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DEFINITION

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  • T-cell large-granular lymphocytic (T-LGL) leukemia results from the clonal expansion of large granular lymphocytes (LGL) with a T-cell (CD3+) phenotype and a clonal T-cell receptor gene rearrangement(s).

  • Natural killer (NK)-LGL leukemia is a clonal expansion of LGL with a NK cell (CD3-) phenotype. It lacks convenient markers to determine clonality such as antigen receptor rearrangements.

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T-LGL LEUKEMIA

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Etiology and Pathogenesis

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  • Suggestive evidence of a role for human T lymphotropic virus (HTLV) retroviral infection in some patients.

  • Most patients are not infected with either HTLV-I or HTLV-II.

  • Cytomegalovirus implicated in rare cases of CD4+ T-LGL.

  • Epstein-Barr virus implicated in some cases of NK-LGL.

  • Leukemic cells have features of antigen-activated cytotoxic T lymphocytes (CTL), suggesting role for antigen in initial LGL expansion.

  • Constitutive overexpression of the Fas ligand (CD178), which also is found at high levels in patients' sera, may be a factor in many disease manifestations (e.g., neutropenia, rheumatoid arthritis).

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Clinical Features

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  • About half of patients have palpable splenomegaly.

  • About one-third of patients have recurrent bacterial infections and/or "B symptoms" (e.g., low-grade fevers, night sweats, and/or weight loss) (aggressive variant) (see Table 58–1).

  • About one-quarter of patients have rheumatoid arthritis, often with features of "Felty syndrome."

  • Less than 10 percent of patients have lymphadenopathy.

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Table Graphic Jump Location
TABLE 58–1COMPARATIVE FEATURES OF LARGE GRANULAR LYMPHOCYTIC LEUKEMIA
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Laboratory Features

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  • Immunophenotype of LGL cells in blood and marrow: CD3+CD8+CD16+ CD57+ CD4-CD56-, and, often, HLA-DR+.

  • Patients have clonal T-cell–receptor gene rearrangement(s), usually involving α and β chains.

  • Nearly 85 percent of patients have neutropenia, often less than 0.5 × 109/L.

  • Approximately half of the patients have anemia, often caused by pure red cell aplasia and/or autoimmune hemolytic anemia.

  • Approximately one-fifth of patients have thrombocytopenia.

  • About one-quarter of patients do not have increased blood total lymphocyte counts.

  • The median LGL count in patients is 4.0 × 109/L (normal mean 0.3 ×109 /L) (Fig. 58–1...

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