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What caused discolored skin on this man’s legs?

Casey J. Barcomb, PA-C

Casey Barcomb practices in the dermatology department of the Woodland Healthcare Clinic, Woodland, California. He has indicated no relationships to disclose relating to the content of this article.

CASE

The patient is a 74-year-old male of Asian descent with a 6-week history of asymptomatic bullae and associated discoloration on his legs. He had been applying a topical neomycin ointment to the areas twice daily but had not noticed any improvement. The patient’s primary care provider had prescribed oral cephalexin, 500 mg 3 times daily for 10 days, but this treatment did not help either.

The medical history included coronary artery disease, hypertension, and dyslipidemia. The patient underwent coronary artery bypass surgery, in which his saphenous veins were harvested, 21 years ago. He admitted to having varicella as a child. There was no history of thyroid disease, anemia, or any metabolic conditions. The patient denied any history of skin problems and reported that none of his contacts had a similar rash. He had not been traveling recently. His main hobby was reading, and he enjoyed the comfort of a good book and the warmth produced by his space heater in the cold winter months.

Physical examination revealed a symmetrical, hyperpigmented, reticular brown discoloration located on the medial legs (see Figure 1). The involvement spanned the inguinal folds down to the mid-tibia bilaterally. A firm, 20 3 15-mm bulla was located on the left leg, with a few collapsed bullous lesions adjacent to it. The skin was not sclerotic and was asymptomatic when palpated. The rest of the skin was free of disease.

WHAT IS YOUR DIAGNOSIS?

Linear morphea
Allergic contact dermatitis secondary to neomycin use
Livedo reticularis
Erythema ab igne

DISCUSSION

This patient had erythema ab igne. Upon further questioning, the patient admitted to having a new, tall columnar space heater, which he placed approximately 12 inches in front of his legs while reading on the couch. He reported a 6-month history of reading in front of the heater.

Erythema ab igne is a dermatologic condition triggered by chronic exposure to infrared heat. Affected patients have a history of long-term, direct, or close contact with a heat source, such as a heating pad, fireplace, or space heater. The exposure leaves the patient with a brown, asymptomatic, reticular hyperpigmentation in the heated area. In more pronounced cases such as this one, bullae will be present.

Comment Although linear morphea can cause some dyspigmentation of the skin, it is usually firm and fibrotic to palpation. In this case, there was no fibrosis. Neomycin-containing products are notorious for causing allergic contact dermatitis. Given the patient’s history of use, this diagnosis had to be seriously considered. Neomycin dermatitis manifests as an erythematous, pruritic, vesicular rash, however, and these signs and symptoms are not present in our patient. Livedo reticularis is characterized by a generalized red or blue “fishnet” pattern without hyperpigmentation. The legs are commonly affected, and painful ulcerations are occasionally present. Cold temperatures will exacerbate the condition. Livedo reticularis can be associated with coagulopathies and autoimmune disease.

Treatment The patient was instructed to avoid sitting in front of his heater in the future. The dyspigmentation of erythema ab igne may fade to some degree, but usually it persists for months to years. Topical hydroquinone 4% cream may be applied to help encourage fading. This patient’s case demonstrates how important it is for the clinician to take a thorough history and to be familiar with this increasingly common condition. JAAPA

Joe R. Monroe, PA-C, MPAS, department editor