Bus Driver With an Erythematous, Reticulated Patch on Her Back

Thomas Stasko, MD

Disclosures

October 21, 2002

Discussion of Answer

Erythema ab igne is an area of persistent macular erythema and hyperpigmentation that occurs in skin chronically exposed to heat. It begins as transient erythema that, with continued exposure to the heat source, becomes permanent, with areas of blue, purple, or brown pigmentation in a reticulated pattern.[1] The condition has historically been reported on the inner thighs and legs of women who sat in front of coal stoves and peat fires to keep warm before the advent of central heating.[2] In modern times, it is associated with the use of hot water bottles, heating pads, or furniture with heated cushions.[1,3] Although the condition is often asymptomatic to only mildly symptomatic, there have been case reports of squamous cell carcinoma developing in areas of erythema ab igne: peat-fire cancers on the shins of women exposed to peat- or coal-burning stoves, kangri ulcers from carrying charcoal burners in Tibet, kairo cancers in Japan from similar heaters, and kang ulcers in northwest China from sleeping on hot bricks.[3,4,5]

Diagnosis is usually made by clinical appearance and history. When biopsy is performed, histologic findings in early lesions can include epidermal atrophy, vasodilation, mixed-cell infiltrates in the dermis, melanophages, dermal melanin granules, and hemosiderin. Later on, varying amounts of elastotic fibers and hyperkeratosis with or without dyskeratosis can be seen. One group of investigators reported that interface dermatitis with necrotic keratinocytes and postinflammatory pigmentary alteration were common denominators in this condition.[6]

Other than avoiding further contact with the heat source, there is no effective treatment for erythema ab igne. One article did report the use of 5-fluorouracil to treat dyskeratotic keratinocytes.[7]

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