Erythema ab igne

A 54-year-old man with chronic kidney disease (CKD) presented to a general practice routine visit with a 1-week history of hyperpigmented reticular skin lesions on the inner and posterior faces of both thighs. He also reported symmetrical numbness below the knee level since a few weeks before. No other symptoms were stated. When questioned for possible triggers, the patient mentioned a regular use of a hot water bottle on his thighs due to cold weather. On physical examination were seen brownish, hyperpigmented, web-liked patches spanning across the inner and posterior faces of both thighs (Figure 1), more evident on the left (Figure 2). Posterior tibial artery and dorsalis pedis artery pulses were normal, there were no areas of necrosis and no purpura or subcutaneous nodules were palpable. A presumptive diagnosis of erythema ab igne was made and he was told to stop using the hot water bottle.

Figure 1 Hyperpigmented reticular skin lesions on the inner and posterior faces of both thighs on presentation.

Figure 2 Hyperpigmented reticular skin lesions on the left thigh on presentation.

Erythema ab igne is a skin condition characterized by hyperpigmented rash due to chronic heat exposure, which is reversible upon heat source withdrawal. Livedo reticularis, cryoglobulinemia or livedoid vasculopathy should be considered as differential diagnosis.

A 4-week follow-up visit was scheduled, with improvement of the hyperpigmented skin lesions (Figure 3). Paresthesia of both legs were still present, probably due to CKD.

Figure 3 Improvement of hyperpigmented skin lesions four weeks after thermal stimulus withdrawal.

Acknowledgments

Funding: None.

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