Disseminated porokeratosis in immunosuppressed patients.

More than a century ago, two Italian dermatologists independently described a new keratotic disorder [1,2] which was called porokeratosis by Mibelli [1]. After these first descriptions, at least four variants of porokeratosis have been recognized. Clinically all these dermatological disorders are characterized by diffuse annular lesions surrounded by a raised, sharply marginated, keratotic border. The typical histological feature is represented by the cornoid lamella, which is a column of parakeratotic cells. The most common form is the disseminated superficial porokeratosis, characterized by diffuse small lesions, generally distributed over the legs, more rarely also on the buttocks and the arms. Idiopathic disseminated porokeratosis affects both males and females, usually around the 5th decade. The disease is transmitted as an autosomal dominant trait with variable penetrance. It has been hypothesized that porokeratosis may be triggered by a proliferation of abnormal clones of epidermal cells in response to several stimuli, the most important of which are sunlight and artificial UV [3].