The hemophagocytic lymphohistiocytosis (HLH) syndrome is a hyperimmune disorder characterized by lymphohistiocytic infiltrations, elevated cytokine levels in the blood, macrophage activation, and hemophagocytosis, frequently presenting with a febrile septic picture. This unusual disease is more common in infancy and childhood than adulthood. It is classified as primary or familial when a genetic defect is identified and secondary or acquired when triggered by certain infections, autoimmune disorders, or malignancies. If or when such patients expire, they typically do so within a hospital or under a physician's care and so such cases rarely come to the attention of forensic pathologists. We report on the unexpected deaths of two hospitalized adult cases of HLH brought to autopsy without a premortem diagnosis. Postmortem examination demonstrated marked hepatosplenomegaly and lymphadenopathy in association with hemophagocytosis. Although very uncommon HLH must be considered in infants, children, or adults who die unexpectedly with an undiagnosed septic presentation.