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Erythromelalgia

Updated: Sep 12, 2021


Epidemiology

- Primary erythromelalgia = any age

- Secondary erythromelalgia > 40 yo

Pathophysiology


Primary erythromelalgia is caused by mutations in SCN9A, which encodes for the Nav1.7 type sodium channel receptor.


(NB: NAV1.7 in nociceptive neurons and normally amplifies nociceptive pain signals. Mutation leads to hyper excitability of nociceptive neurons --> dilated blood vessels)


Secondary erythromelalgia associated with myeloproliferative disorders. Erythromelalgia presents before the myeloproliferative disorder in 85% of cases.

Can occur with paraneoplastic disorders, autoimmuneneuropathies and rarely diabetes, rheumatologic and infectious diseases.


Presentation


- Intense burning pain of bilateral feet and sometimes hands

- Brought on by warming or hanging the limb downward

- Relieved with cooling and elevation

- Flare-ups last minutes to days, occur late in the day and continue through the night

- Attacks begin with itching --> severe burning pain

- Diagnostic Triad - recurrent, burning pain and warm extremities.

Usually bilateral though can occur unilaterally

Associated with severe erythema and increased palpable heat

Usually episodes once a week or once a month

Disease course is usually highly variable

can be mild and episodic lasting years, or can present suddenly with severe symptoms coming over weeks

Rarely can progress proximally from limbs even involving the face/head

primary erythromelalgia is more common in females - but slightly more common in males in secondary erythromelalgia


Complications

t is possible to get ulceration, necrosis and gangrene as complications of erythromelalgia. Occasionally, wounds can become secondarily infected, which, if severe enough, may lead to amputation.


Examination


Investigations


Erythromelalgia may be an early sign of polycythaemia (raised red cells) or thrombocythaemia (raised platelets), where symptoms may precede diagnosis of the myeloproliferative disorder by 2.5 years. These diseases are detected by full blood count.


If in doubt, a trial of immersing an affected area in hot water for 10–30 minutes may sometimes provoke an attack and support the diagnosis.


Treatment


The underlying cause must be treated where possible in secondary erythromelalgia.

Most cases of primary erythromelalgia are refractory to pharmacotherapy and response to pain therapeutics is variable. Most of these therapies have only been validated in case reports or smaller studies.


Cooling or elevating the extremity may relieve symptoms. Care is needed around cold water immersions, although it will provide temporary relief, it can cause many other serious problems. Frequent immersion into cold water can create a vicious cycle, as the changes in temperature may cause reactive flaring. This can also lead to maceration of the skin, non-healing ulcers, infection, gangrene and amputation.


Topical capsaicin cream has been reported with varying results.


Aspirin – relieves symptoms of erythromelalgia related to thrombocytosis


Sodium channel blockers – mexiletine has been shown to improve pain, especially in patients with V872G mutation


Calcium antagonists – nifedipine, diltiazem


Prostaglandins – misoprostol


Intravenous infusions of nitroprusside, lignocaine (lidocaine) and prostaglandin


Medications used for neuropathic pain


Serotonin re-uptake inhibitors – venlafaxine, sertraline, fluoxetine, paroxetine


Tricyclic antidepressants – amitriptyline, imipramine


Anticonvulsants – gabapentin, carbamazepine


Surgical sympathectomy (a procedure in which the sympathetic nerve fibres are selectively cut)

Thoracic sympathectomy for hands

Lumbar sympathectomy for feet There are no specific guidelines for SCN9A genetic testing, but these can be considered in young patients in whom there is a positive family history and when secondary causes have been excluded. Genetic testing may have impact on family planning given 50% probability of heritability of the condition by offspring.


In most patients with primary erythromelalgia, their symptoms remain refractory to sodium channel blockers and other treatment, and symptoms tend to progress over time. Quality of life can be greatly affected due pain and disability due to pain, secondary tissue damage (ulcers, necrosis, gangrene) or self-harming behaviours can be an issue.

Spontaneous remissions have also been known to occur.


Golden pearls

Erythro - Red, Mel - limbs, Algia - pain

- Also known as erythermalgia

- Primary erythromelalgia with positive family history is known as Weir-Mitchell disease


References / Articles / Resources



gdd



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