Coexistence of psoriasis and bullous pemphigoid in three cases

Psoriasis vulgaris and bullous pemphigoid represent 2 clinically and histologically distinct, chronic inflammatory skin conditions. The concomitant occurrence of these 2 diseases is rare, and the pathogenic relationship between psoriasis and bullous pemphigoid remains unclear. The development of bullous pemphigoid in patients with psoriasis is considered to be related to treatments for psoriasis, especially ultraviolet therapy. However, some recent reports have suggested that an immunologic or biochemical association between these two diseases plays a role in the pathogenesis. Herein, we report 3 cases of bullous pemphigoid occurring in patients with psoriasis, and we discuss the possible pathogenic mechanisms of an association between psoriasis and bullous pemphigoid.