High‑altitude polycythemia: Unveiling the molecular landscape beyond erythropoietin (Review)

High‑altitude polycythemia (HAP) is classically attributed to erythropoietin (EPO)‑driven erythrocytosis, yet epidemiological and mechanistic evidence increasingly challenges this monocular view. Field data have demonstrated that up to 40% of individuals with a hematocrit level >68% circulate EPO within the sea‑level reference range, whereas multi‑omics studies have revealed sustained HIF activity, mitochondrial oxidative stress, iron dysregulation, gut dysbiosis and epigenetic reprogramming as parallel, EPO‑independent drivers. Hypoxia‑inducible microRNAs, hepcidin suppression, TLR4‑IL‑6 signaling and defective mitophagy converge to lock erythroid precursors into a survival‑plus‑proliferation state even after ambient oxygen levels normalize. The purpose of the present review is to integrate these disparate pathways into a unified molecular framework and to outline a phased, biomarker‑guided therapeutic roadmap for the precise prevention of maladaptive polycythemia at high altitudes.