[Raynaud phenomenon in dermatology. Part 1: Pathophysiology and diagnostic approach].
Raynaud phenomenon (RP) is characterized by recurrent spasms of small digital arterioles/arteries at fingers and toes, usually triggered by cold and emotional stress. Clinically a sudden pallor of individual digits is followed by reactive hyperemia, in severe cases also by cyanosis. One distinguishes between primary RP, i.e. RP without an underlying disease or drug intake, and secondary RP, which is causally related to an underlying disease or to intake of certain drugs (e.g. interferon, cisplatin). Primary RP is frequent (prevalence of about 13-20% in northern or central Europe), while secondary RP is rare, but the major presenting symptom for systemic sclerosis (SSc). Differential diagnosis includes cold-induced pallor, acute embolic events, paroxysmal hematoma of the finger or erythromelalgia. Vasoconstrictive mechanisms outweigh vasodilatory ones in endothelial cells and vascular smooth muscle. Although soluble mediators such as endothelin or certain prostaglandins have been exploited successfully for therapy, the extent of their involvement in the initial pathophysiology of RP is unclear. Secondary RP (associated with SSc) additionally features morphological alterations with compromise of the vessel lumen. As RP can result in severe discomfort and complications, timely diagnosis and treatment is essential.