Erythema ab igne secondary to repeated heating pad use: an image case

Erythema ab igne is a reticular, telangiectatic, pigmented dermatosis caused by prolonged and repeated exposure to infrared radiation. We present a case of erythema ab igne secondary to heating pad use (Fig. 1).

Pathogenesis involves thermal radiation causing damage to superficial blood vessels that subsequently leads to vascular dilation and hemosiderin deposition (1). This condition usually begins as mild localized erythema that often goes unnoticed. Prolonged and repeated exposures to the heat source results in hyperpigmentation and telangiectasia. If the offending heat source is not removed, it can ultimately lead to scaling and atrophy. Subepidermal bullae and rare instances of cutaneous horn with thermal keratosis, squamous cell carcinoma, and Merkel cell carcinoma can also arise from erythema ab igne lesions (3).

The histopathology of erythema ab igne is nonspecific and may appear normal on H and E stain or demonstrate mild acanthosis and hyperpigmentation of basal keratinocytes (4).

The various treatment modalities suggested for erythema ab igne include topical retinoids, with or without topical steroids, and 5-fluorouracil cream. Removal of the offending heat source and topical therapies are effective in resolution of the condition.

Fig. 1 Erythema ab igne occuring over the lower back resulting from repeated heating pad use (2).