Bullous Pemphigoid in Which Eruption Developed Exclusively on Preexisting Eruption of Vitiligo Vulgaris

Coexistence of bullous pemphigoid (BP) and vitiligo vulgaris (VV) is very rare. We present a unique case of BP associated with VV in a 76-year-old Japanese man, in which BP eruption developed exclusively on preexisting VV regions. The patient was referred to us with a 3-month history of blistering eruption with severe pruritis on the right forearm and left lower limb. In addition, he had been suffering from a widespread depigmented eruption on the trunk and extremities for at least 20 years. Curiously, the blistering eruption developed exclusively on preexisting depigmented eruption. Histopathological and laboratory examinations identified the blistering eruption as BP. The depigmented eruption was diagnosed as VV. BP eruption responded quickly to oral prednisolone therapy, improving within 1 week, and the prednisolone dose was gradually tapered. Within 1 month, BP lesions almost completely resolved. In the present case, BP not only coexisted with VV, but also developed exclusively on preexisting vitiliginous regions. The present case strongly suggests that BP and VV are partly caused by common pathological mechanisms.