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LYMPHOCYTOSIS

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Definition

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  • In adults, the absolute lymphocyte count exceeds 4.0 × 109/L.

  • Normal lymphocyte count in childhood is higher than adults (mean ~6.0 × 109/L) (see Chap. 1).

  • Table 49–1 lists conditions associated with lymphocytosis.

  • Examine blood film to determine if there is abnormal prevalence of:

    — Reactive lymphocytes, associated with infectious mononucleosis (see Chap. 52)

    — Large granular lymphocytes, associated with large granular lymphocyte leukemia (see Chap. 57)

    — Small lymphocytes and smudge cells, associated with chronic lymphocytic leukemia (CLL) (see Chap. 55)

    — Small cleaved lymphocytes, associated with low- or intermediate-grade lymphomas (see Chap. 61)

    — Blasts, associated with acute lymphocytic leukemia (see Chap. 54)

  • Several key tests permit discrimination between polyclonal and monoclonal disorders. Flow cytometric immunophenotyping of cell surface markers (CD), serum protein electrophoresis and immunofixation for monoclonal immunoglobulins, studies of T-cell–receptor gene rearrangement, or clonal cytogenetic findings can distinguish monoclonal lymphocytosis (B or T lymphocytic leukemia or lymphoma) from polyclonal (reactive) lymphocytosis.

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Table Graphic Jump Location
TABLE 49–1CAUSES OF LYMPHOCYTOSIS
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Primary Clonal Lymphocytosis

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  • Neoplastic (monoclonal) proliferation of B cells, T cells, or natural killer (NK) cells

  • Monoclonal B-cell lymphocytosis (see Chap. 55)

    — There are no associated clinical manifestations.

    — Some patients may develop CLL or another type of progressive lymphoproliferative disease (see Chap. 55).

  • Chronic natural killer (NK) cell lymphocytosis (see Chap. 57)

    — CD3–CD16+CD56+ lymphocytes are present.

    — Approximately 60% of cases have no other signs or ...

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