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: Dental
[{'content': 'An autoimmune disease is – a) Pemphigus vulgarisb) Psoriasisc) Lichen planusd) Acne vulgaris \nSelect and explain. \nA. abc, B. bc, C. acd, D. bcd', 'role': 'user'}, {'content': "Answer: A \nExplanation: Autoimmune skin disorders\n\nAutoimmune bullous skin disorders\n\n\nPemphigus\nBullous pemphigoid\nDermatitis herpetiformis\n\nLichen planus\n\nLichen planus is believed to be an autoimmune disorder as it often occurs concurrently with other autoimmune\xa0disorders like primary biliary cirrhosis, diabetes, chronic active hepatitis.\n\nPsoriasis\n\n\xa0The theory that psoriasis is an autoimmune disorder is based on the fact that scientist have found an abnormally\xa0large number of T cells in the patch of psoriasis.\n\nAutoimmune connective tissue disorders\n\nLupus erythematosus\nDermatomyositis\nScleroderma\nMixed connective tissue disease\nBechet's disease", 'role': 'assistant'}]