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Chronic Mountain Sickness: Etiology, Risk Factors, and Treatment

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Chronic mountain sickness is a highly prevalent progressive disabling condition caused due to prolonged hypoxia for a lifetime. Read the article to know more.

Medically reviewed by

Dr. Arpit Varshney

Published At March 31, 2023
Reviewed AtNovember 24, 2023

Introduction

Chronic Mountain sickness is an incapacitating progressive syndrome occurring in most high-altitude regions worldwide. It is caused due to lifelong exposure to hypoxia (lack of oxygen). People living above 2500 meters all over the world are at a higher risk of developing this condition. It has been found that more than 140 million people live above 2500 meters of sea level worldwide and approximately about five to ten percent of people are at a greater risk of acquiring this disease.

Chronic mountain sickness is characterized by severe symptomatic excessive erythrocytosis (higher than normal red blood cells in the blood) and increased hypoxemia (lower levels of oxygen levels in the blood), which are commonly related to pulmonary hypertension (pressure in the blood vessels supplying the lungs is very high). In more advanced cases, the condition may progress to cor pulmonale (a condition in which the right side of the heart fails) and congestive heart failure.

What Is the Etiology of Chronic Mountain Sickness?

Chronic exposure to lower levels of blood oxygen (hypoxia) is widely suggested as the main underlying cause of chronic mountain sickness. The loss of ventilatory acclimatization (the process whereby the rate of breathing increases at high altitude)to altitude hypoxia that causes central hypoventilation (inadequate breathing during sleep) has been suggested as the principal mechanism responsible for causing prolonged hypoxemia and the subsequent excessive erythrocytosis.

Evidence also suggests a genetic basis for chronic mountain fever. A single-nucleotide polymorphism in the SENP1 (sentrin-specific protease 1) gene has recently been discovered to be responsible for encoding a protease that regulates erythropoiesis.

What Are the Risk Factors Associated With Chronic Mountain Sickness?

A medical history of chronic mountain sickness along with the history of loss of ventilatory acclimatization, lack of respiratory sensitivity to reduced blood oxygen levels, sleep apnea (sleep disorder where breathing stops and starts repeatedly), and all hypopnea (reduction in ventilation), aggravated hypoxemia, older age group, male gender, post-menopausal women, and obesity are all predisposing and risk factors for chronic mountain sickness.

What Is the Epidemiology of Chronic Mountain Sickness?

It is believed that native Tibetans and Ethiopians are the most adapted ethnic groups that are most frequently affected by the disorder when compared with Andeans and Han immigrants. Men are more commonly affected than females. The disease is more prevalent in advanced age and postmenopausal women. Usually, inhabitants living above 2500 meters of sea level are at a higher risk of developing this condition.

What Are the Clinical Signs and Symptoms of Chronic Mountain Sickness?

The following clinical signs and symptoms can be seen:

  • Excessive erythrocytosis (increased red blood cell count) where the hemoglobin becomes more than 19 grams per deciliter for women and more than 21 grams per deciliter for men. Ideally, the hemoglobin for women should be 11.6 to 15 grams per deciliter, and for men, it should be between 13.2 to 16.6 grams per deciliter.

  • Hypervolemia (a condition where excessive fluid volume is present in the body).

  • Generalized dilatation of blood vessels.

  • Typical clubbing of fingers and toes.

  • Mucous membranes of the mouth and throat exhibit deep cyanosis (skin starts showing blue discoloration in individuals whose blood has very low oxygen levels).

  • Watery eyes.

  • Conjunctival hyperemia with profound capillary distensions (a pathological response of the blood vessels in response to inflammation due to infectious and non-infectious causes).

  • Dilated retinal vessels.

  • Severe bone and joint pain.

  • Decreased stamina for exercise.

  • Dyspnea (lack of breathing).

  • Insomnia (lack of sleep).

  • Headache.

  • Dizziness.

  • Mental confusion.

  • Paresthesias (prickling sensation in the hands and feet).

  • Hypertension.

  • Congestive heart failure.

How Is the Diagnosis of Chronic Mountain Sickness Made?

Firstly the causes of chronic pulmonary diseases are discarded because they can also cause hypoxemia. Once these causes have been ruled out, diagnosis of primary chronic mountain sickness is based on the presence of clinical symptoms, including dizziness, breathlessness, insomnia, tiredness, bluish discoloration of the skin, prickling in the hands and feet, dilatation of veins, muscle, and joint pain, loss of appetite, unable to concentrate, and memory loss.

Clinical signs include severe hypoxemia and pulmonary hypertension. Lung function tests should be carried out to assess normal respiratory functions.

What Is the Treatment of Chronic Mountain Sickness?

  • Non-Pharmacological Treatment - The clinical signs and symptoms of chronic mountain sickness gradually disappear after coming to lower altitudes or sea levels, and they will reappear after returning to a high altitude. Although this is an effective practice in managing the syndrome, it is a temporary solution unless the patient permanently shifts and moves to a lower-altitude site or location. It has been suggested that periodic travels to lower altitudes prevent hemoglobin levels from reaching excessive levels. Phlebotomy (surgical puncture of a vein in order to withdraw blood) is another medical practice that is performed frequently to reduce red blood cell mass and hemoglobin concentration. Mild and moderate physical exercise has been suggested as a noninvasive practical alternative therapy to improve hypoxemia and decrease excessive erythrocytosis. Periodic health check-ups are necessary for up to one year to check hemoglobin concentration and related comorbidities.

  • Pharmacological Treatment - Several drugs have shown promising results. Among these, ACE (angiotensin-converting enzyme) inhibitors, dopaminergic antagonists, and ventilatory stimulants such as medroxyprogesterone have been found to be effective in reducing hypoventilation. Pharmacological treatment with Acetazolamide (250 milligrams per day) is safely recommended for up to six months. Advanced disease cases should permanently shift to a lower altitude or sea level.

Conclusion

Millions of people all over the world live at higher altitudes. Many of these people are at a greater risk of chronic mountain sickness. It is a progressive incapacitating syndrome that is caused by prolonged exposure to severe hypoxia, often resulting in pulmonary hypertension. However, there are several risk factors that may trigger the condition. It is important to identify the clinical signs and symptoms of the syndrome to establish the diagnosis and promptly enable treatment. It is advisable to permanently shift to a lower altitude in order to improve the health condition.

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Dr. Arpit Varshney
Dr. Arpit Varshney

General Medicine

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