This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
A 40 year old male developed persistant oral ulcers followed by multiple flaccid bullae on trunk and extremities. Direct immunofluorescence examination of a skin biopsy showed intercellular IgG deposits in the epidermis. The most probable diagnosis is: 
Select and explain. 
A. Pemphigus vulgaris, B. Bullous Pemphigoid, C. Bullous Lupus erythematosus, D. Epidermolysis bullosa acquisita
A: Pemphigus vulgaris
Answer: A: Pemphigus vulgaris 
Explanation: It is an autoimmune intraepidermal blistering disease due to antibodies against desmoglein 3. It begins as painful oral erosions followed by flaccid blisters on the trunk, face, scalp. Ref: Current Literature Dermatology By Pasricha, Pages 197, 202; Rook's Textbook of Dermatology, 8th Edition.