Raynaud's disease: A condition that results in discoloration of the skin on the fingers and/or toes when a person is exposed to changes in temperature or to emotional events. Raynaud's disease, also known as primary Raynaud's phenomenon, can accompany other diseases; when it does, it is called Raynaud's phenomenon or secondary Raynaud's phenomenon. The skin discoloration occurs because an abnormal spasm of the blood vessels causes a diminished blood supply. Initially, the digits involved turn white because of diminished blood supply, and then they turn blue because of prolonged lack of oxygen. Finally, the blood vessels reopen, causing flushing that turns the digits red.