Cyanosis

Cyanosis is a term for a bluish discolouration of the skin and mucous membranes with a higher content of deoxygenated haemoglobin in the blood. This colouration is manifested when the content of non-oxygenated haemoglobin in the blood is above  50 g/l. Therefore, cyanosis is observed more often in polyglobulia than in anaemia (when the total haemoglobin content in the blood is reduced).