Introduction: Acute mountain sickness, high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE) are a spectrum of high-altitude conditions, with HACE being the most life-threatening. Most cases develop at altitudes of greater than 4,000 meters (~13,000 feet) above sea level and after one to five days.

Case Report: A previously healthy 46-year-old female presented to the emergency department with ataxia, altered mental status, and vomiting that developed after rapidly ascending to ~2,400 meters (~7,800 feet) above sea level. She was treated for HACE and HAPE with resolution of her symptoms within 24 hours.

Conclusion: High-altitude pulmonary edema and HACE can develop rapidly and at moderate altitudes. Expeditious recognition and treatment is imperative to avoid life-threatening complications.