Aggressive NK-cell leukemia

Aggressive NK-cell leukemia is a disease with an aggressive, systemic proliferation of natural killer cells (NK cells) and a rapidly declining clinical course.aggressive: Sézary disease Aggressive NK-cell leukemia is a disease with an aggressive, systemic proliferation of natural killer cells (NK cells) and a rapidly declining clinical course. It is also called aggressive NK-cell lymphoma. Patients usually present with constitutional symptoms (malaise, weight loss, fatigue), and hepatosplenomegaly is commonly found on physical exam. Lymphadenopathy is also found to a lesser extent. Due to the aggressive nature of the disease, patients may initially present at a more advanced stage, with coagulopathies, hemophagocytic syndrome, and multi-organ failure. Rarely, individuals who have an aggressive NK cell lymphoma that is associated with latent infection with the Epstein-Barr virus (see next section) present with or develop extensive allergic reactions to mosquito bites. The symptoms of these reactions range from a greatly enlarged bite site that may be painful and involve necrosis to systemic symptoms (e.g. fever, swollen lymph nodes, abdominal pain, and diarrhea), or, in extremely rare cases, to life-threatening anaphylaxis. This disease has a strong association with the Epstein-Barr virus (EBV), but the true pathogenesis of this disease has yet to be described. The cell of origin is believed to be an NK cell. Blastoid NK cell lymphoma appears to be a different entity and shows no association with EBV. This disease is typically found and diagnosed in peripheral blood, and while it can involve any organ, it is usually found in the spleen, liver, and bone marrow. Leukemic cells are invariably present in samples of peripheral blood to a variable extent. Pancytopenia (anemia, neutropenia, thrombocytopenia) is commonly seen as well. The leukemic cells have a diameter mildly greater than a large granular lymphocyte (LGL) and have azurophilic granules and nucleoli of varying prominence. Nuclei may be irregular and hyperchromatic. Bone marrow involvement runs the spectrum between an inconspicuous infiltrate to extensive marrow replacement by leukemic cells. Reactive histiocytes displaying hemophagocytosis can be seen interspersed in the neoplastic infiltrate. Leukemic involvement of organs is typically destructive on tissue sections with necrosis and possibly angioinvasion, and the monotonous infiltrate may be diffuse or patchy.