What is the most likely cause of a 25-year-old woman's shortness of breath and hemoptysis (blood-tinged sputum) at high altitude, with a history of similar episodes, normal physical exam, hypertension (134/72 mmHg), and tachycardia (heart rate 114 bpm)?

High-Altitude Pulmonary Edema (HAPE)

The most likely diagnosis is high-altitude pulmonary edema (HAPE), a life-threatening condition that requires immediate descent or oxygen therapy. 1

Clinical Presentation Matches HAPE

This patient's presentation is classic for HAPE:

• Hemoptysis (blood-tinged sputum) is a hallmark sign of advanced HAPE, occurring when protein- and red blood cell-rich fluid accumulates in the alveoli 1
• Shortness of breath and dyspnea at minimal exertion are cardinal symptoms 1
• Tachycardia (heart rate 114) reflects compensatory cardiovascular response to hypoxemia and elevated pulmonary artery pressures 2
• History of similar episodes on prior high-altitude expeditions indicates individual susceptibility, the most important risk factor for HAPE 1
• Normal physical exam early in the course is typical, as auscultatory findings may lag behind symptoms 1

Why HAPE is the Priority Diagnosis

HAPE is the leading cause of death from altitude illness, making it more immediately life-threatening than acute mountain sickness 3. The American College of Sports Medicine emphasizes that while acute mountain sickness affects over 50% of individuals above 4,500 meters, HAPE represents a more severe and potentially fatal complication 4.

The pathophysiology involves:

• Excessively elevated pulmonary artery pressures (mean 35-55 mmHg) that precede pulmonary edema development 1
• Elevated pulmonary capillary pressure with protein-rich, hemorrhagic edema fluid without inflammatory markers 1
• Decreased alveolar fluid clearance contributing to non-cardiogenic pulmonary edema 1

Immediate Management Algorithm

Descent is mandatory and takes absolute priority 3:

1. Immediate descent to lower altitude - this is the definitive treatment 1, 3
2. Supplemental oxygen if descent is delayed or impossible 1
3. Nifedipine can be used as adjunctive therapy until descent is possible 1

Key Differentiating Features

While altitude-induced cough affects 40-60% of mountaineers 5, this patient's hemoptysis distinguishes HAPE from simple high-altitude cough syndrome. The blood-tinged sputum specifically indicates alveolar hemorrhage from elevated pulmonary capillary pressures 1.

Recurrence risk is approximately 60% in susceptible individuals who ascend rapidly above 4,500 meters 4, making this patient's history of prior episodes particularly concerning.

Prevention for Future Expeditions

For this susceptible individual:

• Slow ascent with average altitude gain not exceeding 400 meters/day above 2,500 meters 1
• Prophylactic nifedipine if progressive acclimatization is not possible 1
• Consider avoiding rapid ascents entirely given documented susceptibility 4