Polyrexia, often referred to as polycythemia, is a condition characterized by an increased number of red blood cells in the bloodstream, leading to elevated blood viscosity. This can result in complications such as hypertension, thrombosis, and increased risk of cardiovascular issues. It may be primary, due to genetic factors, or secondary, often as a response to hypoxia or other underlying conditions. Diagnosis typically involves blood tests and assessment of symptoms to determine the appropriate treatment.