A 30-year-old woman develops a pruritic vesicular eruption on her earlobes two days after wearing new earrings. Skin biopsy shows a perivascular lymphocytic infiltrate with spongiosis. Which hypersensitivity mechanism underlies this lesion?

• A IgE-mediated mast cell degranulation
• B Complement-mediated lysis of keratinocytes by IgG antibodies
• C Immune complex deposition in dermal vessels
• D CD4+ T cell mediated delayed response to a hapten-carrier complex ✓

Explanation

Allergic contact dermatitis is a Type IV reaction in which small chemicals such as nickel act as haptens, bind skin proteins, and are presented by Langerhans cells to CD4+ T cells, producing a delayed eczematous response peaking at 48 to 72 hours. The delay and the lymphocytic infiltrate exclude IgE mast cell mechanisms, which cause immediate wheal-and-flare reactions within minutes.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.