Erythromelalgia is a rare neurovascular condition characterized by intermittent episodes of intense burning pain, erythema and raised skin temperature that primarily affects the feet and hands. It more commonly affects the feet than hands. It was first described by Silas Weir Mitchell in 1878 and is sometimes called Mitchell’s disease. The incidence rate is reported as ranging from 0.36 to 1.1 per 100,000 people.
Clinical Features:
Tends to occur in ‘attacks’ of recurrent burning pain, erythema and increased skin temperature that lasts for minutes to hours to sometimes days, usually following exposure to a warm environment or a trigger. Typically the attack starts with an itching sensation which progresses to more severe pain and the burning pain. The foot or hand becomes warm, tender and swollen. It takes on a reddish and sometimes mottled colour. There can be a painful deep-aching of the soft tissue that radiates. Cooler environments provide relief.
The flare-ups or ‘attacks’ can be quite disabling and have a significant impact on quality of life and the ability to carry out the activities of daily living. They may become housebound during an attack and may not be able to wear shoes.
Types of Erythromelalgia:
• Primary: autosomal dominant inherited disorder; the pain and redness are usually symmetrical and episodic; mainly affects the feet at the beginning and may spread to legs; later the hands and even ears may be affected; can be early-onset (occurring in the first decade) or late-onset (in the second decade); some are idiopathic and in others there is a mutation of the SCN9A gene have been found which indicates that this is a kind of ion channel disorder; severity might progress with age and become more of a constant problem.
• Secondary: acquired disorder that is associated with systemic diseases or drug side effects; such as myeloproliferative diseases (eg polycythemia vera); other diseases (eg hypertension, diabetes, systemic lupus erythematosus, rheumatoid arthritis, gout); drugs (eg nifedipine, verapamil); more commonly affects older people; typically more mild than primary type.
Pathophysiology:
Primary: The SCN9A gene mutation(s) underlies the pathophysiology as SCN9A encodes a voltage-gated sodium channel alpha-subunit which is mainly expressed in the nociceptor of peripheral nerves; these mutations will alter the electrophysiologic properties of the ion channel making it easier to open to lead to the neuron being hyperexcitable. This leads to the pain and redness of erythromelalgia.
Secondary: The pathophysiology of the secondary type is less clear but involves abnormalities of vascular dynamics, increased number and abnormal function of platelets, increased vasoactive substances and increased pro-inflammatory mediators.
Differential diagnosis: regional complex pain syndromes, Buerger’s disease, Grierson Gopalan Syndrome, small fiber peripheral neuropathy, Fabry’s disease, Raynaud phenomenon, cellulitis
Complications:
Those with erythromelalgia will often immerse the foot in cold water to get relief and this can predispose to chilblains, maceration of the skin and if done excessively may lead to necrosis and secondary infection.
Treatment:
Triggers of the erythromelalgia, such as warmer temperatures, hot drinks, alcohol and spicy foods should be avoided. Elevation of the limb can sometimes give relief.
Air conditioning and cooling fans as well as gel packs can give some relief and are safer than icy water immersion.
For primary erythromelalgia, pain management is often challenging with the response to different medications being variable.
NSAIDs are often tried but tend not to help.
Sodium channel blockers such as mexiletine and lidocaine may help some
Anticonvulsant agents, such as carbamazepine and gabapentin, may help some.
Topical agents such as capsaicin or ketamine cream may be helpful in some cases.
Sympathetic block and sympathectomy may be tried in those with severe symptoms, but results have been mixed.
In September 2013, AlgoTherapeutix announced a trial of their drug ATX01 (topical amitriptyline hydrochloride 15%) for erythromelalgia.
For secondary erythromelalgia, management is directed at the underlying condition. Aspirin is often tried to help.
Consultation with pain management specialist is recommended. Mind-body therapies can help with coping with the condition.
External Links:
Erythromelalgia (Podiatry Arena)
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