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
A 30-year-old male had severely itchy papulo–vesicular lesions on extremities, knees, elbows and buttocks for one year. Immunofluorescence staining of the lesions showed IgA deposition at dermo-epidermal junction. The most probable diagnosis is – 
Select and explain. 
A. Pemphigus vulgaris, B. Bullous pemphigoid, C. Dermatitis herpetiforms, D. Nummular eczema
C: Dermatitis herpetiforms
Answer: C: Dermatitis herpetiforms 
Explanation: Itchy papulovesicular lesions on extensor surfaces and deposition of IgA at DEJ suggests the diagnosis of dermatitis herpatiformis, which is associated with Coeliac disease