Porokeratosis is a disorder of keratinization characterized by a distinct peripheral, thin, ridge-like scale that corresponds histologically to a thin, angled column of epidermal parakeratotic cells that extends through the stratum corneum. Disseminated superficial actinic porokeratosis (DSAP) is a very common form of porokeratosis. The lesions are minimally elevated keratotic papules symmetrically distributed on sun-exposed sites. Patients with DSAP may complain of exacerbations during the summer months with increased pruritus or burning sensation.

DSAP is thought to have autosomal dominant inheritance with onset in the third or fourth decade of life. Women are affected 3 times more frequently than men. Risk factors for developing this disorder also include exposure to ultraviolet radiation and immunosuppression. Individuals with light skin phototypes are more prone to developing this disorder. Recently, mutations in the mevalonate kinase pathway have been identified in DSAP and are thought to be the pathogenetic basis of this disorder.

The potential for transformation to squamous cell carcinoma (SCC) exists but is rare.