Final answer:
Cyanosis is the condition of the skin and mucous membranes that appears blue or purple due to insufficient oxygen in the blood, often a sign of serious underlying cardiovascular or respiratory issues.
Step-by-step explanation:
The condition of the skin and mucous membrane caused by oxygen deficiency is cyanosis. Cyanosis involves a blue or purple coloration of the skin, especially when active, due to a lack of sufficient oxygenated blood. Disorders such as severe septal defects like tetralogy of Fallot and patent foramen ovale can lead to cyanosis, which is also seen in emergencies where breathing is compromised.
Different skin colourations can indicate various diseases. For instance, liver issues can lead to jaundice, featuring yellow skin due to bilirubin accumulation. Addison's disease can give the skin a deep bronze color, while in conditions where there is a sudden drop in oxygenation, the skin may appear ashen and then lead to cyanosis. Unlike these conditions that alter skin color based on specific substances or lack thereof, skin pigmentation disorders like albinism and vitiligo affect appearance due to a lack of or damage to melanocytes.
It is essential to distinguish between the discolouration caused by pigmentation issues and that caused by oxygen deficiency. Belonging to the latter, cyanosis is a serious sign that requires immediate medical attention to address the underlying oxygen deprivation.