Multiorgan Failure in Hemophagocytic Lymphohistiocytosis Secondary to Acute Monocytic Leukemia and Myocarditis in a Pediatric Patient

Acute monocytic leukemia (AML), a subtype of acute myeloid leukemia, is a rare leukemia found in children. It occurs more frequently in adults over the age of 60. Myocarditis represents inflammation of the muscular layer of the heart, the myocardium causing weakening of the muscles that can lead to hemodynamic instability from a reduced ejection fraction. Myocarditis in the pediatric population is most commonly secondary to a viral or infectious etiology. Hemophagocytic lymphohistiocytosis (HLH) is a rare condition of immune dysregulation characterized by severe organ damage induced by an increased inflammatory response and uncontrolled T-cell and macrophage activation. In this case report, we examine a rare presentation of leukemic myocarditis in the presence of HLH, which displays an uncommon cause of an inflammatory state with several complicated concomitant diagnoses. Our patient developed severe multiorgan dysfunction involving liver and kidney failure that required prolonged critical care support, and the patient expired due to his multiorgan failure. We highlight the unusual clinical presentation of myocarditis in the setting of HLH and AML in this complicated pediatric patient and aim to improve outcomes of patients presenting similarly in the future.