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
A 24 yr-old female has flaccid bullae over the skin and oral erosions. Histopathology shows intraepidermal blister with acantholytic cells. Diagnosis is: 
Select and explain. 
A. Pemphigoid, B. Erythema multiforme, C. Pemphigus vulgaris, D. Dermatitis herpetiformis
C: Pemphigus vulgaris
Answer: C: Pemphigus vulgaris 
Explanation: The features of intaepidermal acantholytic blisters coupled with flacid bullae over skin and oral erosions points towards P. vulgaris. The other 3 diseases do now show intraepidermal blistering. They are devoid of mucosal involement. Erythema Multiforme: Target lesion seen on distal extremeties. If mucosa involved it is called as Epidermal Multiforme Major Dermatitis herpetiformis: Extremely pruritic vesicopapules over extensors Pemphigoid: Tense bullae