Another common cutaneous eruption seen during the colder months of the year is that of erythema ab igne.
In contrast to chilblains, this is a condition caused by excessive exposure to heat in the form of infra-red radiation. This can be from a hot water bottle through to the heat of a notebook computer.
The immediate consequences are those of erythema in a livedoid pattern.
Livedo refers to a net-like structure. In extreme cases, this may become blistered. The erythema subsequently becomes hyperpigmented. Symptoms can range from none through to itch and mild discomfort.
The main long term problem, aside from the hyperpigmentation, is that of an increased risk of various skin malignancies such as squamous cell carcinomas.
Histopathologically, features usually seen in sun damaged skin are found in areas of erythema ab igne.
Heat is often applied to relieve localised chronic pain, especially in the form of a water bottle. It is always important to ensure that there is no serious underlying cause for such pain. There have been instances of erythema ab igne affecting the back in patients with pancreatic carcinoma.
When there is no history of heat exposure, it is especially important to consider other causes of livedo: in particular, vasculitis (polyarteritis nodosa), thrombophilic disorders, and connective tissue diseases such as lupus.
Although livedo can occur physiologically due to cold exposure, this is transient. The more serious forms of livedo are usually more extensive (Figure 1), and often form an irregular net-like pattern rather than the regular network formed by physiological livedo reticularis. This is sometimes referred to as livedo racemosa, and is an indication for more aggressive investigation including biopsy.
Of note, when doing a biopsy of an area of livedo, it is usually best to biopsy the central pale area rather than the hyperaemic edges, as this is where the diseased central feeding blood vessel is likely to lie.
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