Raynaud's disease, also known as Raynaud's phenomenon or Raynaud's syndrome, is a medical condition that affects the blood vessels. The condition is characterized by the narrowing of the blood vessels in the extremities, particularly the fingers and toes, in response to cold temperatures or stress. This causes a decrease in blood flow to the affected areas, leading to numbness, tingling, and discoloration of the skin. Synonyms for Raynaud's disease include digital vasospasm, acrosyndrome, and frostbite of the fingers. Other terms used to describe the condition are Raynaud's phenomenon secondary to an underlying disease, such as scleroderma, and Raynaud's phenomenon of unknown cause.