Stevens-Johnson syndrome and toxic epidermal necrolysis

Overview

SJS and TEN are a spectrum of severe, life-threatening drug-induced mucocutaneous reactions characterised by widespread epidermal detachment and mucosal erosions. Distinction is by percentage BSA affected.

Classification

SJS vs overlap vs TEN by BSA detachment
FeatureSJSSJS-TEN overlapTEN
BSA detachment<10%10-30%>30%
Mortality~5-10%Intermediate25-40%

Feature	SJS	SJS-TEN overlap	TEN
BSA detachment	<10%	10-30%	>30%
Mortality	~5-10%	Intermediate	25-40%

Presentation

•Prodrome (1-3 days before skin eruption): fever, malaise, sore throat, burning eyes, dysphagia - onset 1-3 weeks after starting causative drug

•Skin lesions: dusky-red erythematous macules or atypical (flat) target lesions - trunk, face, proximal limbs, palms and soles

•Epidermal detachment: blisters coalesce, epidermis peels in sheets

•Nikolsky sign positive: lateral shear on intact erythematous skin causes epidermis to slide off

•Mucosal involvement (>90%): oral erosions/haemorrhagic crusting, conjunctivitis, genital/urethral erosions

•Systemic: fever, tachycardia, hypotension, confusion in severe cases

🚨
Prodromal fever, sore throat, and burning eyes in a patient recently started on carbamazepine, lamotrigine, or allopurinol = SJS/TEN until proven otherwise. Stop the drug immediately - do not wait for blistering.

Investigations

•Clinical diagnosis - history, morphology, BSA assessment; investigations support management

•Skin biopsy: full-thickness epidermal necrosis - distinguishes from SSSS (superficial/subcorneal cleavage)

•FBC, U&E, LFTs, CRP: electrolyte derangement, organ involvement; lymphopenia = severity marker

•Cultures (blood, skin, sputum): infection is leading cause of death

•Ophthalmology review: slit-lamp for conjunctival/corneal involvement - essential in all confirmed cases

•SCORTEN score: calculate on admission and day 3 to stratify mortality

Differential diagnosis

Key differentials
FeatureSJS/TENErythema multiformeSSSS
Lesion morphologyFlat dusky macules, blistersRaised 3-zone target lesionsSuperficial blistering/peeling
TriggerDrugs (>85%)HSV/MycoplasmaStaphylococcal exotoxin
Mucosal involvement>90%Less severeAbsent
Biopsy cleavageFull-thickness epidermalMinimal detachmentSuperficial (subcorneal)
Relation to SJS spectrum-Distinct - NOT on same spectrumDistinct

Feature	SJS/TEN	Erythema multiforme	SSSS
Lesion morphology	Flat dusky macules, blisters	Raised 3-zone target lesions	Superficial blistering/peeling
Trigger	Drugs (>85%)	HSV/Mycoplasma	Staphylococcal exotoxin
Mucosal involvement	>90%	Less severe	Absent
Biopsy cleavage	Full-thickness epidermal	Minimal detachment	Superficial (subcorneal)
Relation to SJS spectrum	-	Distinct - NOT on same spectrum	Distinct

Management

•Immediate: stop causative drug - single most important intervention

•Specialist setting: dermatology ward; extensive BSA involvement warrants burns unit transfer

•Supportive care: IV fluid resuscitation, electrolyte replacement, non-adherent wound dressings, nutritional support

•Ophthalmology: urgent review for all confirmed cases

•Immunomodulation (specialist decision): ciclosporin is considered

⚠️
Prophylactic antibiotics are NOT recommended - empirical use selects for resistant organisms and increases mortality. Use antibiotics only for confirmed infection guided by cultures.

Complications

•Sepsis - leading cause of death; Staphylococcus aureus and Pseudomonas aeruginosa common

•Ocular: symblepharon, corneal scarring, dry eye, permanent visual impairment

•Respiratory failure: tracheobronchial mucosal sloughing, ARDS

•Genitourinary: urethral strictures, vaginal adhesions

•Long-term: post-inflammatory hyperpigmentation, PTSD

📌
Survivors must never re-take the causative drug or structurally related compounds. Document allergy in all medical records, issue allergy alert card, and inform GP and all future prescribers.

Causative drugs

•High-risk drugs (must know): carbamazepine, lamotrigine, allopurinol, sulfonamides, phenobarbital, phenytoin

•Other implicated drugs: salicylates, sertraline, imidazole antifungals, nevirapine

•Non-drug triggers (especially in children): Mycoplasma pneumoniae, HSV

💡
HLA-B*15:02 strongly associated with carbamazepine-induced SJS/TEN in Han Chinese, Thai, and South-East Asian populations - MHRA recommends HLA screening before prescribing carbamazepine in these groups.

SCORTEN score

Each criterion scores 1 point. Calculate on day 1 and day 3.

SCORTEN criteria (1 point each)
Age >40 years
Malignancy present
BSA detachment >10% at presentation
Heart rate >120 bpm
Serum urea >10 mmol/L
Serum bicarbonate <20 mmol/L
Serum glucose >14 mmol/L

•Score 0-1 = ~3% mortality; score ≥5 = >90% mortality