Cause and Diagnosis of Lymphopenia

White blood cell loss primarily related to infection

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Lymphopenia (also known as lymphocytopenia) is a term used to describe the state where you don't have a certain type of blood cell called a lymphocyte. Lymphocytes are one of three types of white blood cell (known as leukocytes) found in blood. Leukocytes function as part of our body’s first-line immune defense against disease-causing pathogens such as bacteria, viruses, and parasites.

Lymphopenia is most often caused by infection, including the common cold, and will usually recover on its own once the infection has cleared.

In cases where the cause is idiopathic (of unknown origin), it may suggest a more serious underlying condition.

Understanding Lymphocytes and Lymphopenia

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 25 and 45 percent.

Lymphocytes can be further broken down into three subsets:

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

As such, 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.

Causes of Lymphopenia

Lymphopenia can be caused by many conditions, including infection and medication side effect.

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

Diseases or Conditions Related to Lymphopenia

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 

What a Low White Blood Cell Count Tells Us

A low white blood cell count is most often detected when your doctor orders 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 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 this happens, 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.

Source:

Janeway, C.; Travers, P.; Walport, M.; et al. Immunobiology (5th ed.) New York and London: Garland Science; ISBN 0-8153-4102-6.

Regent, A.; Autran, B.; Carcelain, G.; et al. “Idiopathic CD4 lymphocytopenia: clinical and immunologic characteristics and follow-up of 40 patients.” Medicine. 2014; 93(2):61-72.

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