(Fig. 1a). The pain and erythema were aggravated by exercise or by standing for a long time, and were relieved by immersion of the feet in cold water. Before the occurrence of swelling and bullae of the legs, he had frequently immersed affected areas in cold water. Painful erythema of both feet had occurred from the age of 3 years, and had progressed with age, greatly restricting daily and social activities. He avoided wearing socks and shoes, and avoided physical activity for fear of developing heat-induced painful erythema of the legs. There was no history of familial occurrence. He usually had more severe symptoms in the ankles and feet. During flares, symptoms frequently extended up to the calves. At high school he had attempted suicide because of the intractable skin problem that gave him no hope of returning to normal life. On infrared thermographic imaging, hyperthermic change was observed on the anterior surface of the lower legs. Physical examination and laboratory findings produced no evidence for infectious, neurological or occlusive vascular disorders. Skin biopsy of an erythematous swollen patch on the right calf revealed a perivascular inflammatory infiltrate with vessel dilatation in the papillary dermis. Primary EM was diagnosed, and the oedema with bulla on the legs was suspected to have been caused by frequent immersion in cold water.

After empirical antibiotic therapy and leg elevation, the oedema and bulla of the legs slowly subsided somewhat, but the severe painful erythema did not improve despite additional treatment for 1 years with various medications including aspirin, propranolol, amitriptyline, sertralin and venlafaxine. In 2000, he was admitted for a trial of intravenous lidocaine infusion to predict subsequent response to oral mexiletine. During the infusion, heart rate, blood pressure and electrocardiogram were monitored and lidocaine 450 mg was infused intravenously over 1 h. After infusion of lidocaine, a visual analogue scale (VAS) score of his pain decreased from 8⁄ 10 to 6⁄ 10. From the next day, he commenced oral mexiletine 300 mg twice daily, titrated up to 300 mg three times daily. He described a dramatic improvement of pain within 1week of administration of oral mexiletine, and gradual improvement of the erythema and warmth of the legs over several weeks (Fig. 1b). The intensity of pain was reduced to about 4⁄ 10 on the VAS score 3 months after the start of oral mexiletine, and improvement of pain (VAS score 3–4) has been sustained for 3 years with mexiletine 600–900 mg daily.