Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis

Background

Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are severe skin reactions (usually to medications) that constitute dermatologic emergencies
- Common culprit medications: antibiotics, anti-epileptic drugs, NSAIDs
SJS and TEN are the along the same disease spectrum, TEN is just clinically more severe and widespread
- The extent of epidermal detachment is <10% total body surface area (tBSA) in SJS and >30% tBSA in TEN
This is a rare disease (1 case per million per year), but is more common in patients with HIV/autoimmune disorders/immunosuppression and the elderly (likely because of this population's increased use of medications).
- Certain genetic markers are associated, especially HLA markers.
- In bone marrow transplant patients, TEN can be indistinguishable from acute graft vs host disease
The mechanism is thought to be the host's inability to metabolize the offending drug, which results in toxic metabolite buildup, which then activates T cells and keratinocyte apoptosis.

Typically occurs 4 days to 4 weeks after the drug exposure
Patient initially has nonspecific viral symptoms, then develops a macular rash that is painful, pruritic, and morbilliform (macular/red/sometimes confluent like measles) on the face and trunk.
Lesions progress with sheets of epidermal detachment from dermis (Nikolsky's sign- separation of the skin with slight pressure- can be seen).
- Mucosal involvement is common
Rarely, internal organs, particularly in the respiratory/GI tracts can undergo necrosis, causing symptoms such as respiratory distress and diarrhea
DDx should include: Staphylococcal scalded skin syndrome (SSSS)/AKA Ritter diseases, Graft vs host disease (GVHD), bullous pemphigoid, pemphigus, acute generalized exanthematous pustulosis (also usually a febrile drug reaction occuring ~5 days after drug exposure, characterized by numerous small pustules but no mucosal involvement)

Withdraw causative drugs
Supportive care
- Wound care, infection control, fluid and electrolyte replacement
- Essentially waiting for the skin to heal on its own, similar to in burn patients
  - Re-epithelialization occurs within a few days to weeks
Some studies show improvement with IVIg but this is not standard of care
- Blocks TNF-alpha-induced apoptosis,
- Avoid this in renal failure
Steroids have been used in the past but there are no good trials that support their use and they have been demonstrated to be more harmful in advanced cases
Avoid silver-sulfadiazine in wound care since sulfas can induce SJS/TEN

Overall SJS has a 1-5% mortality; TEN has a 25-35% mortality, mostly due to infection of non-intact skin
The SCORTEN scale can be used in TEN, regular burns, or other cutaneous drug reactions to assess prognosis
- Risk factors include age, associated malignancy, heart rate, BUN, %tBSA involved, bicarbonate level, glucose level