What is Erythromelalgia
Erythromelalgia is a rare, debilitating neurovascular pain disorder characterized by episodic burning pain accompanied by red, hot extremities (primarily feet and hands), with symptoms triggered by heat or exercise and relieved by cooling. 1
Clinical Presentation
The disorder presents with a characteristic triad:
- Intense burning pain in the distal extremities
- Erythema (redness) of affected areas
- Increased warmth and sometimes swelling of the extremities
Episodes are typically triggered by:
- Physical activity or exercise
- Exposure to warm temperatures
- Heat exposure
- Stress
Patients characteristically seek relief through cooling measures, though this can lead to complications if done excessively (ice water immersion can cause tissue damage and ulcerations). 1
Pathophysiology
The underlying mechanism involves vasodilation of thermoregulatory arteriovenous anastomoses, likely representing a dysregulation of endogenous temperature control. 1 Recent pathology studies suggest this is a dysautonomia syndrome with vascular ectasia and denervation of eccrine coils and arteries, similar to small fiber neuropathy. 2
Classification
Primary (Inherited) Erythromelalgia
Approximately 5% of patients have a family history with autosomal dominant inheritance. 1 This form is caused by gain-of-function mutations in the SCN9A gene, which encodes Nav1.7 sodium channels in nociceptive sensory neurons. 1 These mutations cause sodium channels to open more easily and remain open longer, resulting in prolonged neuronal activation and explaining the disproportionate pain experienced during episodes. 1
Secondary Erythromelalgia
Associated with underlying conditions, most notably:
- Myeloproliferative diseases (essential thrombocythemia, polycythemia vera) - approximately 5% of cases 1
- Autoimmune conditions 2
- Certain medications and toxins 3
Idiopathic Erythromelalgia
No identifiable cause or family history. 1
Important note: The distinction between primary and secondary forms does not substantially affect management. 1
Diagnostic Challenges
The diagnosis is frequently missed because symptoms are intermittent and extremities may appear completely normal during clinical examination. 1 Patients often self-diagnose before seeking medical attention. The diagnosis is primarily clinical, though genetic testing for SCN9A mutations can confirm primary forms when present (detected in only 19% of cases in recent studies). 4
Key differential diagnoses to exclude:
- Complex regional pain syndrome
- Cellulitis
- Non-freezing cold injury
- Small fiber neuropathies 3
Clinical Significance and Prognosis
This is not merely a quality-of-life issue - patients with erythromelalgia have significantly increased morbidity, mortality, and suicide risk compared to the general population. 1 The pain can be so severe that it fundamentally alters lifestyle, with patients avoiding normal activities and engaging in extreme cooling behaviors that can cause additional tissue damage. 1
Common Pitfalls
- Missing the diagnosis due to normal examination between episodes - maintain high clinical suspicion based on history alone
- Allowing harmful cooling behaviors - patients must be counseled that ice water immersion and continuous fan use can cause immersion foot, ulcerations, and windburn-like injury 1
- Assuming all cases need genetic testing - only 19% have detectable SCN9A mutations, and testing doesn't change management 4
- Failing to screen for myeloproliferative disease - this treatable secondary cause should be evaluated in all patients 1