52-year-old male presents to the family medicine office for follow-up in regards to a blister that was treated on his right arm two weeks ago...

A 52-year-old male presents to the family medicine office for follow-up in regards to a blister that was treated on his right arm two weeks ago. He has completed his course of ciprofloxacin, as prescribed, with little to no improvement. During the last two weeks, a similar rash has appeared on his right forearm. He denies any travel, trauma, new hygiene products, or insect bites. The patient states he has had no fever or chills, GI symptoms, joint pain, or numbness. Physical examination of his extremity reveals a large erythematous patch with clusters of hemorrhagic vesicles and bullae as shown in the exhibit. There is no inguinal lymphadenopathy or mucosal involvement. Nikolsky sign is negative.

The most likely diagnosis is?

A. bullous pemphigoid
B. dermatitis herpetiformis
C. erythema multiforme
D. pemphigus vulgaris
E. porphyria cutanea tarda

Laboratory evaluation will most likely reveal?

A. acantholysis
B. decreased uroporphyrinogen decarboxylase
C. hemidesmosomal autoantibodies
D. increased lymphocytes and necrotic keratinocytes
E. positive antistreptolysin O titer

The best course of treatment for this patient is?

A. phlebotomy
B. phototherapy
C. potassium iodide
D. rituximab
E. topical corticosteroids