A bluish color of the skin and the mucous membranes due to insufficient oxygen in the blood. For example, the lips may show cyanosis. Cyanosis can be evident at birth, as in a “blue baby” who has a heart malformation that permits blood that is not fully oxygenated to enter the arterial circulation. Cyanosis can also appear at any time later in life.
The word “cyanosis” comes from the Greek “cyanos” meaning dark blue.