Infectious mononucleosis is defined as any blood lymphocytosis induced in response to an infectious agent.
Usually greater than 50% of the circulating white cells are lymphocytes, more than 10% of which have the morphology of reactive lymphocytes (Figure 52–1).
Table 52–1 lists the etiologic agents that produce mononucleosis.
— A sore throat is preceded by 1 to 2 weeks of lethargy.
— Epstein-Barr virus (EBV) generally is the cause.
Glandular form without pharyngitis:
— Lymph node enlargement occurs.
— The usual cause is agents other than EBV (eg, Toxoplasma gondii).
— Lethargy with fever or diarrhea without pharyngitis, usually as a consequence of cytomegalovirus (CMV), is characteristic.