Erythema ab igne, also known as dermatitis ab igne, is a persistent telangiectatic reticular erythema caused by repeated exposures of the local skin to high temperature insufficient to cause burns.
Long term, repeated exposures to high temperature are the causes.
Signs and Symptoms
The skin of the anterolateral calves is congested due to the heat radiation when persons sit in front of the fire in winter, forming reticular erythema. Subsequently, the erythema gradually develops from light red to purplish red and purplish brown, forming reticular hyperpigmentation. The skin lesions gradually subside when the weather turns warm. Patients in the hotbed or individuals who have hot compress with rubber hot water bottles are susceptible to the condition.
Figure 1 erythema ab igne
In the high-temperature workshops of ironworks and glass factories, workers have long been exposed to hot irritation. The face, buttocks, and chest can be swollen and desquamated, and finally the skin swells, presenting persistent, reddish brown erythema caloricum.
There are mild hyperkeratosis, sometimes accompanied by the thickened granular layer or dyskeratosis, epidermal atrophy with vacuolar degeneration of spinous cells, and occasionally heteromorphic nuclei. Vasodilation in the papillary dermis and mixed cell infiltration around the blood vessels can be seen. The connective tissue of the reticular dermis can be changed, and the elastic fibers may be enlarged and thickened. Hyperpigmentation is caused by the infiltration of melanophages, free melanin granules, and hemosiderin in the dermis.
If there are a history of long term exposure to high temperature and clinical presentations, the disease can be diagnosed.
The early skin lesions can heal spontaneously. The persistent hyperpigmentation can be treated by decolorizing agents such as 3% - 5% hydroquinone cream, superoxide dismutase (SOD) cream, and 0.05% - 0.1% tretinoin ointment. Atrophic lesions are mostly permanent. Hyperkeratosis can be treated by topical fluorouracil ointment or surgical resection.