Crimean-Congo Hemorrhagic Fever in Children: Secondary Hemophagocytic Lymphohistiocytosis and Time-course of Biomarkers in a Single-Center Cohort (2019-25).

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral infection that may present mildly in children but can progress to severe clinical states due to secondary hemophagocytic lymphohistiocytosis (HLH). We retrospectively analyzed the clinical, laboratory, and treatment data of children aged 0-18 years with polymerase chain reaction (PCR)-confirmed CCHF who were hospitalized at Hacettepe University, a large referral center for CCHF, between January 2019 and July 2025. Serial laboratory values (Days 0, 3, 7, and 10) and therapeutic interventions were evaluated. Twenty-two children (median age 13 years, 72% male) were included. The most frequent symptoms were fever (100%), bradycardia (59%), and conjunctival hyperemia (41%). HLH was diagnosed in 18 patients (82%). Ribavirin (91%), intravenous immunoglobulin (IVIG) (86%), and corticosteroids (68%) were administered. Platelet counts began to recover by Day 7, whereas ferritin declined gradually and normalized later. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels showed a progressive decrease. No patient required intensive care, and none died. Secondary HLH was highly prevalent among pediatric CCHF cases, yet outcomes were favorable with early antiviral and immunomodulatory therapy. Platelet recovery and delayed ferritin normalization may serve as practical biomarkers of disease resolution. Prospective multicenter studies with cytokine and viral-load profiling are warranted.