Symmetrical Reticulated Lower Extremity Rash
Am Fam Physician. 2019 Jul 1;100(1):51-52.
A healthy 30-year-old woman presented with a rash over both lower extremities (Figure 1) that began two months earlier. The rash was slightly itchy but not painful. She lived in a cold area and reported sitting in front of an electric heater for two to three hours daily over the previous two months.
On physical examination, the skin looked mottled, blotchy, and reticulated. It had a nonblanching network pattern and a blue-gray discoloration.
Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?
A. Cutaneous lupus erythematosus.
B. Discoid lupus erythematosus.
C. Erythema ab igne.
E. Livedo reticularis.
The answer is C: erythema ab igne. Erythema ab igne, also known as toasted skin syndrome, is a rare condition that results from prolonged and repeated exposure to thermal radiation. The heat exposure, usually between 109°F and 117°F (43°C to 47°C), is not intense enough to burn the skin but can result in skin involvement in a pattern that mirrors the heat source. Commonly affected areas include the anterior calves (fires), anterior thighs (laptops), and back or peripheral joints (heating pads or bottles). Less common sites include the face and the arms or palms of cooks. Abdominal and pelvic involvement has been reported in patients with visceral malignancies, peptic ulcer disease, or chronic pancreatitis, usually due to water bottles held against the abdomen or pelvis to reduce pain.
The affected area has a mottled, net-like, nonblanching pattern of blue-gray discoloration, sometimes with associated erythema and scale. Erythema ab igne is usually asymptomatic, but some patients
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This series is coordinated by John E. Delzell Jr., MD, MSPH, Associate Medical Editor.
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