Lichen simplex chronicus with a cutaneous horn.

A 55-year-old male developed itching on the anterior aspects of both legs and the right ankle. Gradually over the next 5 years there was thickening of the skin on these areas followed by the appearance of hyperpigmented, scaly, severely itchy plaques. He also noticed the appearance of a thick, hard horn-like structure projecting from the surface of the right ankle lesion for the last 2 years. At the time of presentation there were multiple hyperpigmented, irregular scaly licheni¢ed ill-de¢ned plaques ranging from 2 to 4 cm in diameter on the anterior aspects of both legs and the right ankle. The lesions on the right ankle had an outwardly projecting hard hyperpigmented, non-tender horny growth about 0.5 cm in diameter at its base and of almost the same length (Fig. 1). There was no other skin or mucous membrane lesion. Routine haemogram, liver and renal function tests were within normal limits. We made a diagnosis of lichen simplex chronicus with a cutaneous horn. Histopathological examination of the excised cutaneous horn showed marked hyperkeratosis and acanthosis with scattered lymphocytes in the upper dermis. The surrounding lesion showed hyperkeratosis, keratotic plugging, acanthosis and papillomatosis and focal chronic in£ammation in the upper dermis. These features were consistent with a cutaneous horn in the lesion of lichen simplex chronicus. The patient was treated with 0.05% clobetasol propionate cream topically twice daily. The skin lesions had responded satisfactorily by the end of 4 weeks of treatment.