Erythema ab igne Caused by Frequent Hot Bathing

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An 18-year-old woman, a high school student, had had asymptomatic hyperpigmented lesions on her feet, lower legs, upper thighs and buttocks for 3 months. She was otherwise healthy and was not on medication. She did not apply lotions or medicaments to her skin. She also denied applying hot bottles, heating pads or heating blankets to her skin or using other external heating devices. Physical examination revealed symmetrically distributed reticular hyperpigmentation on a faint erythematous background spanning from the buttocks down to the mid-thighs and from the mid-lower legs down to the feet with sparing of the knees and the surrounding skin (Fig. 1). On further questioning, she reported having started to take a hot bath for 60 to 90 min in a bathtub nightly 6 months previously. The bathtub was not deep, so her knees and chest remained above the water when she was bathing, and distribution of the skin lesions corresponded to the areas that were immersed in the water. Skin biopsy specimens were taken from a lesion on her left buttock and left ankle. The microscopic ® ndings of the two specimens were similar, showing hyperkeratosis, epidermal thinning with loss of rete ridges, basal hyperpigmentation and dermal oedema. Slight pigment incontinence and a mild super® cial perivascular lymphocytic in® ltrate were also revealed. Stain for elastin showed an increased amount of elastic ® bres in the upper and middle dermis. Based on the clinical manifestations and microscopic ® ndings, a diagnosis of erythema ab igne was made. The patient was instructed not to take hot baths. Her skin lesions gradually faded during the following months.