Erythema multiforme is best described as which type of hypersensitivity reaction?

Erythema multiforme is best described as which type of hypersensitivity reaction?

• A. Type IV hypersensitivity reaction
• B. Type II hypersensitivity reaction
• C. Type I hypersensitivity reaction
• D. Type III hypersensitivity reaction

Answer: (A)

Erythema multiforme is driven by a cell-mediated, delayed-type immune response. Sensitized CD8+ T cells attack keratinocytes in the skin (often triggered by a herpes simplex infection or certain drugs), releasing cytotoxic mediators that induce keratinocyte apoptosis. This T-cell–mediated process classifies it as a Type IV hypersensitivity reaction. The damage arises from immune cells rather than antibodies or immune complexes, which is why it isn’t Type I, II, or III.

Erythema multiforme is driven by a cell-mediated, delayed-type immune response. Sensitized CD8+ T cells attack keratinocytes in the skin (often triggered by a herpes simplex infection or certain drugs), releasing cytotoxic mediators that induce keratinocyte apoptosis. This T-cell–mediated process classifies it as a Type IV hypersensitivity reaction. The damage arises from immune cells rather than antibodies or immune complexes, which is why it isn’t Type I, II, or III.