• A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• A clinical finding in which the skin is noted to have a bluish cast due to an increased concentration of deoxyhemoglobin in cutaneous blood vessels on visual inspection.
  ACC/AHA Clinical Data Terminology
  American College of Cardiology and American Heart Association , 2020
• A condition in which skin turns blue due to a lack of oxygen in the blood, often because of heart failure or lung disease.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• Blue-colored skin caused by too little oxygen in the blood.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• Blueness of the skin caused by excessive amounts of deoxyhemoglobin in the skin vessels.
  CRISP Thesaurus
  National Institutes of Health, 2006
• Bluish discoloration of the skin and mucosa due to poor circulation or inadequate oxygenation of arterial or capillary blood.
  Human Phenotype Ontology (HPO)
  The Human Phenotype Ontology Project, 2021
• A disorder characterized by a bluish discoloration of the skin and/or mucous membranes.
  Common Terminology Criteria for Adverse Events
  U.S. National Institutes of Health, 2021
• Cyanosis is a bluish discoloration of the skin resulting from an inadequate amount of oxygen in the blood. Cyanosis occurs when oxygen-depleted (deoxygenated) blood, which is bluish rather than red, circulates through the skin. Cyanosis can be caused by many types of severe lung or heart disease that cause levels of oxygen in the blood...
  Merck Manuals
  Merck & Co., Inc., 2020
• Cyanosis is a bluish or purplish tinge to the skin and mucous membranes. See the images below.
  Medscape
  WebMD, 2019