HIF1A and ablepharon macrostomia syndrome: Currently, the mechanism of VEGF expression in the pathogenesis of AMS is understood as follows: HIF-1a initiates VEGF transcription under hypoxia and makes VEGF RNA more stable and hypoxia increases VEGF RNA and adenosine levels, and high VEGF contents in patients with AMS at high altitudes are correlated with the severity of the syndrome.[29,30] These results suggest that VEGF is an important pathogenic factor of AMS.