Race for the Case

A 20-year-old female with no significant past medical history presented to the hospital with a one-week history of a diffuse blistering rash. One week prior to onset, the patient reports she took a pain reliever for headache relief. She denied any fever, arthralgias,edema, eye pain, throat pain, urinary issues, or abdominal discomfort. During her hospital stay, she had no laboratory abnormalities and her vital signs were within normal limits. On physical exam, no lymphadenopathy, peripheral edema, or joint tenderness was noted. Over her back, shoulders, arms, legs, chest, and face there were several erythematous annular plaques with surrounding tense vesicles in a “crown of jewels” arrangement and bullae with associated erosions and crust. No involvement of the palms, soles, or mucous membranes were noted. Biopsy showed a subepidermal blister with neutrophils and a perivascular infiltrate. Direct immunofluorescence demonstrated IgA (immunoglobulin A) and C3 (complement component 3) in a linear pattern along the basement membrane zone.

1. What is the diagnosis?
2. In drug-induced cases, what is the most common culprit?
3. What is the treatment of choice and what laboratory study must be ordered prior to initiation?
4. What are the two antibody targets in this condition?
5. What is on the differential diagnosis?