Color Atlas of Hematology - Practical Microscopic and Clinical ...

68Abnormalities of the White Cell SeriesExamples of Extreme Lymphocytic Stimulation:Infectious MononucleosisEpstein–Barr virus infection should be considered when, after a prodromalfever of unknown origin, there are signs of enlarged lymph nodes anddeveloping angina, and the blood analysis shows predominantly mononuclearcells and a slightly, or moderately, elevated leukocyte count. Varyingproportions of the mononuclear cells (at least 20%) may be rather extensivelytransformed round cells (Pfeiffer cells, virocytes). Immunologicalmarkers are necessary to ascertain that these are stimulated lymphocytes(mostly T-lymphocytes) defending the B-lymphocyte stem populationagainst the virus attack. The nuclei of these stimulated lymphocytes aretwo- to three-fold larger than those of normal lymphocytes and theirchromatin has changed from a dense and coarse structure to a looser,more irregular organization. The cytoplasm is always relatively wide andmore or less basophilic with vacuoles. Granules are absent. A small proportionof cells appear plasmacytoid. In the course of the disease, thedegree of transformation and the proportions of the different cell morphologieschange almost daily. A slight left shift and elevated monocytecount are often found in the granulocyte series.Acute leukemia is often considered in the differential diagnosis in additionto other viral conditions, because the transformed lymphocytes canresemble the blasts found in leukemia. Absence of a quantitative reductionof hematopoiesis in all the blood cell series, however, makes leukemiaunlikely, as do the variety and speed of change in the cell morphology. Finally,serological tests (EBV antigen test, test for antibodies, and, if indicated,quick tests) can add clarification.Where serological tests are negative, the cause of the symptoms is usuallycytomegalovirus rather than EBV.Characteristics of Infectious MononucleosisAge of onset: School ageClinical findings: Enlarged lymph nodes (rapid onset), inflammationsof throat and possibly spleen CBC: Leukocytes , stimulated lymph nodes, partially lymphoblasts(hematocrit and thrombocytes are normal)Further diagnostics: EBV serological test (IgM +), transaminases usuallyDifferential diagnosis: Lymphomas (usually without fever), leukemia(usually Hb , thrombocytes ) Persistent disease (more than 3weeks): possibly test for blood cell markers, lymph node cytology( histology)Course, treatment: Spontaneous recovery within 2–4 weeks; generalpalliation