Only a small number of studies that have investigated the prevalence of EM, with four studies conducted to date. The mean of all the studies combined results in an EM estimation incidence of 4.7/100,000 with a mean of 1 : 3.7 of the male to female ratio, respectively. In 1997 there was a study conducted in Norway that estimated that the annual incidence of 2/100,000, with a 1 : 2.4 male to female ratio in this study population, respectively. In 2009 there was a population-based study of EM in the USA (Olmsted County, Minnesota), that reported that the annual incidence was 1.3/100,000, with a 1 : 5.6 male to female ratio in this study population, respectively. The incidence in this study of primary and secondary EM was 1.1 : 0.2 per 100 000 people per year, respectively. A study of a single centre in the south of Sweden in 2012, showed the overall annual population-based incidence was 0.36/100,000. In New Zealand (Dunedin) a study estimated that in 2013 the incidence of EM is 15/100,000, with a 1 : 3 male to female ratio in this study population, respectively. This last study has an estimation that is at least ten times higher than the prevalence previously reported. This study recruited individuals based on self-identification of symptoms (after self-identification, patients were invited for an assessment of an EM diagnosis), instead of participants that are identified through secondary and tertiary referrals as in the other studies. Prevalence in China Epidemic EM appears quite common in female middle school students of southern China, most likely due to a sharp decline in temperature following by a rapid increase of temperature. It has been postulated that epidemic<unk>  might be related to a poxvirus (ERPV) infection. The disease was characterized by burning pain in the toes and soles of the feet, accompanied by foot redness, congestion, and edema; a few patients had fever, palpitations, headache, and joint pain. 60.6% of patients had a common cold before the onset of<unk>  and 91.2% had pharyngitis. For temperature-related theory, the acral (foot and hand) small superficial arteries intensely constrict and dilate during the sharp decline of temperature, whereas a sharp increase of temperature, the intense expansion of capillaries irritate the nerve endings around, and thus lead to syndromes including (first and second degree) burning pain, increased temperature, erythema and swelling.
Erythromelalgia
Coxalgia
Pathergy
Chromesthesia
Pressure urticaria
Heat urticaria
Onycholysis
Allodynia