funny i got pimped on this question on my first day of electives
EM has NOTHING to do with SJS or TEN, it is not a mucosal disease inovled primarily with HSV as the major cause of eruptions, then far far after that you have drug eruptions
SJS and TEN are primarily caused by drug eruptions but have also been known to be caused by mycoplasma infections as well, however SJS/TEN differe from EM because they involve the mucosa,
books say SJS differs from EM because it involves at least 10% of the body or 2 mucosal surfaces, mouth, anal, or orbital mucosa
TEN is a an extension of SJS and is d/t extensive tissue distruction beyond bullae vesicles and crusts, it is indeed epidermal necrolysis
