Huynh N, Sarma D, Huerter C. (2011). Erythema ab igne: a case report and review of the literature. Cutis 88(6):290-2, PMID:22372168 [PubMed – indexed for MEDLINE]


Erythema ab igne (EAI) is a rare condition since the advent of central heating. Its incidence has been rising as heating sources are being used to treat chronic pain. Multiple activities that chronically expose patients to heating sources also have been documented with this condition. We present a case of EAI induced by the use of an electric blanket.

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Erythema Ab Igne: A Case Report and Review of the Literature

Nhi Huynh, MD; Deba Sarma, MD; Christopher Huerter, MD

Erythema ab igne (EAI) is a rare condition since the advent of central heating. Its incidence has been rising as heating sources are being used to treat chronic pain. Multiple activities that chroni- cally expose patients to heating sources also have been documented with this condition. We present a case of EAI induced by the use of an electric blanket.

Cutis. 2011:88:290-292.

Case Report

A 53-year-old white woman presented to the derma- tology clinic with discolored skin over the right thigh that extended down to the calf and had been present for many months. She reported mild tenderness of the skin and denied exposure to heating ducts and/ or fireplaces at home or work. She did admit to using an electric blanket off and on for several years with direct contact on the affected skin. She denied any treatment to the affected skin. Physical examination revealed reticular, erythematous, and hyperpigmented patches on the mid and distal right lower extremity (Figure 1). Histopathologic examination of the skin   of the lateral right calf revealed rare dyskeratotic cells, keratinocytic melanosis, minimal pigmentary incontinence, and focal upper dermal perivascular chronic inflammation with no notable atypia in the epidermis (Figures 2 and 3). Elastic stain (Verhoeff- van Gieson) revealed a considerable increase of elastic tissue, especially in the mid dermis (Figure 4). Iron stain (Prussian blue) was negative (not shown). The patient was advised to discontinue use of   the electric blanket and other sources of external heat on the skin.

From Creighton University Medical Center, Omaha, Nebraska. Dr. Huynh is from the Department of Internal Medicine, Dr. Sarma is from the Department of Pathology, and Dr. Huerter is from the Department of Dermatology. The authors report no conflict of interest.

Correspondence: Christopher Huerter, MD, Department of Dermatology, Creighton University Medical Center, 601 N 30th St, Ste5700,  Omaha,  NE68131 (


Erythema ab igne (EAI) is a rare condition character- ized by reticular, erythematous, and hyperpigmented patches resulting from chronic exposure to external heat sources.1’2 Before the advent of central heating, EAI was once considered a common condition, most often found on the distal extremities of individuals  who stood or sat close to burning stoves or open fires.2 Since the emergence of central heating, burning stoves or open fires are no longer a common cause of EAI; other sources of heat have been identified. Cases of EAI have been identified with repeated  application of hot water bottles3 or heating pads30 in the treatment of chronic pain, such as backache that is associated with metastatic malignancy,3’6 pancreatitis,3’4’7 or peptic ulcer disease. Certain occupations that chronically expose workers to external heat sources such as silversmiths, jewelers, bakers, foundry workers, and kitchen workers also have given rise to cases of EAI.1 Erythema ab igne also has been reported in individu- als using electric space heaters,2 car heaters,1’8 heated recliners,3’9 heating/cooling blankets,1’10 heated popcorn kernels,3’11 hot bricks,1 infrared lamps,1 wood stoves,1 coal   stoves,1     electric   stoves/heaters,1     peat   fires,1 steam radiators,1 and most recently laptop computers placed on the users’ thighs or propped legs.3’12″14





The pathogenesis of EAI is not yet understood; however, it is suggested that chronic heat exposure denatures  DNA  in  squamous  cells  in conjunction with UV radiation.3 A single episode of heat exposure  is insufficient to induce a burn or skin manifestation associated with EAI. Chronic heat exposure is needed to accumulate the damages, generating an initial pattern of erythema that then progresses to reticular hypopigmentation and hyperpigmentation. Although infrequent, subepidermal bullae1’15 and diffuse hyper- keratosis may occur. In severe cases, poikiloderma; ulceration; and secondary  skin  malignancy,  such as squamous cell carcinoma in situ, squamous  cell carcinoma,1’16’17 and neuroendocrine carcinoma (Merkel cell carcinoma),1’3 may result, though these malignancies are quite rare.

Histologically, EAI exhibits variable features that are nonspecific. In the early stages, EAI may appear normal on hematoxylin and eosin stains.3  However,   it also may reveal increased epidermal atrophy, rete effacement, basal vacuolar changes, and pigment incontinence.1’3’17 The dermis may be infiltrated by lymphocytes, melanophages, histiocytes, and neutro- phils, with dilation and congestion of the postcapil- lary venules.3 Perhaps the most distinguishing feature of EAI is the increased elastic tissue in the upper  and mid dermis,18 and the  presence  of  squamous cell atypia,3’17 which resembles actinic keratoses.2’17 Hyaluronic acid and iron deposition also have been described, though the deposition of iron may be anatomically related to the  distal  extremities.1’3  In the presence of these nonspecific features, a clinical correlation is an important factor in the diagnosis  of EAI.3

Erythema ab igne is more common in females and more likely to occur in patients who are overweight. Most of the patients with EAI are asymptomatic or present with a mild sensation of burning or pruritus.1 The differential diagnosis of EAI includes solar elas- tosis, erythema dyschromicum perstans, acanthosis nigricans, actinic keratoses, livedo reticularis,   livedo vasculitis, poikiloderma atrophicans vasculare, and cutaneous reactive angiomatoses.19

Erythema ab igne has an excellent prognosis. The most important treatment of EAI is immediate removal of heat sources to prevent further damage.1’3 5-Fluorouracil cream has been shown to be effective in eliminating atypical squamous cells in EAI.3’20  In severe cases in which pigmentation persists, tretinoin or hydroquinone could be used topically.2 Biopsy is needed if there is evidence of malignancy, such as unrelenting ulcer, infiltrated borders, or nodules. In addition, the presence of EAI may be the first clue to an undiscovered malignancy,6’9 such as meta- static adenocarcinoma, adenocarcinoma of the rec- tum, or pancreatic cancer, as a  heating source such as hot water bottles is repeatedly used to relieve chronic pain induced by these undiagnosed can- cers. These types of malignancies are especially more suspicious when the lesions of EAI are    located on the abdomen, flank, or mid back.1 Thus it is important to do a thorough patient history and evaluation to properly treat and follow patients with EAI.2


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Huynh N, Sarma D, Huerter C.(2011). Erythema ab igne: a case report and review of the literature Cutis 88:290-92, PUBMED.