A Rare Case of Acute Myeloid Leukemia Initially Presenting With Fever of Unknown Origin and Rapidly Progressing Pericardial Effusion.

This case report highlights a patient who had persistent fevers for weeks and rapidly progressing pericardial effusion following a positive test for coronavirus disease 2019 (COVID-19) two weeks before presentation to the hospital. The initial thought was that her fever was of infectious etiology, but relevant investigations led to the diagnosis of acute myeloid leukemia (AML). AML, which is characterized by clonal expansion of immature "blast cells" in the peripheral blood and bone marrow resulting in ineffective erythropoiesis and bone marrow failure, is the most prevalent form of leukemia. It is the most aggressive form of leukemia, which has varying prognoses determined by the subtypes. This report explores the association between AML, fever of unknown origin, and pericardial effusion, shedding light on a notable clinical aspect. Fever in AML may be attributed to underlying inflammatory processes, cytokine dysregulation, or bone marrow failure. Recognition of fever as a potential indicator of AML contributes to enhanced clinical vigilance. Pericardial effusions and cardiac tamponade, although rare, can be a presenting feature of AML, and can present side by side with fever of unknown origin as seen in this case report.