Derm

Question 1

Pathogenesis of Erythema multiforme

Answer 1

This occurs when circulating pathogens are phagocytosed by peripheral mononuclear cells and are brought to the epidermis, where DNA fragments are transferred to keratinocytes via direct cell-to-cell spread (facilitated by upregulation of adhesion molecules).

Pathogen specific T cells then recognize foreign antigens produced by keratinocytes and initiate an inflammatory cascade that results in epithelial damage.