Case Report: Longitudinal mass cytometry profiling of a patient with disseminated histoplasmosis and secondary hemophagocytic lymphohistiocytosis.

Disseminated histoplasmosis (DH) is a rare but serious systemic fungal infection that can trigger secondary hemophagocytic lymphohistiocytosis (HLH), a hyperinflammatory syndrome with high mortality. However, the immunopathogenesis of DH-associated HLH remains poorly defined due to the lack of high-resolution immune profiling data. The dynamics of immunological and metabolic analysis was performed in a 14-year-old female patient with DH-HLH using mass cytometry (CyTOF) and multiplex cytokine profiling. Peripheral blood mononuclear cells and plasma were collected at three timepoints: before antifungal treatment, and at 1, and 2 weeks post-treatment, respectively. Immune subsets, functional markers, and cytokine/chemokine levels were evaluated. Mass cytometry identified 13 distinct immune cell subsets, including NK cells, double-negative T (DNT) cells, memory CD8+ T cells, and M2 macrophages. Longitudinal analysis demonstrated a progressive decline in proinflammatory cytokines (such as IL-6, TNF-α, and IP-10) accompanied by an expansion of reparative subsets, particularly M2 macrophages. Concurrent immune-metabolic profiling revealed a metabolic shift from glycolysis to lipid oxidation, characterized by decreased expression of GLUT1 and CPT1A and increased expression of CD36. This transition from a glycolysis-driven inflammatory state to an oxidative, immunoregulatory phenotype correlated with clinical recovery and attenuation of the cytokine storm. This case demonstrates the utility of mass cytometry for dynamic immune monitoring in infection-triggered HLH. The findings highlight metabolic reprogramming and immune restoration as key features of disease resolution and suggest potential immunometabolic targets for future diagnostic and therapeutic strategies.