Raynaud's Phenomenon
Raynaud's phenomenon is episodic digital vasospasm triggered by cold or stress, causing sharply demarcated colour change, numbness and pain. Primary disease is usually benign, but later-onset, asymmetric or tissue-damaging disease may be secondary to systemic sclerosis, another connective-tissue disorder, large-vessel disease, vibration or medicines.
Definition
Raynaud's phenomenon is episodic vasospasm of digital arteries and arterioles, usually triggered by cold or emotional stress, producing well-demarcated colour change with numbness or pain. It is primary when occurring without an underlying disease and secondary when associated with connective-tissue, vascular, occupational, drug-related or other pathology.
First principles
The colour change reflects reversible flow failure
Cold or emotional stress triggers exaggerated sympathetic vasoconstriction in the digital vessels. Pallor reflects reduced arterial flow, blue or purple colour reflects stagnant deoxygenated blood, and redness follows reperfusion. The sequence is common but not obligatory, and symptoms may be numbness, pain or tingling without all three colours.
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