Raynaud phenomenon

**Definition:** Raynaud phenomenon describes an exaggerated vascular response to cold temperature or emotional stimuli resulting in episodic digital ischaemia. It is characterised by paroxysmal vasoconstriction producing initially pallor, an essential component for the diagnosis, followed by cyanosis and erythema. Primary Raynaud disease is an isolated innocuous disorder. Secondary Raynaud phenomenon occurs in association with a wide range of different disorders including dysproteinaemias and non-organ-specific systemic autoimmune diseases.