Absolute lymphocytosis may be associated with many conditions.

Absolute lymphocytosis is when the absolute lymphocyte count is above the upper limit of normal for age, gender, and race.


absolute lymphocyte count =

= (white blood cell count per µL) * (percent lymphocytes) / 100


Absolute lymphocytosis needs to be distinguished from relative lymphocytosis, where the percent lymphocytes is increased but the absolute lymphocyte count is low or normal.


An absolute lymphocytosis may be classified clinically as:

(1) transient versus persistent

(2) progressive


The most common cause of lymphocytosis is viral infection:

(1) infectious mononucleosis

(2) cytomegalovirus (CMV)

(3) enterovirus

(4) HIV

(5) viral hepatitis

(6) influenza

(7) measles

(8) mumps

(9) rubella

(10) varicella



Other causes of lymphocytosis:

(1) other infections (pertussis, brucellosis, syphilis, toxoplasmosis)

(2) drug hypersensitivity reaction

(3) persistent polyclonal lymphocytosis

(4) trauma or physiological stress

(5) clonal lymphoproliferative disorder

(5a) acute lymphoblastic leukemia (ALL)

(5b) chronic lymphocytic leukemia (CLL)

(5c) other

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