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ukmla 2026

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Severe life-threatening mucocutaneous reactions with epidermal necrosis — SJS (<10% BSA), overlap (10-30%), TEN (>30%). Usually drug-induced

Review date
reviewed 2026-04-05
Reading time
5 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Dermatologyrareacute
On this page
Condition details
Dermatology
rare
5 min read
reviewed 2026-04-05
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About This Page

This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.

Key points

  • SJS <10% BSA, overlap 10-30%, TEN >30%. Mortality: SJS ~5%, TEN ~30%
  • Usually drug-induced (>80%): allopurinol, carbamazepine, lamotrigine, phenytoin, sulfonamides, NSAIDs
  • Prodrome then dusky macules, sheet-like epidermal detachment, mucosal erosions (>90%)
  • Nikolsky sign POSITIVE: skin shears off with lateral pressure
  • EMERGENCY: STOP causative drug immediately. Burns unit/ICU. Supportive care

Overview

SJS and TEN are a spectrum of severe mucocutaneous reactions with widespread keratinocyte apoptosis and epidermal detachment. >80% drug-induced (1-3 weeks after initiation). Pathogenesis involves cytotoxic T cells and NK cells causing apoptosis via Fas-FasL and granulysin. Mucous membrane involvement in >90%. A dermatological emergency with significant mortality.

Epidemiology

SJS ~1-6 per million/year; TEN ~0.4-1.2 per million/year. 100x higher in HIV-positive. Common causative drugs: allopurinol, aromatic anticonvulsants, sulfonamides, NSAIDs, nevirapine. Pharmacogenomic risk: HLA-B*5801 (allopurinol), HLA-B*1502 (carbamazepine in SE Asian populations).

Clinical Features

Symptoms
Prodrome: fever, malaise, sore throat 1-3 days before rash
Painful burning skin — widespread
Oral erosions, ocular pain, genital ulceration (mucosal involvement >90%)
Recent new medication 1-3 weeks prior
Signs
Widespread dusky macules and atypical targets with necrotic centres
Sheet-like epidermal detachment — skin peels leaving raw dermis
Nikolsky sign POSITIVE
Haemorrhagic lip crusting, bilateral purulent conjunctivitis

Investigations

First-line
Drug historyIdentify causative agent (started 1-3 weeks prior)
Skin biopsyFull-thickness epidermal necrosis with subepidermal split
Second-line
SCORTEN scorePrognostic: age >40, malignancy, HR >120, BSA >10%, urea >10, glucose >14, bicarb <20
BloodsFBC, U&E, LFT, glucose, bicarb, cultures
Specialist
OphthalmologyUrgent — ocular involvement common, risk of permanent scarring

Management

BAD Guidelines on SJS/TEN
1
STOP the drug
  • IMMEDIATELY discontinue suspected drug — most important intervention
  • Early withdrawal reduces mortality
2
Supportive care — burns unit/ICU
  • Manage as burns: fluids, temperature, nutrition
  • Non-adherent dressings, avoid debridement of attached epidermis
  • Pain: often requires opioids
  • Infection monitoring — sepsis is leading cause of death
3
Mucosal care
  • Oral: mouthwashes, lip care, NG feeding if needed
  • Ocular: URGENT ophthalmology — lubricants, daily slit lamp
  • Genital: catheterisation if urethral involvement
4
Drug NEVER to be used again
  • Absolute contraindication for life to causative drug class

Complications

  • Mortality: SJS ~5%, TEN ~25-35%. Sepsis and MOF leading causes
  • Ocular: Scarring, symblepharon, dry eyes, blindness — commonest long-term complication
  • Mucosal strictures: Oesophageal, urethral
  • PTSD/depression
UKMLA Exam Tips
  • 1SJS <10%, overlap 10-30%, TEN >30% BSA
  • 2Common drugs: Allopurinol, Carbamazepine, Lamotrigine, Sulfonamides (ACLS)
  • 3Nikolsky positive = epidermis shears off — also seen in pemphigus vulgaris
  • 4STOP the drug IMMEDIATELY — delay increases mortality
  • 5SJS/TEN: full-thickness necrosis at dermo-epidermal junction. SSSS: superficial intra-epidermal
  • 6Atypical targets (flat, 2-zone) in SJS/TEN. TRUE targets (3-zone) in erythema multiforme
  • 7Urgent ophthalmology — ocular complications are most common long-term morbidity

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Verified Sources & References

BAD — Management of SJS/TEN
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