An 82-year-old man presents with a 1 and a half-week history of severe pruritus and eczema. His past medical history includes atopic dermatitis, thyroid disease, and multiple sclerosis. On physical examination, he has dozens of 1-2 cm tense bullae and several erosions over his upper and lower extremities. His oral mucosa is not involved. Nikolsky sign is negative. A skin biopsy is taken and anti-BP 180 is detected in his blood. A potent topical steroid is prescribed. The most likely diagnosis is
Pemphigus vulgaris
Bullous pemphigoid
Necrotising pemphigus
Contact ezema
Ans. is 'b' Bullous Pemphigoid Pemphigoid is commonly seen in old age (60-80 yrs) as bullous eruptions on lower limb. Both pemphigus and pemphigoid give bullous lesions but they differ in other characteristic. Pemphigus Pemphigoid Nikolsky sign present* Bullae are intraepidermal & flaccid* Mucosa involved* Acantholysis present* Involves upper part of body Age of involvement 40-60 yrs* Prognosis poor Nikolsky sign absent Bullae are supepidermal & tense Mucosa not involved Acantholysis absent Involved lower part of body. Age of involvement 60-80 yrs* Prognosis Good