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PATIENT STORY

A 50-year-old woman presented with bilateral erythematous lesions on the inner aspects of both of her lower extremities (Figures 209-1 and 209-2). The lesions had begun developing approximately 6 months ago. They became progressively more noticeable but remained localized in the inner aspects of the lower extremities. She mentioned using a hot-water bottle in the area to keep herself warm at night when sleeping in bed. Although our working clinical diagnosis was erythema ab igne, clinical entities such as livedo reticularis, poikiloderma atrophicans vasculare, and acanthosis nigricans were in the differential diagnosis. A skin biopsy confirmed the diagnosis of erythema ab igne. The patient was advised to discontinue use of the hot-water bottle on the skin. Over the course of 4 months, her skin lesions started to clear with no further intervention.

FIGURE 209-1

Mottled or meshlike pigmentary changes on the legs of a 50-year-old woman who slept with a hot-water bottle between her legs. (Reproduced with permission from El-Ghandour A, Selim A, Khachemoune A. Bilateral lesions on the legs, J Fam Pract. 2007;56(1):37-39. Frontline Medical Communications. Inc.)

FIGURE 209-2

Close-up of legs in Figure 209-1. (Reproduced with permission from El-Ghandour A, Selim A, Khachemoune A. Bilateral lesions on the legs, J Fam Pract. 2007;56(1):37-39. Frontline Medical Communications. Inc.)

INTRODUCTION

Erythema ab igne (EAI) is a rare skin condition caused by chronic exposure to low-intensity heat that is insufficient to cause burns. Sources of this heat can include hot-water bottles, heating pads, electric blankets, car seat warmers, exposure to open fires, and laptops placed on the users' thighs or propped legs. EAI is typically characterized by pink, reticulated, and hyperpigmented mottled patches in the setting of prolonged exposure to heat. Patients may complain of associated pruritus or paresthesias, or they may be asymptomatic. Treatment is limited and patients are instructed to avoid triggers.

SYNONYMS

Chronic moderate heat dermatitis, chronic radiant heat dermatitis, toasted skin syndrome, fire stains, hot-water bottle rash, laptop thigh.

EPIDEMIOLOGY

  • Rare disease.

  • Women, in particular those who are overweight, are affected more often than men.

ETIOLOGY AND PATHOPHYSIOLOGY

  • The skin findings form as a result of multiple exposures to low-intensity heat.

  • EAI is thought to be caused by damage to superficial blood vessels from external heat, which leads to hemosiderin deposits in the superficial skin, usually in a reticulated pattern.1

  • In the past, EAI was reported in women who were exposed to open fires, fireplaces, or furnaces to cook for extended periods of time.2-5 As a result, most of the lesions would manifest on the medial side of the thigh and ...

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