Cyanosis is the medical term for a bluish color of the skin and the mucous membranes due to an insufficient level of oxygen in the blood. For example, the lips and fingernails may show cyanosis. Cyanosis can be evident at birth due to the presence of 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 and often accompanies conditions in which lung function is compromised (resulting in an inability to fully oxygenate the blood) or conditions in which the heart's pumping function is compromised. The presence of abnormal forms of hemoglobin or other abnormalities of the blood cells can also sometimes cause cyanosis. The medical term for lowered oxygen levels is hypoxia; the term anoxia refers to the absence of oxygen.
Pseudocyanosis is the appearance of cyanosis that is not associated with reduced oxygen delivery to tissues. Most causes are related to the ingestion of metals (such as silver or lead) or drugs/toxins.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.
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