**4. Criteria for the diagnosis of SJS/TEN based on extent of epidermal detachment**

Steven Johnson Syndrome is an immune complex-mediated hypersensitivity reaction that involves mucocutaneous body areas such as oral, nasal, ocular, vaginal, urethral, gastrointestinal, and lower respiratory tract mucous membranes. Moreover, gastrointestinal and lower respiratory tract infections may progress to necrosis. The diagnosis of steven johnson syndrome, Toxic epidermal necrolysis, or overlap syndrome totally depends on the afflicted skin body surface area with epidermal detachment (**Figure 3**) [21].

#### **Figure 3.**

*The extent of epidermal detachment in SJS/TEN. (adapted from fig 21.9 Bolognia and Bastuji-Garin S. et al. arch Derm 129: 92, 1993).*


*Abbreviations: BSA- Body Surface Area, EM- Erythema Multiforme, SJS- Steven Johnson Syndrome, TEN - toxic epidermal necrolysis. Adapted from Bastuji-Garin S et al. Clinical classification of cases of toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme. Arch Dermatol 1993; 129(1): 92–96 (adapted from Bastuji-Garin S et al.).*

#### **Table 2.**

*Distinguishing features of different severe bullous skin lesions.*


Distinguishing features of different severe bullous skin lesions are tabulated below (**Table 2**) [22].
