Cyanosis is defined as:

• A. A bluish discoloration of the skin caused by reduced hemoglobin in the blood
• B. A yellowing of the skin due to bilirubin
• C. A reddening of the skin due to inflammation
• D. A brownish discoloration caused by skin aging

Answer: (A)

Cyanosis is the bluish discoloration of the skin and mucous membranes caused by an increased amount of deoxygenated hemoglobin in the blood. When oxygen levels are low, hemoglobin remains in its reduced form and absorbs and reflects light in a way that gives the skin a blue tint, especially in areas with thin skin or less perfusion. Central cyanosis indicates systemic hypoxemia and shows up around the lips and tongue, while peripheral cyanosis results from vasoconstriction in the fingers or toes. In clinical practice, noticing cyanosis during activity prompts evaluation of oxygenation and vital signs to ensure patient safety. The other color changes described correspond to different processes (yellow from bilirubin in jaundice, red from inflammation, brown from aging) and are not caused by deoxygenated hemoglobin.