EM represents a syndrome of inflammatory skin eruptions that can manifest as a mild self-limiting form or as a life-threatening condition requiring aggressive lifesaving and critical care therapies.

EM-minor, or the mild form of EM, is characterized by the occurrence of characteristic skin lesions, which are described as target lesions, iris lesions, or iris erythema. The skin lesions follow a symmetric distribution and commonly seen on the extensor surfaces of the extremities, back of hands, feet, palms, and soles. The trunk and head are usually spared. Cutaneous symptoms consist of itching, stinging, and burning sensations; occasionally, general symptoms, such as mild fever and chill, are present.

The “erythema multiforme disease spectrum” comprises four distinct, severe, clinical subvariants: (a) bullous erythema multiforme (bullous-EM), (b) SJS, (c) SJS–toxic epidermal necrolysis (TEN)-overlap syndrome, and (d) TEN.

EM-major or bullous EM, in addition to the characteristic target lesions in symmetric distribution, consists of atypical, raised target lesions with some degree of moderate epidermal detachment involving <10% of the body surface.

In SJS, the cutaneous lesions are more extensive, with flat-atypical targets and macules that predominate over classic target lesions, and predominately in the trunk and face. When epidermal necrolysis becomes a dominant feature, with involvement of up to 10% of the body surface, EM-major merges into SJS. Blistering of individual skin lesions as well as erosions/detachment become delineating features. Moreover, these patients develop severe and extensive mucosal lesions of the oral, conjunctival, and genital mucous membranes, which then determine the course of the disease. These lesions are painful and consist of desquamation, erosions, and superficial ulcerations. This disease is often complicated by extensive percutaneous
loss of electrolytes and fluids, and there is a high risk for scarring and milia and synechia formation, especially on the eyes, upper gastrointestinal tract, trachea, and genitalia. Patients are also at risk of serious bacterial infections from their erosions.