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Chapter 49: Lymphocytosis and Lymphocytopenia

LYMPHOCYTOSIS

Definition

  • 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.

TABLE 49–1CAUSES OF LYMPHOCYTOSIS
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TABLE 49–1 CAUSES OF LYMPHOCYTOSIS

  1. Primary lymphocytosis

    1. Lymphocytic malignancies

      1. Acute lymphocytic leukemia (Chap. 54)

      2. Chronic lymphocytic leukemia and related disorders (Chap. 55)

      3. Prolymphocytic leukemia (Chap. 54)

      4. Hairy cell leukemia (Chap. 56)

      5. Adult T-cell leukemia (Chaps. 54 and 66)

      6. Leukemic phase of B-cell lymphomas (Chaps. 60, 61)

      7. Large granular lymphocytic leukemia (Chaps. 57, 66)

        1. Natural killer (NK) cell leukemia (Chap. 66)

        2. CD8+ T-cell large granular lymphocytic leukemia (Chap. 66)

        3. CD4+ T-cell large granular lymphocytic leukemia (Chap. 66)

        4. γ/δ T-cell large granular lymphocytic leukemia (Chap. 66)

    2. Monoclonal B-cell lymphocytosis (Chap. 55)

    3. Persistent polyclonal B cell lymphocytosis

  2. Reactive lymphocytosis

    1. Mononucleosis syndromes (Chap. 52)

      1. Epstein-Barr virus

      2. Cytomegalovirus

      3. Human immunodeficiency virus

      4. Herpes simplex virus type II

      5. Rubella virus

      6. Toxoplasma gondii

      7. Adenovirus

      8. Infectious hepatitis virus

      9. Dengue fever virus

      10. Human herpes virus type 6 (HHV-6)

      11. Human herpes virus type 8 (HHV-8)

      12. Varicella zoster virus

    2. Bordetella pertussis

    3. NK cell lymphocytosis (see Chap. 57)

    4. Stress lymphocytosis (acute)

      1. Cardiovascular collapse

        1. Acute cardiac failure

        2. Myocardial infarction

      2. Staphylococcal toxic shock syndrome

      3. Drug-induced

      4. Major surgery

      5. Sickle cell crisis

      6. Status epilepticus

      7. Trauma

    5. Hypersensitivity reactions

      1. Insect bite

      2. Drugs

    6. Persistent lymphocytosis (subacute or chronic)

      1. Cancer

      2. Cigarette smoking

      3. Hyposplenism

      4. Chronic infection

        1. Leishmaniasis

        2. Leprosy

        3. Strongyloidiasis

      5. Thymoma

Source: Williams Hematology, 9th ed, Table 79–1.

Primary Clonal Lymphocytosis

  • 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 ...

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