Aggressive Natural Killer Cell Leukemia: A Rare and Rapidly Progressive Hematologic Malignancy-Case Report and Literature Review.

Aggressive natural killer cell leukemia (ANKL) is a rare, fulminant hematologic malignancy characterized by neoplastic proliferation of mature NK cells. It is frequently associated with Epstein-Barr virus (EBV) infection, although EBV-negative cases have also been reported. While typically observed in young to middle-aged adults of East Asian descent, increasing recognition has led to identification of ANKL across diverse age groups and ethnicities. The disease is defined by a rapid clinical course and poor prognosis, underscoring the importance of early diagnosis and effective treatment. We present a case of a 71-year-old Caucasian male who developed fever, altered mental status, hepatosplenomegaly, pancytopenia, and hemophagocytic lymphohistiocytosis (HLH) and who was ultimately diagnosed with ANKL. Although he demonstrated initial clinical improvement with chemotherapy, relapse of the ANKL ensued a few months later, and he ultimately succumbed to progressive disease. A review of current literature is provided, focusing on molecular pathogenesis and emerging therapeutic strategies.