Erythema Ab Igne

An 88-year-old woman with a history of senile cardiac amyloidosis was seen in the cardiology clinic for heart failure. During the visit, she reported that she had had persistent pain along the lumbo-sacral region, but more recently pruritus had developed. She had been using a heating pad for symptomatic relief.

Physical examination revealed a reticulated hyperpigmented dermatosis along her lower back (A and B). The patient stated that this rash had been present for several months. The history and physical findings were typical of erythema ab igne.

Erythema ab igne is caused by exposure to heat or an infrared source.¹ This dermatosis has been associated with the use of heating pads, space heaters, electric blankets, laptop computers, and has also occurred in those who sit next to coal stoves or fires.² It is characterized initially by mild erythema followed by a reticulated hyperpigmented lesion that may become atrophic. Although erythema ab igne is usually asymptomatic, it can cause burning and pruritus.¹ Histopathological characteristics include epidermal thinning, basal vacuolar changes, and epithelial atypia.³

Erythema ab igne can be a platform for the development of malignancies. The most common are squamous cell carcinomas, but Merkel cell carcinomas and mixed squamous cell and Merkel cell carcinomas have been documented. A case of cutaneous marginal cell lymphoma has also been reported.⁴ Therefore, close surveillance is warranted, and skin biopsies should be performed to evaluate suspicious lesions. Treatment of erythema ab igne entails removal of the inciting source of thermal injury.²