The Raynaud phenomenon (RP) is an exaggerated vascular response to cold temperature or emotional stress. The phenomenon is manifested clinically by sharply demarcated color changes of the skin of the digits. Abnormal vasoconstriction of digital arteries and cutaneous arterioles due to a local defect in normal vascular responses is thought to underlie the disorder.
RP is considered primary if these symptoms occur alone without evidence of any associated disorder. By comparison, secondary RP refers to the presence of the disorder in association with a related illness, such as systemic lupus erythematosus and systemic sclerosis (SSc; scleroderma).