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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- SJS/TEN is a dermatologic emergency: skin pain, dusky macules, blistering, mucosal erosions, and epidermal detachment
- Classification by BSA detachment: SJS <10%, overlap 10-30%, TEN >30%
- Common culprit drugs: sulfonamides, allopurinol, lamotrigine, carbamazepine, phenytoin, phenobarbital, NSAIDs, nevirapine, antibiotics
- Immediate management: stop culprit drug, admit to ICU/burn unit, supportive wound/fluid/electrolyte care, ophthalmology, pain control, infection surveillance
- Do not confuse with staphylococcal scalded skin syndrome: SSSS spares mucosa; SJS/TEN involves mucosa
Overview
Stevens-Johnson syndrome and toxic epidermal necrolysis are a spectrum of severe immune-mediated keratinocyte apoptosis, most often triggered by medications. The key bedside clues are severe skin pain, systemic prodrome, dusky targetoid lesions, mucosal involvement, flaccid bullae, and epidermal sloughing. Mortality rises with age, comorbidity, renal dysfunction, tachycardia, malignancy, bicarbonate derangement, and extent of detachment. Because early withdrawal of the culprit drug improves outcomes, medication history over the preceding 1-8 weeks is critical.
Epidemiology
SJS/TEN is rare but high-mortality. HIV infection, malignancy, autoimmune disease, older age, and certain HLA alleles increase risk. HLA-B*1502 is associated with carbamazepine SJS/TEN in many Asian ancestry populations; HLA-B*5801 is associated with allopurinol severe cutaneous adverse reactions. Mycoplasma pneumoniae can trigger SJS-like mucositis, particularly in children and adolescents.
Clinical Features
Symptoms
Prodrome of fever, malaise, sore throat, cough, burning eyes 1-3 days before rash
Severe skin pain out of proportion to early visible rash
Painful oral, ocular, genital, or anal mucosal erosions
Photophobia, red eyes, decreased vision
Recent high-risk drug started days to weeks earlier
Signs
Dusky red or purpuric macules with atypical target lesions that coalesce
Flaccid bullae, epidermal detachment, positive Nikolsky sign
Mucosal involvement at two or more sites is common
Tender erythematous skin with sheet-like sloughing
Hemodynamic instability, dehydration, hypothermia, or sepsis physiology
Investigations
First-line
Immediate medication timelineIdentify all new drugs in previous 1-8 weeks, including antibiotics, anticonvulsants, allopurinol, NSAIDs, antiretrovirals, OTC/herbals
Clinical BSA assessmentEstimate detached/detachable epidermis: SJS <10%, overlap 10-30%, TEN >30%
Baseline labsCBC, CMP, bicarbonate, glucose, BUN/Cr, LFTs, lactate if ill, cultures only if infection suspected
Second-line
Skin biopsy with frozen/permanent sectionsFull-thickness epidermal necrosis with sparse inflammation confirms diagnosis and helps exclude mimics
SCORTENMortality score using age >40, malignancy, HR >120, BSA detachment >10%, BUN >28, glucose >252, bicarbonate <20
Specialist
Ophthalmology examinationUrgent early assessment even if eye symptoms are mild to prevent symblepharon, scarring, and vision loss
Infectious evaluationMycoplasma testing in children/young adults with prominent mucositis; cultures if sepsis or wound infection suspected
1
Immediate actions
- Stop suspected culprit medication(s) immediately
- Admit to burn unit or ICU with dermatology consultation; early transfer improves outcomes
- Airway, breathing, circulation assessment; aggressive pain control; temperature control
- Document culprit drug as severe allergy and avoid rechallenge
2
Supportive care
- Fluid and electrolyte management similar to burns but often lower requirements than thermal burns
- Non-adherent wound dressings, gentle handling, avoid debridement of intact detached epidermis unless specialist-directed
- Nutritional support, VTE prophylaxis, stress-ulcer prophylaxis as appropriate
- Infection surveillance; do not give prophylactic systemic antibiotics without evidence of infection
3
Mucosal and organ protection
- Ophthalmology: lubrication, topical antibiotics/steroids or amniotic membrane when indicated
- Oral/genital wound care, urinary catheter only when necessary, gynecology/urology if severe genital involvement
- Monitor renal, hepatic, pulmonary, and GI complications
4
Disease-modifying therapy
- Evidence varies; specialist-directed options may include cyclosporine, etanercept, IVIG, or systemic corticosteroids depending on center protocol and timing
- The universally correct first Step 2 CK action is stopping the drug and supportive burn-unit/ICU care
Complications
- Sepsis and multiorgan failure: Leading causes of death
- Ocular scarring: Symblepharon, dry eye, corneal ulceration, blindness
- Fluid/electrolyte loss: Dehydration, AKI, hypothermia
- Respiratory involvement: Bronchiolitis, pneumonitis, airway sloughing
- Long-term mucosal sequelae: Oral, genital, urinary, and GI strictures/scarring
- Medication recurrence: Rechallenge can be fatal
USMLE Step 2 CK Exam Tips
- 1Skin pain + mucosal erosions + targetoid/dusky rash after new drug = SJS/TEN
- 2SJS <10% BSA; TEN >30%; overlap 10-30%
- 3Stop the culprit drug immediately and admit to burn unit/ICU
- 4SSSS spares mucosa; SJS/TEN involves mucosa
- 5High-yield culprit drugs: sulfonamides, allopurinol, lamotrigine, carbamazepine, phenytoin, NSAIDs
- 6Do not choose prophylactic antibiotics; treat infection only if suspected/confirmed
- 7Ophthalmology early even when eye symptoms seem mild
- 8HLA-B*1502 before carbamazepine in at-risk Asian ancestry patients; HLA-B*5801 for allopurinol risk in selected populations
practicetest your knowledge on stevens-johnson syndrome / toxic epidermal necrolysisApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — dermatology and beyond.
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