Chronic mountain sickness

Chronic Mountain Sickness (CMS), also known as Monge's disease, is a medical condition that affects individuals living at high altitudes, typically above 2,500 meters (8,200 feet), for prolonged periods. It is characterized by an excessive production of red blood cells (polycythemia), leading to an abnormally high hematocrit level, which can cause the blood to become thick and sluggish. This adaptation mechanism, while initially beneficial for oxygen transport in low-oxygen environments, can eventually lead to complications such as heart failure, pulmonary hypertension, and stroke.

Symptoms and Signs

The symptoms of CMS are diverse and can significantly impact the quality of life. They include, but are not limited to:

• Headaches
• Dizziness
• Fatigue
• Breathlessness
• Palpitations
• Sleep disturbances, including central sleep apnea
• Cyanosis (bluish discoloration of the skin due to poor oxygenation)
• Venous dilation
• Tinnitus (ringing in the ears)

Causes

The primary cause of CMS is prolonged exposure to high altitude, which leads to hypoxia (low oxygen levels in the blood). In response, the body increases the production of erythropoietin, a hormone that stimulates the production of red blood cells, leading to polycythemia. While this is an adaptive response to improve oxygen delivery to tissues, excessive red blood cell production can lead to the symptoms and complications associated with CMS.

Diagnosis

Diagnosis of CMS involves a combination of clinical assessment and laboratory tests. Key diagnostic criteria include:

• Living at an altitude above 2,500 meters for a prolonged period
• Symptoms consistent with CMS
• Elevated hematocrit levels (>65% in men, >60% in women)
• Exclusion of other causes of polycythemia

Treatment

Treatment options for CMS are aimed at reducing the hematocrit level and alleviating symptoms. They include:

• Phlebotomy (removal of blood from the body) to decrease blood viscosity
• Medications such as acetazolamide to improve oxygenation and reduce erythropoietin production
• Oxygen therapy in severe cases
• In some cases, relocation to lower altitudes may be recommended

Prevention

Preventive measures for CMS focus on gradual acclimatization to high altitudes and monitoring for symptoms of the condition. Individuals moving to high altitudes should ascend slowly to allow their bodies to adjust to the lower oxygen levels.

Epidemiology

CMS is most commonly observed in populations living in the Andes, the Tibetan Plateau, and the Rocky Mountains. The prevalence of CMS increases with altitude, age, and duration of exposure to high altitudes.

See Also

• Altitude sickness
• Polycythemia
• Hypoxia (medical)
• Pulmonary hypertension

References

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