A new blistering disease in an older person is typically going to be a pemphigus question. Then you just have to remember the difference between bullous pemphigoid vs pemphigus vulgaris. Bullous pemphigoid is characterized by the loss of hemidesmosomes that bind keratinocytes to the basement membrane, resulting in bulla (big blisters) in areas of friction (Choice A). Patients with pemphigus vulgaris lose their desmosomes (which bind keratinocytes to each other), so that their skin is super friable, which results in ulceration. Mouth ulcers are more common in PV.