Chronic mountain sickness
Background
- Excessive polycythemia at altitude (Hgb >20 g/dL in men, >19 in women)
- Occurs in long-term high-altitude residents (typically >3,000m) who develop loss of ventilatory acclimatization
- Risk factors: COPD, obstructive sleep apnea, impaired respiratory drive, obesity, advancing age
- Also known as Monge disease
Clinical Features
- Headache, dizziness, difficulty concentrating
- Drowsiness, exercise intolerance
- Impaired peripheral circulation: cyanosis, digital clubbing
- Paresthesias
- Pulmonary hypertension may develop
Differential Diagnosis
High Altitude Illnesses
- Acute mountain sickness
- Chronic mountain sickness
- High altitude cerebral edema
- High altitude pulmonary edema
- High altitude peripheral edema
- High altitude retinopathy
- High altitude pharyngitis and bronchitis
- Ultraviolet keratitis
Evaluation
- CBC: markedly elevated hematocrit/hemoglobin
- Pulse oximetry: low SpO2 at altitude (lower than expected)
- ABG: chronic respiratory alkalosis with metabolic compensation
- Echocardiography if concern for pulmonary hypertension
Management
- Definitive: Descent to lower altitude (curative)
- Phlebotomy for symptomatic relief (target Hgb <18)
- Supplemental oxygen, especially during sleep
- Acetazolamide 250 mg BID may improve ventilatory drive
- Treat contributing conditions (CPAP for OSA, bronchodilators for COPD)
Disposition
- Outpatient management in most cases with referral to primary care
- Recommend relocation to lower altitude for definitive treatment