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December 3, 2010

BehindTheMedspeak: Toasted Skin Syndrome (Erythema ab Igne)


It's an unusual-looking mottled skin condition caused by long-term heat exposure from a laptop computer.

In an article published in the October 2010 issue of the journal Pediatrics, Swiss researchers reported that "a 12-year-old boy [below] developed a sponge-patterned skin discoloration on his left thigh [top] after playing computer games a few hours every day for several months."


"He recognized that the laptop got hot on the left side; however, regardless of that, he did not change its position," noted the scientists.

In the past six years at least 10 laptop-related cases of Erythema ab Igne have been reported.

Below, the abstract of the report in Pediatrics.


Laptop Computer-Induced Erythema ab Igne in a Child and Review of the Literature

We report here the case of a 12-year-old boy with erythema ab igne on his left thigh caused by the use of a laptop computer. This is the youngest of the 10 reported patients with this laptop-induced dermatosis since its first description in 2004. Erythema ab igne is a reticular, pigmented, sometimes telangiectatic dermatosis that is caused by prolonged exposure to a heat or infrared source. In laptop-induced erythema ab igne, the localization on the thighs and asymmetry are characteristic. The heat originates from the optical drive, the battery, or the ventilation fan of the computer.


Below, the abstract of a 2007 report.


Laptop computer-associated erythema ab igne

A 40-year-old woman presented with an asymptomatic reticulated eruption on the thighs. After an extensive workup, she was diagnosed with erythema ab igne caused by laptop computer use. The eruption ultimately cleared several months after discontinuation of direct placement of the laptop computer on her thighs. Erythema ab igne is becoming increasingly associated with exposure to modern heat sources. A thorough history of patients with suspicious lesions should include questioning for contact with alternative heat sources to avoid an unnecessary workup for this condition.


Below, the original 2004 paper referenced in the Pediatrics report, along with its accompanying image.



Erythema ab igne induced by a laptop computer

Erythema ab igne (EAI) is a reticular, telangiectatic, pigmented dermatosis occurring after long-term exposure to infrared radiation that is insufficient to produce a burn. We present an unusual case of laptop computer-induced EAI.

A 50-year-old white man presented with a 2-week history of an asymptomatic patch on his left leg. On physical examination, there was a fairly well-defined, brown, mildly erythematous, reticulated patch on the left anterior thigh. This asymptomatic eruption was noticed 2 weeks after the patient purchased a new laptop computer. The patient is a systems analyst who spends a considerable amount of time each day using his computer. He frequently placed the computer on his anterior thighs while at work. He stopped resting the computer on his thighs after he repeatedly experienced discomfort from heat emitted from the base of the laptop.

The lesion was isolated to the left anterior thigh, because the heat source (optical drive) was located on the left base of the computer. EAI often begins as mild localized erythema. Repeated exposures to moderate heat may result in reticulate erythema, hyperpigmentation, telangiectases, scaling, and atrophy3; subepidermal bullae have also been reported.

Historically, EAI was commonly seen on the shins of those who worked in front of open fires or coal stoves. EAI may appear on the exposed skin of individuals who sit too close to fireplaces, space heaters, steam radiators, and wood-burning stoves.5 It is also seen after repeated application of hot water bottles and heating pads used to treat ailments such as abdominal pain and chronic back pain. Furniture with a built-in heating unit, a car heater, and a heating blanket are additional reported sources of EAI.

Histopathologic changes include hyperkeratosis, epidermal atrophy, squamous atypia, and interface dermatitis with necrotic keratinocytes. An increased amount of dermal elastic tissue may also be seen. Histologically, EAI is similar to actinic keratosis, and these lesions have therefore been called “thermal keratoses.” The similarities between actinic and thermal keratosis suggest that heat may induce epithelial changes as a result of clonal mutation in the same way that ultraviolet light produces epithelial changes. Rare cases of squamous cell carcinoma (SCC) and Merkel cell carcinoma arising in lesions of EAI have been reported. Thermally induced cancers are usually SCCs and occur even after 30 years.

This case illustrates an unusual modern demonstration of EAI. It is important for physicians to be aware of the new and evolving heat sources causing thermal-related cutaneous injury. Patients should be instructed to discontinue close contact with sources of infrared radiation. A biopsy should be performed if there is any evidence of cutaneous malignancy. 5-Fluorouracil cream has been reported to clear epithelial atypia in EAI.


Links to four reported other cases — two this year, one from 2009 and another from 2008 — may be pursued here.

Based on case report rejection letters I received in years past, I'd say it's time to move on and no longer consider Erythema ab Igne a reportable condition.

Of course, if I'm still in academia with another affected patient and laboring on building a case for tenure, I'd disagree — vehemently.

December 3, 2010 at 04:01 PM | Permalink


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It's what I do. Bill to follow shortly.

Posted by: bookofjoe | Dec 3, 2010 5:52:48 PM

I had undiagnosed anterior thigh pain for 1-1/2 years that woke me up every 45 minutes to an hour through the night, every night, and the only 'cure' for the pain was walking and heat. I developed exactly the same pattern and my doctor said that my suggestion that it was caused by the rice sock I was putting on my thigh was "absurd" and he took photos of the site to show the other doctors in his practice. Together they couldn't figure out what was causing the pattern, since they were convinced it wasn't caused by the heat packs.

It's so nice to get confirmation that I was correct in my assessment of the cause of the pattern. Thanks!

Posted by: tracy hartley | Dec 3, 2010 4:45:38 PM

Hot off the press, eh?

Posted by: 6.02*10^23 | Dec 3, 2010 4:37:03 PM

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