[4] Patients usually present with constitutional symptoms (malaise, weight loss, fatigue), and hepatosplenomegaly is commonly found on physical exam.

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.

[1][2][5][6][7] 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.

[4] The leukemic cells have a diameter mildly greater than a large granular lymphocyte (LGL) and have azurophilic granules and nucleoli of varying prominence.

[4] Leukemic involvement of organs is typically destructive on tissue sections with necrosis and possibly angioinvasion, and the monotonous infiltrate may be diffuse or patchy.

[4] The genome of the Epstein Barr virus (EBV) is detected in many cases,[9] along with a variety of chromosomal abnormalities.