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Causes of high and low lymphocyte counts
Last reviewed: 06.07.2025
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Absolute lymphocytosis (increased lymphocytes): the absolute number of lymphocytes in the blood exceeds 4×10 9 /L in adults, 9×10 9 /L in young children, and 8×10 9 /L in older children.
In clinical practice, lymphocytes are elevated in leukemoid reactions of the lymphatic type, when the blood picture resembles that of acute or chronic leukemia. Leukemoid reactions of the lymphatic type most often develop in infectious mononucleosis, but are sometimes also possible in tuberculosis, syphilis, brucellosis. The blood picture in acute infectious mononucleosis is characterized by high leukocytosis due to lymphocytes. Lymphocytes in infectious mononucleosis acquire morphological diversity. A large number of atypical lymphocytes appear in the blood, characterized by nuclear dysplasia and an increase in cytoplasm and acquiring a resemblance to monocytes.
Absolute lymphopenia (low lymphocytes) - the number of lymphocytes in the blood is less than 1×10 9 /l - occurs in some acute infections and diseases. Lymphopenia (lymphocytes are lowered) in the initial stage of the infectious-toxic process, which is associated with the migration of lymphocytes from the blood to tissues to the foci of inflammation.
Diseases and conditions accompanied by changes in lymphocyte content
Absolute lymphocytosis |
Absolute lymphopenia |
Viral infection |
Pancytopenia |
Acute infectious lymphocytosis |
Taking glucocorticosteroids |
Whooping cough |
Severe viral diseases |
Infectious mononucleosis |
Malignant neoplasms |
Acute viral hepatitis |
Secondary immunodeficiencies |
CMV infection |
Renal failure |
Chronic lymphocytic leukemia |
Circulatory failure |
Waldenstrom's macroglobulinemia |