Differential Diagnosis: Erythromelalgia vs. Small Fiber Neuropathy
This presentation is most consistent with erythromelalgia, a rare neurovascular disorder characterized by episodic burning pain with paradoxical temperature perception, where affected skin feels cool to touch despite the patient experiencing intense burning sensations. 1, 2, 3
Clinical Features Supporting Erythromelalgia
The combination of burning sensation under the skin and joints followed by feelings of freezing with objectively cool skin is pathognomonic for erythromelalgia, which presents with:
- Intense burning pain primarily in extremities (feet more than hands), though can involve face and other areas 1, 2, 3
- Paradoxical temperature perception where patients feel burning but skin is cool to touch during certain phases 3
- Episodic nature with symptom flares triggered by warmth, physical activity, or dependency of limbs 1, 2
- Erythema and warmth during acute episodes, though between episodes skin may appear normal or cool 2, 3
Diagnostic Workup
The diagnosis is primarily clinical, based on history and physical examination during a symptomatic episode, as there are no specific diagnostic tests. 2
Essential diagnostic steps include:
- Complete blood count to evaluate for thrombocytosis (elevated platelets), which can cause secondary erythromelalgia 2
- Blood glucose testing to rule out diabetic neuropathy as an alternative diagnosis 1, 2
- Autoimmune screening with ANA and ENA to exclude lupus erythematosus 2
- Medication review for triggering drugs including calcium channel blockers and ergot derivatives 2
- Neurophysiological testing with quantitative sudomotor axon reflex testing and thermoregulatory sweat testing, which shows abnormalities in 90% of patients 2
- Genetic testing for SCN9A mutations, particularly if onset in childhood/adolescence or family history present 2
Treatment Algorithm
First-Line Management
Avoid triggers as the primary intervention: heat exposure, tight footwear, excessive exercise, and prolonged standing. 1
Elevate extremities during symptom flares to reduce vascular engorgement. 1
Use cooling measures safely—avoid ice water immersion or powerful fans, as excessive cooling increases risk for tissue damage and ulcerations. 1
Pharmacological Treatment
First-line medications include gabapentin, pregabalin, or duloxetine for neuropathic pain control. 1, 3
- Gabapentin combined with indomethacin and topical lidocaine compounds showed excellent response in documented cases 3
- Aspirin may be particularly effective for erythromelalgia associated with thrombocythemia 1
- Topical treatments can be used as first-line therapy to alleviate erythema and pain 1
Supportive Care
Address sleep disturbance, anxiety, and depression, which are common comorbidities requiring appropriate management. 1
Daily foot inspection is essential to monitor for ulceration development, particularly in patients with sensory loss. 1
Critical Pitfalls to Avoid
Never recommend ice water immersion or direct ice application—this causes tissue ischemia and increases ulceration risk. 4, 1
Avoid footbaths that induce skin maceration. 1
Do not allow patients with sensory loss to walk barefoot or wear shoes without socks. 1
Never use chemical agents or plasters to remove corns and calluses without professional supervision. 1
Alternative Diagnosis Consideration
If symptoms do not fit erythromelalgia pattern, consider:
- Diabetic small fiber neuropathy, which causes burning feet but typically with consistent warmth and progressive sensory loss 1
- Cutaneous sensory disorder, which presents with disagreeable skin sensations but lacks the episodic vascular changes 5
- Sensitized C nociceptor syndrome, which can cause chronic burning pain with skin warming but lacks the episodic cool-to-touch phases 6
The key distinguishing feature is the episodic nature with paradoxical temperature perception and the cool-to-touch skin during symptomatic periods, which is characteristic of erythromelalgia rather than other neuropathic conditions. 2, 3