The prevalence of High Altitude Polycythemia (or Chronic Mountain Sickness) is between 8 and 15% in the high altitude regions of South America. There is no pharmacological treatment available. After a first preliminary study in 2003 demonstrating the beneficial effects of acetazolamide in reducing hematocrit in these patients, after 3 weeks of treatment, we want to confirm this effect and implement a treatment protocol of 3 month-duration.

Chronic mountain sickness (CMS) is characterized by an excessive number of red cells in the blood of persons living permanently above the altitude of 2,500m. The symptoms of this very incapacitating disease are : headaches, chronic asthenia, digestive troubles, sleep disturbances. The hemoglobin concentration is higher than 21 g/dl of blood. In addition, patients show a pulmonary hypertension of variable degree, as well as a systemic hypertension.

This disease affects essentially males, but women are also concerned after menopause. The evolution of the disease is always very dramatic, towards a cardiac failure and cerebral vascular stroke. The prevalence is between 8% and 15% on the Andean Altiplano . No pharmacological treatment is available.

A preliminary study was performed (Richalet et al. AJRCCM, 2005) that demonstrated the efficiency of acetazolamide (a carbonic anhydrase inhibitor) in reducing the hematocrit and the erythropoetin concentration,and increasing nocturnal oxygen saturation in patients suffering from CMS, after 3 weeks of treatment.

We plan to perform a double-blinded placebo-controlled study to evaluate the efficiency of a 3-month treatment with daily 250 mg acetazolamide to reduce the hematocrit and hemoglobin concentrations and ameliorate the clinical symptoms of 55 patients suffering from CMS and living at high altitude (Cerro de Pasco, Peru).

Inclusion Criteria:

• patients with Chronic mountain sickness and Hb > 21g/dl

Exclusion Criteria:

• patients smokers
• patients with respiratory or cardiovascular or renal disease