Pemphigus is an autoimmune blistering disease characterized by autoantibodies against epidermal adhesion molecules, desmogleins. Pemphigus vulgaris is most common and shows intraepidermal vesicles caused by the breaking apart of epidermal cells, acantholysis. A 65 years old male patient complained of severe mucosa ulceration on his right mandibular retromolar pad area where traumatic injuries occurred during mastication. He also had multifocal round skin ulcerations, less than 7~8mm in diameter and showed habitual onset and disappeared soon. At this time he was anxious about his oral ulceration with a cancer phobia, thereby a biopsy was made to rule out any malignancy in the ulceration. The histology examination showed multifocal suprabasal splits forming vesicles and erosion. The suprabasal splits were linear and parallel to the basal cell layer. The immunostain of IgK was strongly positive in the vesicular fluid as well as the cell membranes of dissociating keratinocytes, and also positive in many plasma cells infiltrated into the subepithelial zone. TNFα, IL‐1, ‐8, ‐28 for the pro‐inflammatory reaction were weakly expressed, while IL‐6 was strongly positive in the acantholytic keratinocytes of vesicle forming area. β‐defensin‐1, ‐2, ‐3 for the innate immunity were diffusely positive in the involved epithelium. The cell survival proteins, pAKT and HSP‐70 were diffusely positive in the epithelium, while the apoptosis protein, PARP was consistently positive in some acantholytic keratinocytes. These findings indicated that the vesicle formation occurred by autoantibody reaction without the activation of pro‐inflammatory and cell‐mediated immune reactions. The lesion was diagnosed pemphigus vulgaris with abrupt onset of epithelial vesicles at the predisposing areas of traumatic injuries by type II hypersenstitive immune reaction.