Lymphopenia

Lymphopenia is a decrease in the total number of lymphocytes (< 1000/μl in adults or < 3000/μl in children under 2 years of age).

Consequences of lymphopenia include the development of opportunistic infections and an increased risk of cancer and autoimmune diseases. If lymphopenia is detected during a complete blood count, diagnostic tests for immunodeficiency conditions and lymphocyte subpopulation analysis are necessary. Treatment is aimed at the underlying disease.

The normal lymphocyte count in adults is 1000 to 4800/μl, in children under 2 years of age from 3000 to 9500/μl. At the age of 6 years, the normal lower limit of lymphocytes is 1500/μl. Both T- and B-lymphocytes are present in the peripheral blood. About 75% are T-lymphocytes and 25% are B-lymphocytes. Since the proportion of lymphocytes is only 20-40% of the total number of leukocytes in the blood, lymphopenia may not be detected in a blood test without determining the leukocyte formula.

Almost 65% of blood T cells are CD4 T lymphocytes (helpers). Most patients with lymphopenia have a decrease in the absolute number of T cells, especially the number of CD4 T cells. The average number of CD4 T cells in adults is 1100/μl (from 300 to 1300/μl), the average number of another major subpopulation of T lymphocytes, CD8 T cells (suppressors) is 600/μl (from 100 to 900/μl).

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Causes of lymphopenia

Congenital lymphopenia occurs in congenital immunodeficiency diseases and diseases in which there is a violation of lymphocyte production. In some hereditary diseases, such as Wiskott-Aldrich syndrome, there is a deficiency of adenosine deaminase, purine nucleoside phosphorylase, and there is increased destruction of T-lymphocytes. In many hereditary diseases, there is also a deficiency of antibodies.

Acquired lymphopenia occurs in a wide variety of diseases. Worldwide, the most common cause of lymphopenia is protein malnutrition. The most common infectious disease causing lymphopenia is AIDS, in which HIV-infected CD4 T cells are destroyed. Lymphopenia may result from impaired lymphocyte production due to damage to the structure of the thymus or lymph nodes. In acute viremia caused by HIV or other viruses, lymphocytes may be subject to accelerated destruction due to the active infection, be captured by the spleen or lymph nodes, or migrate to the respiratory tract.

Long-term psoriasis therapy with psoralen and ultraviolet radiation may destroy T cells.

Iatrogenic lymphopenia is caused by cytotoxic chemotherapy, radiation therapy, or administration of antilymphocyte immunoglobulin. Glucocorticoids can induce lymphocyte destruction.

Lymphopenia may occur in autoimmune diseases such as SLE, rheumatoid arthritis, myasthenia gravis, and protein-losing enteropathy.

Causes of lymphopenia

Congenital

Acquired

Lymphopoietic stem cell aplasia. Ataxia-telangiectasia. Idiopathic CD4 + T-lymphopenia. Immunodeficiency in thymoma. Severe combined immunodeficiency associated with an abnormality in the γ-chain of the interleukin-2 receptor, ADA or PNP deficiency, or unknown etiology. Wiskott-Aldrich syndrome

Infectious diseases, including AIDS, hepatitis, influenza, tuberculosis, typhoid fever, sepsis. Malnutrition due to alcohol consumption, inadequate protein intake or zinc deficiency. Iatrogenic following cytotoxic chemotherapy, glucocorticoids, high doses of psoralen and ultraviolet irradiation, immunosuppressive therapy, radiation or thoracic duct drainage. Systemic diseases with autoimmune components: aplastic anemia, Hodgkin's lymphoma, myasthenia gravis, protein-losing enteropathy, rheumatoid arthritis, SLE, thermal trauma

ADA - adenosine deaminase; PNP - purine nucleoside phosphorylase.

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Symptoms of lymphopenia

Lymphopenia itself is usually asymptomatic. However, signs of associated diseases, absence or reduction of tonsils or lymph nodes indicate cellular immunodeficiency. The most common symptoms of lymphopenia are skin diseases such as alopecia, eczema, pyoderma, telangiectasia; signs of hematological diseases such as pallor, petechiae, jaundice, ulceration of the oral mucosa; generalized lymphadenopathy and splenomegaly, which may indicate the presence of HIV infection.

Patients with lymphopenia have frequent recurrent infections or infections with rare organisms such as Pneumocystis proven (formerly P. carinii), cytomegalovirus, rubella, and varicella with pneumonia and lymphopenia, suggesting immunodeficiency. In patients with lymphopenia, lymphocyte subset counts and immunoglobulin levels should be measured. Patients with frequent recurrent infections should have a complete laboratory evaluation to evaluate for immunodeficiency, even if initial screening tests are normal.

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Treatment of lymphopenia

Lymphopenia disappears when the causative factor or disease that caused it is eliminated. Intravenous immunoglobulin is indicated if the patient has chronic IgG deficiency, lymphopenia, and recurrent infections. Hematopoietic stem cell transplantation can be successfully used in patients with congenital immunodeficiency.

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