Leptospira/Salmonella Bacterial Coinfection as a Trigger of Secondary Hemophagocytic Lymphohistiocytosis

Carlos DMJ, Carmen VCG, Liliam CC and Argencio AN

Published on: 2026-01-09

Abstract

Secondary hemophagocytic lymphohistiocytosis (HLH) triggered by bacterial infections is a rare entity in pediatrics. It is characterized by a hyperinflammatory state in which the implicated pathogen induces a cytotoxic immune response mediated by Th1 lymphocytes, activating natural killer (NK) cells and macrophages that release cytokines responsible for the hyperinflammatory cascade. The clinical presentation includes fever, organomegaly, cytopenias, elevated acute-phase reactants, and the demonstration of hemophagocytosis in bone marrow, spleen, lymph nodes, or liver. We report the case of a 14-year-old adolescent with bacterial coinfection caused by Leptospira spp. and Salmonella, an infrequent association that increases diagnostic complexity. Early recognition and timely initiation of treatment prevented severe complications and mortality.