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What is Large granular lymphocytic leukemia and explain in detail?
Large granular lymphocytic (LGL) leukemia is a chronic lymphoproliferative disorder that exhibits an unexplained, chronic (> 6 months) elevation in large granular lymphocytes (LGLs) in the peripheral blood.It is divided in two main categories: T-cell LGL leukemia (T-LGLL) and natural-killer (NK)-cell LGL leukemia (NK-LGLL).  As the name suggests, T-cell large granular lymphocyte leukemia is characterized by involvement of cytotoxic-T cells).In a study based in the US, the average age of diagnosis was 66.5 years whereas in a French study the median age at diagnosis was 59 years (with an age range of 12–87 years old). In the French study, only 26% of patients were younger than 50 years which suggests that this disorder is associated with older age at diagnosis. Due to lack of presenting symptoms, the disorder is likely to be underdiagnosed in the general population.

Signs and symptoms
This disease is known for an indolent clinical course and incidental discovery. The most common physical finding is moderate splenomegaly. B symptoms are seen in a third of cases, and recurrent infections due to anaemia and/or neutropenia are seen in almost half of cases.Rheumatoid arthritis is commonly observed in people with T-LGLL, leading to a clinical presentation similar to Feltys syndrome. Signs and symptoms of anemia are commonly found, due to the association between T-LGLL and erythroid hypoplasia.

Sites of involvement
The leukemic cells of T-LGLL can be found in peripheral blood, bone marrow, spleen, and liver. Nodal involvement is rare.

Cause
The postulated cells of origin of T-LGLL leukemia are transformed CD8+ T-cell with clonal rearrangements of β chain T-cell receptor genes for the majority of cases and a CD8- T-cell with clonal rearrangements of γ chain T-cell receptor genes for a minority of cases.

Diagnosis
Laboratory findings
The requisite lymphocytosis of this disease is typically 2-20x109/L.Immunoglobulin derangements including hypergammaglobulinemia, autoantibodies, and circulating immune complexes are commonly seen.

Peripheral blood
The neoplastic lymphocytes seen in this disease are large in size with azurophilic granules that contains proteins involved in cell lysis such as perforin and granzyme B. Flow cytometry is also commonly used.

Bone marrow
Bone marrow involvement in this disease is often present, but to a variable extent