Experimental Factor Ontology identifier EFO_0010143 (chronic mountain sickness) is a pathological condition resulting from chronic exposure to hypoxia at high altitude. The syndrome is characterized by an excessive number of red blood cells associated with a high blood hemoglobin concentration ([Hb]), hypoxemia, and, in some cases, pulmonary hypertension. Clinical signs include headache, fatigue, sleep disturbances, dyspnea, digestive complaints, and high risk of thrombotic events. Also known as: Monge's disease.