The correct answer is B. Perivascular IgA deposition.
The associated image depicts the classic “palpable purpura” of cutaneous small-vessel vasculitis (CSVV). A specific type of CSVV now known as IgA vasculitis (formerly Henoch-Schonlein Purpura) typicallt presents with palpable purpura on the lower extremities and buttocks, along with arthritis, hematuria, colicky abdominal pain +/- GI bleeding and vomiting. A biopsy for H&E reveals leukocytoclastic vasculitis, and a biopsy for DIF shows perivascular IgA, C3, and fibrin. Treatment is mainly supportive as it is typically self-limited.
Dermatitis herpetiformis – IgA deposition in the dermal papillae. Linear IgA bullous disease/chronic bullous disease of childhood – Linear IgA deposition along the basement membrane zone. Bullous pemphigoid – Linear IgG (and C3) deposition along the basement membrane zone.