Quincke's sign

Quincke's sign is a visible pulsation of the fingernail bed or cuticle when pressure is applied to an arm or finger. It indicates a significant decrease in peripheral resistance, often due to severe aortic regurgitation, allowing increased blood flow into the vessels. When small artery capillaries beneath the nail bed are pressurized, the pulsating blood flow can be seen as a turbulent, alternating color change—red and pale—reflecting the heartbeat. This sign helps clinicians identify underlying cardiovascular issues that cause abnormal blood flow and pressure changes in the peripheral vessels.