If a blood test reveals that your child has an abnormally low number of lymphocytes, you may have questions about what that means and whether it's cause for concern. Read on for answers to common questions about low levels of lymphocytes, also called lymphocytopenia or lymphopenia.
What Do Low Lymphocytes Mean?
What are lymphocytes?
The three main categories of blood cells are red blood cells, white blood cells and platelets. Lymphocytes are a type of white blood cell.
Like all white blood cells, lymphocytes are part of the immune system: They help the body fight diseases, including cancer as well as viral, bacterial, fungal and parasitic infections. There are three types of lymphocytes, each with their own job:
- B cells. B cells make antibodies, proteins that help your body recognize and destroy invading microorganisms, such as bacteria and viruses.
- T cells. T cells kill cells that have become cancerous or infected. They also help B cells make antibodies.
- Natural killer (NK) cells. NK cells contain enzymes that kill virus-infected cells and cancer cells.
What is a normal lymphocyte level?
What's considered normal varies with age.
Newborns and young children have higher numbers of lymphocytes than adults. For adults, a healthy lymphocyte count is usually between 1,000 and 4,800 lymphocytes per microliter of blood. For children age 6 or younger, fewer than 2,000 lymphocytes per microliter of blood may be considered abnormally low.
What causes low lymphocytes?
Lymphocyte counts may temporarily drop due to:
- Infections, such as the flu, sepsis, pneumonia and COVID-19
- Certain medical treatments, including chemotherapy, radiation therapy, steroid medications and major surgery
- Fasting or severe stress
Chronic (long-lasting) lymphopenia can be caused by:
- Undernutrition (not getting enough calories or protein)
- Hereditary immunodeficiency disorders, such as severe combined immunodeficiency
- Autoimmune conditions, including lupus, Sjögren’s syndrome and rheumatoid arthritis
- Certain chronic infections, such as HIV infection
- Certain cancers, such as leukemia and lymphoma
Do low lymphocytes cause symptoms?
Mild lymphopenia may not cause symptoms. In more severe cases, children may have frequent, long-lasting or unusual infections.
The underlying cause of lymphopenia can cause symptoms, such as:
- Cough, runny nose and fever – due to an upper respiratory infection, such as the flu
- Enlarged lymph nodes and spleen – due to cancer or HIV infection
- Small lymph nodes or tonsils – due to a hereditary immune system disorder
- Rashes and joint pain – due to an autoimmune disorder
How are low lymphocytes treated?
Treatment depends on what is causing the low lymphocyte count. If it's due to a short-term illness or medical treatment, it might not need any care. In these cases, lymphocyte levels usually go back to normal once the illness is gone or the treatment ends. Mild cases without an underlying cause may not need treatment either.
If your child has low lymphocyte levels because of a long-term condition, like an immunodeficiency disorder, their doctor will focus on treating that condition.
Although low lymphocyte levels can result from an infection, they also increase the risk of infections. For this reason, some children need therapies to prevent or treat infections. Those who struggle with frequent infections may be given immunoglobulin therapy, which boosts the immune system. Children with a hereditary immunodeficiency disorder may benefit from a stem cell transplant.
What about high lymphocytes?
Some of the same conditions that lead to lymphopenia can cause abnormally high lymphocyte levels. These include:
- Viral infections, such as mononucleosis
- Bacterial infections
- Lymphoma
- Lymphocytic leukemias
Most often, high lymphocytes are seen because the body is fighting off a viral infection.
This information is for educational purposes only and is not intended to replace the advice of your child's doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your child's provider.
