IntroductionErythromelalgia is characterized by the triad of intense burning pain, marked erythema and increased skin temperature (1,2) . Patients describe severe tingling or neuropathy-like pain (2) which generally affects the extremities: the feet more frequently than the hands (1,2) but also the ears and face (3). It is generally bilateral but can be unilateral, particularly in secondary cases (1). Warming up, exercising and relying on the legs are aggravating factors while cooling and elevating the feet are relieving factors (3,4). Its course is often intermittent and the typical constellation of symptoms only appears during flare-ups (1,2) which tend to occur late in the day (sometimes they also continue during the night), at specific temperatures. Frequent immersion in ice water, learned by patients to be a mitigating factor, can cause skin maceration, non-healing ulcers, infection, necrosis, and ultimately amputation (5). The onset of the disease may be gradual. Some cases remain mild for decades; others, about a third, start quickly, begin to spread, and become disabling within a few months (2,6). However, even mild cases can cause sleep disturbances and limit daily activities (1). Patients with erythromelalgia have higher rates of morbidity and mortality than the general population (2). Erythromelalgia is a rare clinical syndrome (4): the estimated incidence varies from 0.25/100,000 in Norway (7) to 1.3/100,000 in the United States (8). Women are affected more frequently than men (2.0 to 0.6 per 100,000) (8). It is classified as either primary or secondary (1): primary erythromelalgia begins spontaneously at any age; Secondary erythromelalgia is associated with other diseases (e.g. autoimmune diseases) (1). Primary erythromelalgia is a category...... middle of paper ......, Chen Y, Xie NC, Wang LJ. Botulinum toxin type A for the treatment of trigeminal neuralgia: results of a randomized, double-blind, placebo-controlled trial. Cephalalgia: an international journal on headaches 2012: 32: 443-450.26. Simpson, LL Identifying the Characteristics Underlying the Potency of Botulinum Toxin: Implications for New Drug Design. Biochemistry 2000:82:943-953.27. Guyer BM. Mechanism of botulinum toxin in chronic pain relief. Current Pain Review 1999:3:427-431.28. Aoki KR. Examination of a proposed mechanism for the antinociceptive action of botulinum toxin type A. Neurotoxicology 2005:26:785-793.29. Zhang L, Wang WH, Li LF, Dong GX, Zhao J, Luan JY, Sun TT. Long-term remission of primary erythermalgia with R1150W polymorphism in SCN9A after chemical lumbar sympathectomy. European Journal of Dermatology: EJD 2010:20: 763-767.