A 28-year-old man develops headache, nausea, cough, shortness of breath, and fatigue while hiking the Mount Whitney Summit Trail in California. The patient arrived 3 days ago from Los Angeles. He is also accompanied by his friend who came from New Jersey, but his friend does not have any symptoms. The patient has no medical conditions and takes no medications. He drinks 3 or 4 beers every day. Temperature is 38.3 C (101 F), blood pressure is 130/90 mm Hg, pulse is 120/min, and oxygen saturation is 85% on ambient air. Examination shows cyanosis, dry mucous membranes, and bilateral crackles. Chest x-ray reveals diffuse, patchy infiltrates and normal heart size. Laboratory studies reveal leukocytes of 14,000/mm³ with 74% neutrophils. Serum procalcitonin level is 0.10 mcg/L (normal:

Question

A 28-year-old man develops headache, nausea, cough, shortness of breath, and fatigue while hiking the Mount Whitney Summit Trail in California. The patient arrived 3 days ago from Los Angeles. He is also accompanied by his friend who came from New Jersey, but his friend does not have any symptoms. The patient has no medical conditions and takes no medications. He drinks 3 or 4 beers every day. Temperature is 38.3 C (101 F), blood pressure is 130/90 mm Hg, pulse is 120/min, and oxygen saturation is 85% on ambient air. Examination shows cyanosis, dry mucous membranes, and bilateral crackles. Chest x-ray reveals diffuse, patchy infiltrates and normal heart size. Laboratory studies reveal leukocytes of 14,000/mm³ with 74% neutrophils. Serum procalcitonin level is 0.10 mcg/L (normal: <0.25). What is the most likely diagnosis in this patient?

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Explanation: 11ec25c8_d1fb_3180_bc81_e912fa6e303b_MD0003_00 This patient with shortness of breath, fatigue, headache, and nausea within several days of arriving at high elevation (ie, >2500 m) likely has high-altitude illness (HAI). Alcohol intake suppresses central respiratory drive and can worsen HAI. The patient's cough, greater-than-expected hypoxemia, and patchy infiltrates on chest x-ray suggest a further complication of HAI, high-altitude pulmonary edema (HAPE). hypoxemia In response to the low partial pressure of inspired oxygen (PiO₂) at high altitude, the lungs undergo hypoxic vasoconstriction to optimize alveolar-capillary gas exchange. Some individuals have a genetic predisposition to developing HAPE because they experience unevenly distributed hypoxic vasoconstriction, which exposes the pulmonary capillaries in relatively less vasoconstricted areas to high perfusion pressure. This causes regional disruption of the alveolar-capillary membrane and leads to characteristic patchy, bilateral pulmonary edema (noncardiogenic pulmonary edema). ₂ bilateral pulmonary edema The differentiation of HAPE from bacterial pneumonia (Choices B and E) can be challenging as both conditions can cause fever, leukocytosis, hypoxemia, and bilateral lung infiltrates. Recent ascent to high altitude suggests HAPE; conversely, an extended stay at high altitude prior to symptom onset rules out HAPE as it almost never occurs after >1 week at the same altitude. Mild leukocytosis is common with HAPE, but leukocytes >15,000/mm³ or the presence of bands suggests bacterial pneumonia. Serum procalcitonin is typically elevated only with bacterial infection, and normal procalcitonin level suggests HAPE. Rapid improvement of hypoxemia with supplemental oxygen is highly suggestive of HAPE. Although hypoxemia due to multifocal pneumonia does not quickly improve with supplemental oxygen (due to widespread intrapulmonary shunting), supplemental oxygen alleviates the hypoxic vasoconstriction in HAPE to reduce alveolar-capillary perfusion pressure and rapidly improve the edema and hypoxemia. (Choices A and C) Although Chagas disease more typically causes chronic heart failure due to dilated cardiomyopathy, acute disease may rarely cause myocarditis with acute-onset heart failure and pulmonary edema. However, this and other causes of cardiogenic pulmonary edema (eg, left ventricular diastolic dysfunction) involve volume overload and the transmission of elevated left atrial pressure back to the pulmonary veins and capillaries. Dry mucous membranes rule out significant volume overload, and normal heart size on chest x-ray makes heart failure less likely. Educational objective: High-altitude pulmonary edema (HAPE) typically presents with shortness of breath, cough, hypoxemia, and bilateral lung infiltrates. Characteristics that favor HAPE over multifocal pneumonia include recent ascent to high altitude, normal procalcitonin with no more than mild leukocytosis, and rapid improvement of hypoxemia with supplemental oxygen. References: Update on high-altitude pulmonary edema: pathogenesis, prevention, and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/19099331)

A 28-Year-Old Man Develops Headache, Nausea, Cough, Shortness of Breath