Perforating folliculitis and psoriasis

A 51-year-old man with a 10-year history of psoriasis presented with coexistent perforating folliculitis. Several perforating lesions were located within psoriatic plaques. This case is instructive from several viewpoints: (1) it is the second case to appear in the literature, to our knowledge, describing the coexistence of these two conditions; (2) several of the larger lesions resolved during topical therapy with retinoic acid; (3) it demonstrates the histologic difficulties encountered in attempting to classify the major perforating diseases. Possible mechanisms for the development of perforating disease in this patient are discussed, as are the reasons for its apparent response to topical therapy.