RT Book, Section A1 Basnyat, Buddha A1 Tabin, Geoffrey A2 Jameson, J. Larry A2 Fauci, Anthony S. A2 Kasper, Dennis L. A2 Hauser, Stephen L. A2 Longo, Dan L. A2 Loscalzo, Joseph SR Print(0) ID 1155960843 T1 Altitude Illness T2 Harrison's Principles of Internal Medicine, 20e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259644016 LK accesspharmacy.mhmedical.com/content.aspx?aid=1155960843 RD 2024/10/11 AB Mountains cover one-fifth of the earth’s surface; 140 million people live permanently at altitudes ≥2500 m, and 100 million people travel to high-altitude locations each year. Skiers in the Alps or Aspen; tourists to La Paz, Ladakh, or Lahsa; religious pilgrims to Kailash-Manasarovar or Gosainkunda; trekkers and climbers to Kilimanjaro, Aconcagua, or Everest; miners working in high-altitude sites in South America; and military personnel deployed to high-altitude locations are all at risk of developing acute mountain sickness (AMS), high-altitude cerebral edema (HACE), high-altitude pulmonary edema (HAPE), and other altitude-related problems. AMS is the benign form of altitude illness, whereas HACE and HAPE are life-threatening. Altitude illness is likely to occur above 2500 m but has been documented even at 1500–2500 m. In the Mount Everest region of Nepal, ~50% of trekkers who walk to altitudes >4000 m over ≥5 days develop AMS, as do 84% of people who fly directly to 3860 m. The incidences of HACE and HAPE are much lower than that of AMS, with estimates in the range of 0.1–4%. Finally, reentry HAPE, which in the past was generally limited to highlanders (long-term residents of altitudes >2500 m) in the Americas, is now being seen in Himalayan and Tibetan highlanders—and often misdiagnosed as a viral illness—as a result of recent rapid air, train, and motorable-road access to high-altitude settlements.