Erythema ab igne

Erythema ab igne (EAI) is characterised by localised areas of reticulated (net-like) erythema and hyperpigmentation caused by chronic exposure to infrared radiation in the form of heat. It was once a common condition seen in the elderly who sat close to open fires. Although the introduction of central heating has reduced EAI, it is still found in individuals exposed to heat from other sources.

This chapter is set out as follows:

• EAI is caused by prolonged and repeated exposure to a level of heat insufficient to cause a direct burn

• Some patients complain of mild itch or a burning sensation

• The initial presentation is a transient macular erythema arranged in a broad, reticulated (net-like) pattern that easily blanches
• With prolonged and repeated exposure, areas of reticular erythema persist and, in time, become livid and hyperpigmented
• The entire size and shape of the lesion often approximates that of the heat source
• The skin and underlying tissue may start to thin, rarely sores develop
• In patients with severe long-standing EAI, poikilodermatous changes may result

• The source of chronic heat exposure must be avoided. If the skin changes are only mild they are likely to resolve over several months. If the skin changes are more severe they are likely to persist

• There appears to be a small long-term risk of squamous cell carcinoma or Merkel cell carcinoma developing in areas of EAI - the latent period may be 30 years or more. As such, enlarging skin lesions or persisting areas of ulceration within an area of EAI should be referred urgently