Patient presentation:
(1) clinical features (neutropenia with frequent infections; unexplained anemia; presence of rheumatoid arthritis; lymphadenopathy and/or hepatosplenomegaly)
(2) increased large granular lymphocytes in the peripheral blood (absolute count > 500 per µL). A person with <= 500 LGL per µL may also be included if the clinical syndrome is highly characteristic; however, there should be some present (I will use > 300 per µL in the implementation, but this is a guess).
Phenotypic studies on peripheral blood lymphocytes:
Type 1 (T cell): CD3 positive, CD57 positive, CD56 negative (rarely positive)
Type 2 (NK cell): CD3 negative, CD57 negative or weakly positive, CD56 positive
Workup Type 1: Perform rearrangement studies of the T-cell receptor (TCR) gene.
(1) If clonal: T-cell LGL leukemia
(2) If nonclonal: reactive T-cell LGL
Workup Type 2: Evaluate disease course.
(1) If aggressive: natural killer (NK) cell leukemia
(2) If not aggressive: reactive NK cell lymphocytosis (short term, weeks) or chronic NK cell lymphocytosis (long term, months or years).
