MayoClinic.com reprints
This single copy is for your personal, noncommercial use only. For permission to reprint multiple copies or to order presentation-ready copies for distribution, use the reprints link below.
· Order reprints of this article now.
Lymphocytosis (high lymphocyte count)
By Mayo Clinic staffMayo Clinic Health Manager
Get free personalized health guidance for you and your family.
Get Started
About our e-newsletters
- Free e-newsletters
- Mayo Clinic expertise
- We do not share your e-mail address
Housecall, our weekly general-interest e-newsletter, keeps you up to date on a wide variety of health topics with timely, reliable, practical information, recipes, blogs, questions and answers with Mayo Clinic experts and more. Our biweekly topic-specific e-newsletters also include blogs, questions and answers with Mayo Clinic experts, and other useful information that will help you manage your health.
Housecall Archives
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
Definition
Lymphocytosis, or high lymphocyte count, is an increase in white blood cells called lymphocytes (LIM-foe-sites). There are five primary subtypes of white blood cells, each with a different disease-fighting activity.
There are two major types of lymphocytes. T lymphocytes, or T cells, identify foreign substances in your body and begin an immune response. B lymphocytes, or B cells, produce antibodies to foreign substances. In autoimmune disorders, lymphocyte cells misidentify some of your own tissues as foreign substances.
A count of more than 2,900 lymphocytes in a microliter of blood is generally considered to be lymphocytosis in adults. However, the threshold for lymphocytosis varies from one medical practice to another. In children the threshold for lymphocytosis varies with age.
Causes
You may have a lymphocyte count that exceeds the typical threshold but have no disease present. Your doctor makes a judgment about whether the count is "too high" based on other factors, such as symptoms you may be experiencing and the results of other tests.
If your doctor determines your lymphocyte count is high, the test result may be evidence of one of the following conditions:
- Severe viral infection
- Cancer of the blood or lymphatic system
- An autoimmune disorder causing ongoing (chronic) inflammation
Specific causes of lymphocytosis include:
When to see a doctor
A high lymphocyte count is usually found when your doctor has ordered tests to help diagnose a condition you're already experiencing. It's rarely an unexpected finding or simply discovered by chance. Talk to your doctor about what these results mean. A high lymphocyte count and results from other tests may already indicate the cause of your illness, or your doctor may suggest other tests to assess your condition.
- Laboratory reference values. Lymphocyte. Rochester, Minn.: Mayo Foundation for Medical Education and Research; Oct. 2008.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2007.
- Pagana K, et al. Mosby's Manual of Diagnostic and Laboratory Tests. St. Louis, Mo.: Mosby, Inc.; 2002.
