lymphoma

SYMPTOMS AND CAUSES

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  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.

DIAGNOSIS AND TESTS

How is lymphocytosis diagnosed?

Your doctor diagnoses lymphocytosis with a blood test called a complete blood count (CBC) with differential. This test shows an increase in white blood cells, with higher than normal amount of lymphocytes. Your doctor may use other diagnostic blood tests, such as a test called flow cytometry, to see if the lymphocytes are clonal (which is seen in a disorder called chronic lymphocytic leukemia). Testing may also include a bone marrow biopsy, to help determine the root cause of lymphocytosis. Doctors rely on your medical history, current symptoms, meication and physical exam to help determine the underlying cause of lymphocytosis.

MANAGEMENT AND TREATMENT

How is lymphocytosis treated?

Doctors treat lymphocytosis by working to resolve its underlying cause. For most people, lymphocytosis goes away as the underlying condition improves.

What complications are associated with lymphocytosis?

Lymphocytosis tells your doctor that you have or have had an infection or illness. In many cases, lymphocytosis simply means your body has been fighting a viral infection.

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

PREVENTION

Can lymphocytosis be prevented?

There is no way to prevent lymphocytosis. You can reduce your risk of viral infection by:

• Frequently and thoroughly washing your hands with soap and water
• Avoiding contact with sick individuals
• Avoiding sharing personal items with people who are sick
• Disinfecting surfaces and commonly used items

OUTLOOK / PROGNOSIS

What is the outcome after treatment of lymphocytosis?

Lymphocytosis usually goes away after treatment for the condition or disease that caused the body to produce extra white blood cells.

LIVING WITH

When should I call my doctor?

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

Best regards,
John Mathews
Editorial Assistant
Journal of Phlebology and Lymphology