Diagnosis of SJS/TEN
Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe mucocutaneous reactions. They are most commonly triggered by medications and characterized by extensive necrosis and cleavage of the epidermis from the dermis akin to a superficial or partial thickness burn.
According to a widely accepted classification, SJS and TEN are considered a disease continuum and are distinguished chiefly by severity, based upon the percentage of TBSA affected by blisters and erosions:
SJS is the less severe condition, in which skin detachment is <10% of the TBSA.
TEN involves detachment of >30% percent of the TBSA.
SJS/TEN overlap describes patients with skin detachment of 10 to 30% TBSA.
In medical notes, literature, and this document, SJS/TEN is used not only to describe 10 to 30% TBSA but as a general descriptor of SJS, TEN, or SJS/TEN. Toxic epidermal necrolysis destroys the epidermis but also may involve the upper dermis as they are connected to one another.
Mucosal involvement (erythema and erosion) occurs in 90% of cases and can precede skin eruption by 1 to 3 days. The oropharynx, eye, and genitalia are the most frequently affected mucosal membranes. The urethra is also a mucus membrane. Other mucus membranes have been reported, including the respiratory tract and gastrointestinal tract.
By contrast, deeper burns/full thickness burns can destroy skin down to the subcutaneous fat. This can also destroy blood vessels and nerves. Full-thickness burns are painless, as opposed to superficial or partial-thickness burns which are painful. However, full-thickness burns do not blister; if blisters are large, they are classified as bullae.
The diagnosis of SJS/TEN is considered when there are some or all of the following:
A suggestive history of drug exposure or febrile illness.
A painful rash that progresses rapidly.
Erythematous macules, targetoid lesions, or diffuse erythema progressing to vesicles and bullae.
Positive Nikolsky sign.
Oral, ocular, and/or genital mucositis with painful mucosal erosions.
Necrosis and sloughing of the epidermis of varying degree.