Porokeratosis is a hereditary disorder of keratinization. It manifests clinically by the presence of annular plaques with hyperkeratotic borders, mostly in acral regions. The characteristic histologic finding is a compact parakeratotic column called the cornoid lamella.

This image is from a 64-year-old man with no past history of interest. He presented multiple desquamating annular erythematous lesions with well-defined hyperkeratotic borders that had arisen 3 years earlier on his lower limbs (Fig. 1). The clinical diagnosis of disseminated superficial actinic porokeratosis was confirmed histologically by the presence of cornoid lamellae. The lesions in this patient are particularly striking, given their prominent, very well-defined borders and the large number of lesions showing the same morphology (Fig. 2). The patient had used numerous topical treatments with no improvement, and it was therefore decided to start low-dose oral ciclosporin, which achieved a good response and improvement of the lesions.

Figure 1

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Figure 2

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