Infection-associated severe bone marrow fibrosis mimicking hemophagocyticlymphohistiocytosis

Abstract Infection-associated bone marrow fibrosis is an uncommon and under-recognized manifestation of severe systemic infection and may pose a significant diagnostic challenge when accompanied by cytopenias and hyperinflammatory features. We report the case of a 31-year-old male who presented with persistent high-grade fever, hepatosplenomegaly, pancytopenia, hyperferritinemia, and raised inflammatory markers, raising clinical suspicion for hemophagocyticlymphohistiocytosis. Bone marrow examination revealed a hypocellular marrow with marked suppression of trilineage hematopoiesis and extensive intertrabecular fibrosis (MF-3 reticulin fibrosis according to the European Consensus grading system). Notably, overt intramedullary bacterial colonies were identified within the marrow spaces, while no hemophagocytosis, granulomas, or evidence of hematolymphoid malignancy was seen. Microbiological evaluation confirmed multidrug-resistant Gram-negative sepsis due to Acinetobacter calcoaceticus–baumannii complex and Pseudomonas aeruginosa . This case highlights a rare but important diagnostic pitfall in which overwhelming bacterial infection results in severe secondary bone marrow fibrosis and mimics hemophagocytic syndromes. Recognition of this entity is critical, as timely bone marrow evaluation can redirect diagnosis and management in patients with sepsis and unexplained cytopenias.