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
[{'content': 'An auto immune disease is: \nSelect and explain. \nA. Pemphigus Vulgaris, B. Psoriasis, C. Lichen Planus, D. Acne Vulgaris', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Pemphigus vulgarisDiseaseEtiologyPemphigusPemphigoid, Epidermolysis bullosa acquisitaAutoinimune(2Lichen planusInflamatory disorder of unknown originAcne vulgarisObstruction of pilo-sebaceous gland.QEpidermolysis bullosa congenitaPsoriasisGenetic diseaseQ of unknown originGenetic dsQ unknown (inflamatory) origin', 'role': 'assistant'}]