A Rare Case of T-Large Granular Lymphocytic (T-LGL) Leukemia in a Patient With Rheumatoid Arthritis With Neutropenia and Low LGL Level.

T-large granular lymphocytic (T-LGL) leukemia is a rare hematological malignancy characterized by clonal expansion of cytotoxic T-cells resulting in cytopenias. The diagnostic criteria for T-LGL leukemia necessitated a sustained peripheral blood elevation of LGLs exceeding 2 × 10⁹/L for a minimum duration of 6 months, in the absence of an identifiable etiology. In most of the cases, it is associated with autoimmune disorders such as rheumatoid arthritis. As cytopenias, including neutropenia, can be an early manifestation of the disease, they may get confused with Felty's syndrome, resulting in delayed diagnosis and treatment. Hence, we are presenting a rare case of diagnosing T-LGL leukemia in a patient with rheumatoid arthritis with neutropenia and low LGL level.