Occasionally a patient infected with cytomegalovirus (CMV) may develop a marked lymphocytosis.

Clinical features:

(1) marked lymphocytosis which may persist for some time

(2) evidence of infection with CMV

(3) variable infectious mononucleosis-like syndrome


The proliferation should be polyclonal.


Differential diagnosis:

(1) acute leukemia

(2) other clonal lymphoproliferation

(3) drug reaction


Other infections associated with lymphocytosis:

(1) Epstein Barr virus (EBV)

(2) pertussis

(3) rubella

(4) mumps

(5) viral hepatitis

(6) chickenpox

(7) toxoplasmosis

(8) babesiosis

(9) cat-scratch disease (Bartonella henselae)

(10) HIV (CD8 T-cell lymphocytosis, diffuse infiltrative lymphocytosis syndrome)

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