Fatal Hemophagocytic Lymphohistiocytosis Triggered by Incompletely Treated Brucellosis: A Case Report and Warning from an Endemic Region

Background: Brucellosis, a common zoonosis in endemic areas, can rarely precipitate the life-threatening hyperinflammatory syndrome, hemophagocytic lymphohistiocytosis (HLH). This complication carries a high mortality rate, especially when diagnosis and treatment are delayed. Case Presentation: A 75-year-old male farmer from a brucellosis-endemic region in Iran presented with hematochezia, fever, weight loss, and pancytopenia. He had been diagnosed with active brucellosis 40 days prior but discontinued antibiotic therapy after four weeks. During hospitalization, he developed progressive cytopenias, hyperferritinemia (6,022 ng/mL), hypertriglyceridemia, and splenomegaly. A bone marrow biopsy confirmed hemophagocytosis, leading to a diagnosis of secondary HLH. Despite initiating treatment per HLH-2004 protocols with corticosteroids, etoposide, and intravenous immunoglobulin, his condition deteriorated rapidly. He developed altered mental status, required intubation, and succumbed to the illness. Conclusion: This case underscores brucellosis as a potential trigger for HLH. It highlights the critical importance of ensuring complete treatment for brucellosis and maintaining a high index of suspicion for HLH in patients with persistent fever, cytopenias, and hepatosplenomegaly, even in the context of a known infection. Early, aggressive immunomodulatory therapy alongside appropriate antimicrobials is essential, though outcomes can remain poor, particularly in elderly patients.