What Is Lymphopenia?

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Lymphopenia (also known as lymphocytopenia) is a blood disorder that involves a reduced level of white blood cells (WBC) known as lymphocytes.

Lymphocytes are an important part of the immune system, serving as the body’s first-line defense against disease-causing pathogens such as bacteria, viruses, and parasites.

Lymphopenia is most often caused by infections, such as influenza or COVID-19. It typically resolves on its own once the infection has cleared. Sometimes lymphopenia is caused by an unknown origin, which may suggest a more serious underlying condition.

This article explains lymphopenia, its causes, and related conditions.

Close up of scientists hands selecting a blood sample for medical testing
Andrew Brookes / Getty Images


The vast majority of cells in our blood are erythrocytes (red blood cells) which are responsible for transporting oxygen throughout the body. This is followed by thrombocytes (platelets) and leukocytes.

Leukocytes are produced in the bone marrow and circulate freely in the bloodstream as part of the immune system. Lymphocytes represent the largest proportion of these cells, ranging anywhere from 20% and 40%.

Lymphocytes can be further broken down into three subsets:

  • Natural killer (NK) cells serve as the first line of defense for the immune system.
  • T cells are produced in response to a specific pathogen.
  • B cells produce antibodies that help other cells identify and neutralize pathogens.

Lymphopenia may be identified by the type of lymphocyte affected. For example, HIV specifically targets CD4 T cells for infection, resulting in massive losses of that specific cell. The loss of B cells is more associated with immune-suppressive drugs (such as those used for organ recipients) while NK depletion is typically a rare situation.


Lymphopenia can be caused by many conditions, including infection and medication side effects. At times, the condition may only affect lymphocytes. In others, it can be the result of a depletion of all white blood cells.

For instance, when the treatment for viral hepatitis includes peginterferon and ribavirin, it can cause suppression of just neutrophils (neutropenia) or just lymphocyte (lymphopenia) in some people. In others, it can affect the entire range of white blood cells (leukopenia).

Lymphopenia is most associated with conditions that affect the bone marrow, including:

  • Viral infections that temporarily disrupt bone marrow function
  • Congenital disorders that involve diminished bone marrow function
  • Cancer or other diseases that damage bone marrow
  • Autoimmune disorders that destroy white blood cells or bone marrow cells
  • Acute infections that kill off white blood cells faster than they can be produced
  • Medications, such as antibiotics, that can destroy white blood cells

Related Conditions

The diseases and conditions most commonly associated with lymphopenia can broadly be described as either being pathogenic (related to infection), cytotoxic (toxic to cells), congenital (caused by genetic defect), or nutritional.

They include:

  • Aplastic anemia: A rare condition where the body stops producing blood cells
  • Chemotherapy
  • HIV
  • Hypersplenism: The premature destruction of blood cells by the spleen
  • Leukemia: A type of blood cancer
  • Lupus: An autoimmune disorder
  • Malnutrition and vitamin deficiencies
  • Myelodysplastic syndromes: A group of disorders which disrupt the production of blood cells
  • Rheumatoid arthritis: Another autoimmune disorder
  • Radiation therapy
  • Tuberculosis 

Low White Blood Cell Count

An overall low white blood cell count (leukopenia) is most often detected when your healthcare provider orders a test for a condition you're already experiencing. A low count is rarely an unexpected finding.

In some cases, the type of white blood cell affected may be enough to point you in the direction of a diagnosis. At other times, you may need additional tests to piece together a cause.

A severely low white blood cell count makes places you at greater risk of infection.

If your white blood cell count is very low, you may need to take special precautions to prevent illness. This includes avoiding others who may be ill, washing your hands regularly and thoroughly, or even wearing a face mask if you are in a confined space (such as an airplane) with others.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Territo M. Lymphocytopenia. Merck Manual Professional Version. Kenilworth, NJ: Merck & Co., Inc.; 2019.

  3. National Cancer Institute. Seer Training Modules. Composition of the blood.

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Additional Reading

By Charles Daniel
 Charles Daniel, MPH, CHES is an infectious disease epidemiologist, specializing in hepatitis.