Erythema Ab Igne
A healthy 24-year-old woman presented to the dermatology clinic with a 2-month history of a rash on her shins. The rash was asymptomatic and was more prominent on the left leg. It had first appeared during the winter, at which time the patient had been using an electric heater that was closer to her left leg. The examination was notable for a reticular pattern of hyperpigmentation on the shins that was more prominent on the left leg. The left leg also had scattered, hypopigmented, atrophic scars. No palpable purpura, subcutaneous nodules, or areas of gangrene were present. A skin biopsy showed a perivascular lymphocytic infiltrate with hemosiderin deposition in the upper dermis. A diagnosis of erythema ab igne was made. Erythema ab igne is a dermatosis that results from long-term heat exposure. It manifests as an erythematous or hyperpigmented reticulation that can occur anywhere on the body and can be distributed asymmetrically, depending on the location of the external heat source. It may be confused with vasculitis. The patient was advised to avoid further direct heat exposure. At a 3-week follow-up visit, the hyperpigmentation had decreased, but the hypopigmented scars — which may have been from mild burns — persisted.