Chronic natural killer cell lymphocytosis: a descriptive clinical study

Area of Science:

• Hematology
• Immunology
• Oncology

Background:

• Chronic natural killer (NK) cell lymphocytosis is a rare condition.
• Large granular lymphocyte (LGL) proliferation can involve T-cells or NK cells.
• Distinguishing between T-LGL and NK-LGL is crucial for prognosis and treatment.

Purpose of the Study:

• To review the clinical manifestations and long-term outcomes of patients with chronic NK cell lymphocytosis.
• To compare the characteristics of NK-LGL with T-LGL leukemia.
• To identify key clinical features and treatment responses in chronic NK cell lymphocytosis.

Main Methods:

• Review of over 1,500 peripheral blood lymphoid flow cytometry reports and molecular genetics data.
• Identification of 10 patients with persistent NK cell excess (CD3-CD16+).
• Comparison of clinical data from NK-LGL patients with 68 patients diagnosed with T-LGL leukemia.

Main Results:

• All 10 identified patients with chronic NK cell lymphocytosis are alive with a median disease duration of 5 years.
• Associated conditions included pure red blood cell aplasia, neutropenia, sepsis, and vasculitic syndromes, all responsive to immunosuppressive therapy.
• Compared to T-LGL leukemia, NK-LGL showed similar lymphocyte counts, associated conditions, treatment response, and survival, but with less neutropenia and anemia.

Conclusions:

• Chronic NK cell lymphocytosis is a distinct clinical entity with a favorable long-term outlook.
• Immunosuppressive therapy is effective for managing associated autoimmune and cytopenic manifestations.
• NK-LGL leukemia shares similarities with T-LGL leukemia but presents with a potentially milder hematological profile.