Erythema ab igne is a skin lesion that develops at a site which has been exposed to heat over a prolonged period of time.
(1) The affected skin shows a macular area with a reticular pattern.
(2) The area shows patchy erythema or hyperpigmentation.
(3) The area is painless, nonblanching and nonpruritic.
(4) There is a history of repeated exposure to a low level of heat for a prolonged period of time.
Usually the level of heat exposure is insufficient to cause a thermal burn but burns can occur if the exposure is severe enough.
The diagnosis is made by:
(1) Improvement of the area after heat exposure is discontinued, although hyperpigmented areas may not resolve completely.
(2) Other conditions in the differential diagnosis such as livedo reticularis and livedoid vasculitis have been excluded.
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