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 30 year old male had severely itchy papula-vesicular lesions on both knees, elbows, upper back and buttocks for one year. Direct immunofluorescence staining of the lesions showed IgA deposition at dermoepidermal junction and dermal papilla. The most probable diagnosis is : 
Select and explain. 
A. Pemphigus vulagris, B. Bullous pemphigoid, C. Dermatitis herpetiforms, D. Nummular eczema
C: Dermatitis herpetiforms
Answer: C: Dermatitis herpetiforms 
Explanation: C i.e. Dermatitis herpetiformis