What causes Raynaud's phenomenon?

Causes of Raynaud's Phenomenon

Raynaud's phenomenon is primarily caused by vasospasm of the digital arteries, which can occur as a primary condition (primary Raynaud's) or secondary to underlying pathologies such as autoimmune disorders, particularly systemic sclerosis. 1, 2

Primary vs. Secondary Raynaud's

Primary Raynaud's (Raynaud's Disease)

Primary Raynaud's occurs without any identifiable underlying cause and involves:

• Increased activation of sympathetic nerves in response to cold or emotional stress 3
• Local vascular dysfunction rather than structural abnormalities 3
• Increased sensitivity to cold of the adrenergic receptors on digital artery vascular smooth muscle 3

Secondary Raynaud's

Secondary Raynaud's is associated with:

• Autoimmune/connective tissue diseases - particularly systemic sclerosis, systemic lupus erythematosus, and rheumatoid arthritis 4, 2
• Vascular pathologies - including atherosclerosis and thromboangiitis obliterans (Buerger's disease) 4
• Hematological disorders - such as prothrombotic diseases with abnormalities in the clotting system 4
• Medication use - ergot alkaloids, bleomycin, and clonidine can trigger vasospasm 1
• Occupational factors - vibration injury (e.g., from pneumatic tools) 1

Pathophysiological Mechanisms

The pathophysiology of Raynaud's phenomenon involves several mechanisms:

1. Vasospastic component:

   • Abnormal sympathetic nervous system activation 3
   • Impaired habituation of cardiovascular response to stress 3

2. Vascular mediators:

   • Increased levels of vasoconstrictors (endothelin, 5-hydroxytryptamine, thromboxane) 3
   • Deficiency or increased degradation of nitric oxide 3
   • Increased oxidative stress 3

3. In systemic sclerosis:

   • Progressive obliterative microangiopathy in addition to vasospasm 2
   • Structural vascular damage that compounds functional vasospasm 2

Common Triggers

Raynaud's attacks are commonly precipitated by:

• Cold exposure - the most common trigger 1, 5
• Emotional stress 1, 5
• Smoking 1
• Certain medications - particularly vasoconstrictive drugs 1, 5

Clinical Manifestations

Raynaud's phenomenon typically presents with:

• Triphasic color changes - white (ischemia), blue (deoxygenation), and red (reperfusion) 3
• Pain and/or paresthesia due to sensory nerve ischemia 3
• Digital ischemia - potentially leading to ulceration and tissue loss in severe cases, particularly with secondary Raynaud's 2

Important Considerations

• Recent research challenges the purely "episodic" nature of Raynaud's, particularly in systemic sclerosis, suggesting more persistent vascular compromise 2
• The term "primary Raynaud's" may encompass several distinct entities including functional vasospastic disorder, physiological thermoregulatory responses, subclinical atherosclerosis, and "cold intolerance" 2
• Secondary Raynaud's, particularly associated with systemic sclerosis, carries a higher risk of digital ulceration and tissue loss compared to primary Raynaud's 2

Understanding the specific cause of Raynaud's is crucial for determining appropriate management strategies and preventing complications, particularly in cases of secondary Raynaud's where the underlying condition requires targeted treatment.