Erythema multiforme

Erythema multiforme is a skin condition that causes distinctive red, target-shaped or bullseye-like lesions. It primarily affects the skin and sometimes the mucous membranes, such as the mouth and eyes. The condition is often triggered by infections, especially with the herpes simplex virus, or by certain medications. These skin changes can be uncomfortable and may be accompanied by itching or burning sensations. Although it can look alarming, it usually resolves on its own or with treatment. The main health impact is on the skin's appearance and comfort, but severe cases can affect eating or vision if mucous membranes are involved.

Erythema multiforme is an acute, immune-mediated hypersensitivity reaction characterized by the sudden onset of distinctive target lesions on the skin and sometimes mucous membranes. It is most commonly triggered by infections, particularly herpes simplex virus, or less commonly by medications. The pathogenesis involves a cell-mediated immune response targeting keratinocytes expressing foreign antigens, leading to epidermal necrosis and inflammation. Clinically, it presents with symmetric, round, erythematous macules that evolve into classic target lesions with three zones: a central dusky area, a pale edematous zone, and an outer erythematous ring. The condition is classified into minor and major forms, with major involving mucosal surfaces and systemic symptoms. It is important to distinguish it from Stevens-Johnson syndrome and toxic epidermal necrolysis, which are more severe mucocutaneous reactions.