Unilateral psoriasis: a case individualized by means of involucrin.

Several authors have questioned the existence of unilateral (linear) psoriasis. These authors have suggested that the condition is actually an inflammatory linear verrucous epidermal nevus, or the result of an isomorphic effect on a pre-existing epidermal nevus. We report the case of a 25-year-old man, with no relevant personal or family history, who presented with a number of pruritic, punctiform erythematosquamous lesions that were linearly distributed over the left side of the body. Clinical examination and results of histopathologic and histochemical studies indicated unilateral psoriasis. Our findings confirm that involucrin immunohistochemistry can be a useful diagnostic tool in cases of this type. Treatment with keratolytics and topical calcipotriol led to a significant, but only temporary, improvement.