Erythema Multiforme (EM), Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) exist on a spectrum but vary considerably with regard to presentation and underlying etiologies. Here are some clinical pearls to help conceptualize these fascinated pathologies.
|Morphology||Typical three-zoned target||Atypical targets and confluent erythema with sloughing||Extensive, confluent erythema with sloughing|
|Distribution||Favors extremities||Trunk, extremities
Up to 10% BSA involvementa
At least 30% BSA involvementa
|Mucosal disease (oral, eye, genitourinary)||One or two sites||Two or more sites||Two or more sites|
|Caused by infection (%) (herpes simplex orMycoplasma pneumoniae)||30-80||22||6|
|Caused by drugs implicated in (%)||Up to 50||74||94|