Stevens-Johnson Syndrome
Dermatology
Illness script · Dermatology
Stevens-Johnson Syndrome
Severe mucocutaneous hypersensitivity reaction with epidermal detachment involving <10% BSA, caused by drugs or infections.
This illness script for Stevens-Johnson Syndrome covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Most common triggers: sulfonamides, allopurinol, anticonvulsants (carbamazepine, phenytoin, lamotrigine), NSAIDs
- HIV infection markedly increases risk (1000×)
- HLA-B*15:02 (carbamazepine) and HLA-B*58:01 (allopurinol) are genetic risk alleles
- Mycoplasma pneumoniae is the leading infectious trigger, especially in children
- Peak onset 4–28 days after starting culprit drug
02
Presentation
- Prodrome: fever, malaise, URI symptoms 1–3 days before rash
- Painful erythematous/dusky macules → blisters → epidermal sloughing <10% BSA
- Positive Nikolsky sign: lateral pressure causes skin to shear off
- ≥2 mucosal surfaces involved (oral, ocular, genital) — hallmark feature
- Target lesions are atypical (flat, two-zone) vs. classic EM targets
- Ocular involvement (pseudomembrane, symblepharon) can cause permanent blindness
03
Pathophysiology
- Drug or metabolite acts as hapten → cytotoxic T-cell (CD8+) attack on keratinocytes
- Fas-FasL and granulysin-mediated keratinocyte apoptosis → full-thickness epidermal necrosis
- Mucosal surfaces (oral, ocular, genital) heavily involved due to shared immune mechanism
- Loss of skin barrier → fluid loss, sepsis, multiorgan failure
04
Diagnostics
- Clinical diagnosis based on morphology, BSA involved, and mucosal involvement
- Skin biopsy: full-thickness epidermal necrosis with sparse dermal inflammation — confirms diagnosis
- SCORTEN score calculated at admission to predict mortality
- Discontinue all non-essential drugs immediately upon suspicion
- Rule out infection (CBC, blood cultures, CXR) — sepsis is leading cause of death
05
Management
- IMMEDIATE drug withdrawal — most critical intervention; delays worsen mortality
- Admit to burn unit or ICU; treat like a burn patient (fluids, wound care)
- Ophthalmology consult urgently — eye care is time-sensitive
- IVIG or cyclosporine used in some centers; systemic steroids are controversial/generally avoided
- Supportive care: nutritional support, pain control, infection surveillance; mortality ~5–10% for SJS
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Toxic Epidermal Necrolysis (TEN)
Epidermal detachment >30% BSA (SJS <10%, SJS-TEN overlap 10–30%); same pathomechanism, worse prognosis
Erythema Multiforme Major
Classic 3-zone target lesions, <10% BSA, mucosa often involved but usually 1 site; typically post-HSV, NOT drug-induced
Staphylococcal Scalded Skin Syndrome
SSSS occurs in children/immunocompromised; biopsy shows subcorneal split (not full-thickness); no mucosal involvement
Drug Hypersensitivity Syndrome (DRESS)
DRESS has extensive morbilliform rash + internal organ involvement (hepatitis, eosinophilia) but NO epidermal detachment
Keep reading
Full library- Status EpilepticusSeizure lasting ≥5 minutes OR ≥2 seizures without return to baseline consciousness between them.
- Subarachnoid HemorrhageBleeding into the subarachnoid space, most often from a ruptured intracranial aneurysm, causing sudden severe headache.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.