High-Altitude Pulmonary Edema (HAPE) is a serious condition that can occur when individuals ascend to high altitudes, typically above 8,000 feet (2,400 meters). It is caused by a lack of oxygen, leading to fluid accumulation in the lungs. Symptoms include shortness of breath, cough, fatigue, and chest tightness, which can worsen if not treated promptly. HAPE is more common in individuals who ascend rapidly without proper acclimatization. Treatment involves descending to a lower altitude and administering supplemental oxygen. In severe cases, medications like diuretics may be used to help reduce fluid buildup in the lungs.