Recently, a 57-year-old woman was informed by her husband that she has a discolored area of skin on her back. This discovery followed a prolonged period of back pain, for which she was prescribed an NSAID. When this yielded no relief, she started sleeping with an electric heating pad, held in place by an elastic bandage, to ease the pain.
She reports mild itching in the affected area. She claims to be in good health otherwise and is not taking any medication.
The patient is in no acute distress but has obvious difficulty walking without pain. Covering her back, from the bra strap down, is modest erythema, a reticular pattern of modest hyperpigmentation, and focal areas of mild scaling.
No tenderness or increased warmth is detected on palpation. No notable changes are seen elsewhere on her skin.
What is the diagnosis?
This condition, termed erythema ab igne (EAI), was first described in 18th century women who worked while seated in front of a fire all day—hence the name, which translates to “redness from fire.” Over time, this exposure produced permanent changes on the anterior portions of their legs—similar to those seen in this patient.
Today, the condition can develop in a variety of contexts, all of which involve prolonged, repeated exposure to infrared radiation (eg, electric blankets, hot water bottles, electric space heaters, laptop computers). EAI can also affect the faces and arms of bakers, chefs, welders, and silversmiths working in close proximity to radiation.
This type of heat increases vasodilation in the superficial venous plexus (located in the papillary dermis), which causes hemosiderin to leak into the superficial dermis over time. This permanently stains the skin with a characteristic reticular pattern that mimics the affected vascular pattern. Generally, the darker the patient’s skin, the darker the pattern appears.
EAI more commonly affects women than men, and its diagnosis should prompt further investigation for underlying conditions. Musculoskeletal problems, chronic infection, anemia, or hypothyroidism could be involved.
Treatment, besides avoidance of radiation, includes topical application of retinoids or use of lasers.
In this case, the changes were discovered early enough to be at least partially reversible. In more advanced cases, focal areas of scaling can coalesce into papules or nodules that can undergo malignant transformation to squamous cell carcinoma.
TAKE-HOME LEARNING POINTS
- Erythema ab igne (EAI) is a fairly common condition caused by close proximity to infrared radiation (eg, heating pads, laptop computers, electric space heaters).
- This radiation causes chronic vasodilatation of the superficial venous plexus, which leads to leakage of hemosiderin pigment, permanently staining the skin in a reticular pattern.
- EAI can affect the faces and arms of bakers, welders, chefs, and silversmiths.
- Treatment can be attempted with topical application of retinoids or with use of lasers.