Pemphigus vulgaris is an autoimmune blistering disease that affects the skin and mucous membranes. It is caused by autoantibodies that attack desmoglein, a protein that binds epidermal cells together. This causes the epidermal cells to separate from each other (acantholysis) and form fragile blisters that rupture easily, leaving painful erosions. Pemphigus vulgaris is diagnosed through skin biopsy and detection of anti-desmoglein antibodies. Without treatment, it can be fatal due to infection; treatment involves high-dose corticosteroids and other immunosuppressants to control outbreaks and lessen side effects.