Relative lymphocytosis occurs when there is a higher proportion (greater than 40%) of lymphocytes among the white blood cells, while the absolute lymphocyte count (ALC) is normal (less than 4000 per microliter). Relative lymphocytosis is normal in children under age 2.
Lymphocytosis is an increase in the number or proportion of lymphocytes in the blood. In absolute lymphocytosis, the total lymphocyte count is elevated. In adults, absolute lymphocytosis is present when the absolute lymphocyte count is greater than 4000 per microliter, in older children greater than 7000 per microliter and in infants greater than 9000 per microliter. Lymphocytes normally represent 20 to 40% of circulating white blood cells.
What’s the Reasons of Lymphocytosis ?
Lymphocytosis is the name used when someone has more than a normal level of lymphocytes (T and B helper cells) in the body. The lymphocytes normally fight off viral infections. Children under the age of 5 tend to have large amounts of these. Normally 30% of the body’s WBC’s are only lymphs. In a child they are normally in the 60 – 70% range. And that is normal.
There are two main types of lymphocytes T-cells and B-cells. T-cells are involved in the initial immune response. They identify foreign proteins (antigens). B-cells produce antibodies in response to the presence of identified antigens. Conditions that are commonly associated with lymphocytosis include severe viral infections, cancers (leukemia & lymphoma), vasculitis, autoimmune diseases that cause chronic inflammation & tuberculosis.
Lymphocytosis in Adults
The normal range for the Absolute Lymphocyte Count is age related.
In adults the normal range is 1.5 – 3.5 x 109 /L
Lymphocytosis is defined as a lymphocyte count > 5 x 109 /L
What are the main causes of Lymphocytosis?
Over 80% of patients have lymphocytosis as an incidental finding on a routine full blood count for unrelated symptoms or as part of health screening.
- Transient, reactive lymphocytosis is frequently seen in acute self-limiting viral infection, particularly infectious mononucleosis, and in smokers.
- Chronic infections like tuberculosis, brucellosis, secondary syphilis
- Leukaemia and occasionally lymphoma. Chronic lymphocytosis is characteristic of chronic lymphocytic leukaemia, the incidence of which peaks between 60 and 80 years of age. In its early stages this condition is frequently asymptomatic and treatment is only required in significant progression which is about 1% per year.
Lymphocytosis in Children
Why do young children normally have a high lymphocyte count?
In children, a “high lymphocyte count” can mean 2 different things. One is an absolute increase in total lymphocytes, as may be seen in infections, or a relative (percentage) lymphocytosis which is normal in infants. Lymphocytosis is an increase in the number or proportion of lymphocytes in the blood, usually detected when a complete blood count is routinely obtained. Lymphocytes normally represent 20 to 40% of circulating white blood cells.
The absolute lymphocyte count (ALC) can be directly measured by flow cytometry, or calculated by multiplying the total white blood cell (WBC) count by the percentage of lymphocytes found in the differential count. In absolute lymphocytosis, the total lymphocyte count is elevated. In relative lymphocytosis, there is a higher proportion of lymphocytes among the white blood cells, but a normal absolute number of lymphocytes. In adults, absolute lymphocytosis is present when the absolute lymphocyte count is greater than 4000 per microliter, while relative lymphocytosis is present if the ALC is normal but the differential percentage of lymphocytes is higher than 40%. Relative lymphocytosis is normal in children under age 2.