This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blistering disorders, Subject name: Dental
[{'content': 'A 30-yr-old male had severely itchy papulovesicular lesions over the extremities, knees, elbows and buttocks for one year. Direct immunofluorescence staining of lesions showed IgA deposition in papillary dermis in granular pattern . The most probable diagnosis is: \nSelect and explain. \nA. Pemphigus vulgaris, B. Bullous pemphigoid, C. Dermatitis herpetiformis, D. Nummular eczema', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Dermatitis herpetiformis C/F : Itchy papulovesicular lesions of the extremities, knees, elbows and buttocks. DIF : IgA deposition at papillary dermis in granular pattern known as picket fence appearance.', 'role': 'assistant'}]