Porokeratosis (PK) is a rare skin disease, of unknown etiology, probably due to a disorder of epidermal keratinization. We describe a 24 year-old male patient, with porokeratosis of Mibelli confirmed histopathologically.

A 24-year-old man, a farmer by profession, without pathological history, consulted for a papular, rounded, slightly squamous lesion. Measured 0.5 cm in diameter, with raised border and depressed squamous center. This lesion is on left wing of the nose (Figure 1). This lesion evolved asymptomatically for 4 years.

Figure 1: Keratosic lesion on the nose.

The discussed diagnostics were discoid lupus, basocellular carcinoma, bowen disease and porokeratosis of Mibelli. A skin biopsy showed the presence of the coronoid lamella (Figure 2) confirming the diagnosis of porokeratosis of Mibelli. A local treatment by retinoid was administered but it was suspensif. Cryotherapy has been a great success without recurrent lesion after 24 month.

Figure 2: Cornoid lamella.

PK was first described and named so by Mibelli in 1893, but still the etiology of PK is unclear [1]. Clinically, characterized by annular plaques with an atrophic center with hyperkeratotic edges [2]. It includes a heterogeneous group of disorders that are mostly inherited in an autosomal dominant form [1]. We can describe many types (Porokeratosis of mibelli, linear porokeratosis, punctuate keratosis, palmoplantar leratosis) [3]. But histologically, they all have in common the presence of a cornoid lamella [1]. This desease may be associated with immunosuppression (leukemia, organ transplant) and may undergo malignant transformation [4].

Cryotherapy is effective in the treatment of individual symptomatic lesions of porokeratosis. Oral and topical retinoid has also been successfully used in the treatment of disseminated porokeratosis of Mibelli [5].