Fueling the FIRES: Hemophagocytic lymphohistiocytosis in febrile infection‐related epilepsy syndrome

OBJECTIVES: Although secondary hemophagocytic lymphohistiocytosis (HLH) has been reported in children with critical illness of various etiologies, it has not been reported in patients with febrile infection-related epilepsy syndrome (FIRES). We describe a series of patients with concurrent HLH and FIRES in an effort to establish common pathophysiologic abnormalities. METHODS: Five patients with FIRES who were assessed for HLH were identified from a neurocritical care database. All were previously healthy and had extensive diagnostic testing. All had clinical deterioration with multiorgan dysfunction prompting HLH screening 20-29 days after hospitalization. Markers for inflammatory dysregulation were assessed in cerebrospinal fluid (CSF) and serum at various time points. Outcomes were assessed 6 months after presentation. RESULTS: Three patients met clinical criteria for secondary HLH. Elevation of specific cytokines/chemokines was variable. CSF neopterin, high mobility group box 1 (HMGB1), and C-X-C motif chemokine ligand 8 (CXCL8) were significantly elevated in all. Interleukin-1β (IL-1β) and IL-18 were not elevated in any of the samples. Treatment and outcomes were variable. SIGNIFICANCE: We describe 3 patients with HLH and FIRES. The co-occurrence of these 2 rare disorders suggests the possibility of a common immune dysregulation phenotype prolonging epileptogenesis. HLH screening in critically ill patients with FIRES may yield a broader understanding of shared inflammatory processes.