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Laptop-induced erythema ab igne: Report and review of literature

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Laptop-induced erythema ab igne: Report and review of literature
Ryan R Riahi1 MD, Philip R Cohen2 MD
Dermatology Online Journal 18 (6): 5

1. Medical School, The University of Texas Medical Branch, Galveston, Texas and Tulane University Hospital, New Orleans, Louisiana
2. The University of Houston Health Center, University of Houston, Houston, Texas; The Department of Dermatology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas; and The Department of Dermatology, University of Texas-Houston Medical School, Houston, Texas


Erythema ab igne is an erythematous, reticular hyperpigmentation that results from prolonged thermal radiation exposure insufficient to cause a burn. Historically, lesions were found on individuals exposed to open fires or stoves, but more recently, erythema ab igne has been described in patients using portable electronics devices including laptops. We report a 21-year-old woman who presented with net-like hyperpigmentation on her thighs caused by prolonged laptop use. We also review the literature that describes other individuals with laptop-induced erythema ab igne and discuss the features of this condition.


Erythema ab igne is a condition that results from chronic low-grade heat exposure in which the reticulated, cutaneous macules are initially erythematous and subsequently hyperpigmented. Although the exact mechanism remains unknown, heat exposure may induce damage to superficial blood vessels, leading to dilation and deposition of hemosiderin in a reticulate distribution [1]. The lesions can begin as evanescent, net-like erythema that gradually darkens. With chronic heat exposure, lesions of erythema ab igne can become atrophic, hyperpigmented, or ulcerated with scaling and telangiectasias [2, 3, 4, 5]. Lesions are typically asymptomatic. However, burning and pruritis have been reported in some individuals.

Erythema ab igne is caused by prolonged thermal radiation exposure insufficient to cause a burn. Historically, lesions developed on the shins of individuals who worked near coal stoves or open fires [2]. More recently, lesions have been reported to develop on the arms and face of cooks exposed to stoves, trunk or limbs of intensive care unit patients using heating blankets, and shins of elderly individuals sitting near fireplaces or radiators for prolonged periods of time [6, 7]. Erythema ab igne can occur in the setting of chronic pain; lesions can develop on the abdomen or back as a result of using heating pads or hot water bottles [6, 8].

Modern causes of erythema ab igne include the use of electronic devices. Laptop-induced lesions are typically found on the thighs and can be unilateral because of the location of the optical drive, battery, or heating elements of the laptop [9]. Recently, reports of erythema ab igne from a cellular phone have been described [10].

The diagnosis of erythema ab igne is clinical. A history will typically reveal chronic exposure to thermal radiation. Treatment involves removing the heat source to prevent further exposure. Removal of the heat source after the initial stages allows resolution of the red banding. However, prolonged exposure often results in permanent hyperpigmentation [6]. Chronic erythema ab igne may have an increased risk of malignant transformation [11]. We report a 21-year-old woman who presented with net-like hyperpigmentation on her thighs caused by prolonged laptop use and review features of laptop-induced erythema ab igne.

Case report

A 21-year-old woman presented to clinic with a two year history of gradually developing, net-like hyperpigmentation on her thighs.. She does not take any medications and denied any other symptoms.

Figure 1Figure 2
Figure 1. Overhead view of erythema ab igne in a 21-year-old woman presenting as net-like hyperpigmentation on the thighs, more pronounced on the left.

Figure 2. Side view demonstrating clear proximal demarcation of hyperpigmented lesions of erythema ab igne with a reticulate pattern on the distal thighs.

Physical examination demonstrated a reticulated pattern of hyperpigmented lesions on the thighs bilaterally (Figures 1 and 2). There was more hyperpigmentation on the left thigh than the right. There was a clear proximal demarcation with a reticular pattern more distally on the thighs. The diagnosis of erythema ab igne was suspected.

Figure 3Figure 4
Figure 3. Overhead view of a laptop positioned on the woman’s thighs; the area that the computer covers corresponds to the demarcation of the lesions.

Figure 4. Side view of a laptop positioned on the patient’s thighs corresponding to the distribution of her erythema ab igne lesions.

Upon further questioning, the patient reported she was a college student and would sit with a laptop on her thighs for prolonged periods of time. The lesion borders were consistent with the positioning of a laptop on her thighs (Figures 3 and 4). The diagnosis of erythema ab igne was confirmed.

The patient was counseled to avoid positioning the laptop on her thighs. She was later seen for follow-up and did not demonstrate resolution of her hyperpigmentation. Despite discontinuing laptop use on her thighs, the lesions remained hyperpigmented without any decrease in the severity of the pigmentation.


Erythema ab igne is characterized by pigmented, reticulate skin lesions. The lesions result from prolonged or repeated heat exposure [12]. Typically, mild heat in the range of 43-47°C can cause the condition. Modern laptops can generate temperatures in this range. Indeed, laptops with powerful processors can reach temperatures of 50°C and be associated with burns [2, 13]. Positioning of the laptop on the thighs can allow for direct exposure to the heating elements of the laptop, which include the central processing unit (CPU) and the graphics processing unit (GPU) [14]. Furthermore, occlusion of the cooling-fan by the thighs can increase the temperature of the laptop by preventing the free flow of air [1]. Our patient demonstrated lesions more prominent on the left thigh and — to a lesser degree — on the right thigh, corresponding to the location of the CPU and GPU for her particular laptop.

In our survey of the literature, there are approximately 15 reports in the Danish, English, French, German, Portuguese, and Swedish journals of laptop-induced erythema ab igne (Table 1) [1-4, 9, 14-22]. In these reports, 9 of the 15 patients were women (60%) with an average age of 25 years at diagnosis. Men (6 of the 15 patients, 40%) who developed laptop-induced erythema ab igne averaged 20 years of age when the condition was discovered. Duration of laptop exposure ranged from two weeks to two years.

Most cases of laptop-induced erythema ab igne occurred on the thighs (14 of 15 cases, 93.3%). Typically, lesions of laptop-induced erythema ab igne involve only one side of the leg corresponding to the location of the laptop’s heating element [5, 7]. Whereas both thighs were reported to develop erythema ab igne, the left anterior thigh was the most frequent site of involvement (53%, 8 patients). Involvement of the right anterior thigh (27%) and equal involvement of both thighs (13%) occurred in 4 and 2 patients, respectively. There is one report of an 18-year-old girl who developed localized pigmentation on her left breast related to the use of her laptop computer while reclining [16].

Computer-related dermatoses can include allergic contact dermatitis, erythema ab igne, friction-induced hand lesions, and screen dermatitis [12]. In recent years, an increasing number of individuals with laptop-induced erythema ab igne have been reported. Most patients (12 patients) who developed laptop-induced erythema ab igne were 26 years of age or younger. Patients may provide a history of placement of their laptop on their thighs for a prolonged period of time. Middle school aged adolescents (14 years and less) might be more likely to utilize a desktop at school or home rather than a laptop; patients in this age range (3 patients, 20%) represent a minority of the patients affected by laptop-induced erythema ab igne.


Erythema ab igne is a macular, erythematous and hyperpigmented, reticulated condition occurring after chronic thermal radiation exposure. We present a woman who developed laptop-induced erythema ab igne and characterize the populations affected by this type of laptop-induced lesion. Patients who present for evaluation of erythema ab igne on the thighs should be questioned about a history of prolonged laptop use. Furthermore, all laptop users should place laptops on a solid surface and avoid prolonged contact with the body.


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