Disease, Raynaud: A condition resulting in skin discoloration of the fingers and/or toes when a person is exposed to changes in temperature (cold or hot) or to emotional events. This condition can occur alone or as a part of another disease (such as rheumatoid arthritis). When the condition occurs alone it is referred to as "Raynaud disease" or primary Raynaud phenomenon. When it accompanies other diseases (such as rheumatoid arthritis), it is called secondary Raynaud 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, then turn blue because of prolonged lack of oxygen and finally, the blood vessels reopen, causing a local "flushing" phenomenon, which turns the digits red. This three-phase color sequence (white to blue to red), most often upon exposure to cold temperature, is characteristic of Raynaud disease.

The disease is named for the French physician Maurice Raynaud (1834-1881).