Cutaneous horn and thermal keratosis in erythema AB igne

Apra Sood, Sandeep Sharma, Neena Khanna

 Department of Dermatology and Venereology, All India Institute of Medical Sciences, New Delhi 110 029, India

Correspondence Address:
Neena Khanna
Department of Dermatology and Venereology, All India Institute of Medical Sciences, New Delhi 110 029
India

Introduction

Actinic keratoses occur in sun-exposed skin due to an epidermal change which manifests as adherent scales. A similar change may be induced by radiant heat.[1] The scale in the keratoses may become thick and raised but the development of a cutaneous horn is uncommon. We report a 46-year-old lady who developed multiple keratoses and a cutaneous horn in a background of erythema ab igne.

Case Report

A 46- year-old Kashmiri lady complained of developing blotchy erythema on the medial aspects of both legs during the winter season for the past 15 years. She had a habit of sitting close to coal fire during every winter for the past 30 years. The erythema improved during the initial summers but later persisted throughout the year. Five years ago, she started getting mildly itchy adherent scales on the same area. The lesions gradually increased in number. Three years later, she noticed a thick hard projection from the lesion on the left leg. At the time of presentation, she had symmetrical reticulate hyperpigmentation, telangiectasias and mild atrophy on the medial and anterior aspects of both legs. There were multiple brownish and adherent scales scattered on the involved skin; on removal of scales, bleeding points were revealed. She had a painless hard hyperpigmented horny growth projecting from a lesion on the left leg [Figure - 1]. The base of the cutaneous horn was neither indurated nor inflamed. There was no other skin or mucus membrane lesion. A routine hemogram, liver and renal function tests were within normal limits. A histopathological examination of the excised cutaneous horn showed marked hyperkeratosis, acanthosis and a mild lymphocytic infiltrate in the dermis. A biopsy from the keratosis revealed hyperkeratosis, parakeratosis, irregular acanthosis and a marked lymphohistiocytic infiltrate around the dermal vessels. The patient was advised to strictly avoid sitting close to a source of radiant heat. She was given emollients for topical application and is under follow - up.

Discussion

Erythema ab igne results from a repeated, chronic exposure to infrared radiation. It is seen frequently in people from cold climates who sit close to fires or frequently use hot water bottles. In long standing cases the skin becomes poikilodermatous with reticulate pigmentation and atrophy. The pattern of erythema ab igne depends on the direction of the radiation and the contour of the skin. In our patient, a symmetrical eruption was seen due to a habit of sitting directly in front of the fire. The histopathological changes resemble those induced by actinic damage[2] and keratosis may form, although infrequently. As keratosis has a low - grade malignant potential, they should be observed closely and any induration at the bases should be viewed with suspicion.

Although we see patients with erythema ab igne, development of keratosis and a cutaneous horn in the affected skin is not a frequent observation. Cutaneous horn is an outgrowth of keratin due to retention of stratum corneum often seen in a variety of primary diseases of benign and malignant nature.[1],[4] In thermal keratosis, the dysplastic epidermal changes may result in the formation of a horn. In such a clinical situation the cutaneous horn should be observed for inflammation and induration at the base which is suggestive of a malignant transformation. Histopathologically, if there is a budding from the basal layer, it signifies transition into a squamous cell carcinoma. In a patient like ours, it is imperative to stop exposure to radiant heat to prevent further damage to the skin and to reduce the risk of malignant transformation.

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