I have witnessed a Korean mountain biker who succumbed to AMS and had to be airlifted by the Nepalese Army's helicopter to the Grande Hospital for medical attention. He participated in the Yak Ru High Altitude Mountain Bike Race held in the Annapurna Mountain Range, Nepal in 2014.

He displayed most of the observable symptoms in the Moderate & Acute stages. He was lucky that a doctor with the relevant expertise was with the race support crew.

PS: This race is organised annually by Steemian @sunilcsharma.