The clonal proliferation of T cells is known as T-cell large granular lymphocyte (LGL). Anemia, neutropenia, and thrombocytopenia can be caused by it. Autoimmune disorders, particularly rheumatoid arthritis, and other disorders are regularly linked with T-cell LGL. A flow cytometry that demonstrates CD8+CD57+ T cells’ expansion helps suggest this diagnosis. The T-cell receptor gene rearrangements studies help establish it further. A disorder of the dysregulation of apoptosis through abnormalities in the Fas/Fas ligand pathway is the large granular lymphocyte leukemia as suggested by increasing proof. It is an indolent disorder in a majority of patients. Immunosuppressive agents, such as steroids, methotrexate, cyclophosphamide, and cyclosporine A can be used to attain a substantial improvement of cytopenias. The research delivers a succinct, recent summary of large granular lymphocyte leukemia. In addition, it also provides further details about the associated, more aggressive, malignancies of cytotoxic T cells and natural killer cells.