What are the clinical features of Stevens-Johnson syndrome and how can it be distinguished from other rashes?

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Last updated: October 1, 2026 • View editorial policy

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Stevens-Johnson Syndrome: Clinical Appearance and Differentiation

Stevens-Johnson syndrome presents with painful, dusky red or purpuric flat macules and atypical targets that start on the face and upper torso, accompanied by severe erosive mucositis affecting at least two mucosal sites (eyes, mouth, nose, genitalia), with less than 10% body surface area epidermal detachment. 1

Key Clinical Features

Prodromal Phase

  • Fever, malaise, and upper respiratory symptoms precede skin eruption by several days 1, 2
  • Cutaneous pain is a prominent early warning sign that should immediately alert you to incipient epidermal necrolysis 2
  • Ocular inflammation may develop before skin signs appear 2

Skin Manifestations

The earliest cutaneous lesions are:

  • Flat atypical targets (not the raised, well-defined targets of erythema multiforme)
  • Purpuric macules (dark red, flat lesions) 1
  • Initial distribution: upper torso, proximal limbs, and face, then spreading to trunk and distal limbs 1
  • Prominent involvement of palms and soles 1

As disease progresses:

  • Lesions coalesce into large areas of confluent dusky erythema 1
  • Positive Nikolsky sign: gentle lateral pressure causes epidermis to slide over dermis 1
  • Flaccid bullae develop as necrotic epidermis separates from dermis 1
  • Sheets of epidermis detach, leaving exposed, weeping dermis that bleeds easily 1, 2
  • Maximum extent reached 5-7 days after onset 1

Mucosal Involvement

  • Usually an early feature affecting eyes, mouth, nose, and genitalia 1
  • Erosive and hemorrhagic mucositis 1
  • Purulent keratoconjunctivitis with eyelid edema 1

Critical Differentiating Features from Other Rashes

Erythema Multiforme Major (EMM)

The most important distinction:

  • EMM: Typical targets or raised atypical targets, predominantly on extremities (acral distribution) 1
  • SJS: Flat atypical targets or purpuric macules, widespread or on trunk 1, 3
  • EMM: Usually herpes simplex virus-related; patients constitutionally well 2, 3
  • SJS: Usually drug-induced; patients systemically ill 1, 3
  • EMM: Mucosal involvement typically confined to mouth 2
  • SJS: Multi-site mucosal involvement (≥2 sites) 1

A landmark study demonstrated 87% correlation between clinical pattern and cause: EMM was herpes-related in 17/28 cases and never drug-induced, while SJS was drug-related in 28/33 cases and never herpes-related 3.

Staphylococcal Scalded Skin Syndrome (SSSS)

Key differentiator in children:

  • SSSS: No mucosal involvement - this is the clinical hallmark 2
  • SSSS: Intraepidermal cleavage (more superficial) 2
  • SJS: Subepidermal cleavage 2
  • When uncertain, skin biopsy or frozen section of blister roof definitively distinguishes them 2

Drug Hypersensitivity Syndrome/DRESS

  • More gradual onset (weeks vs. days)
  • Morbilliform eruption rather than purpuric macules
  • Eosinophilia and organ involvement (hepatitis, nephritis)
  • Less prominent mucosal involvement 4

Morbilliform Drug Eruption

  • Blanching erythematous papules and macules
  • No epidermal detachment or blistering
  • Minimal or no mucosal involvement 4

Acute Generalized Exanthematous Pustulosis (AGEP)

  • Numerous sterile pustules on erythematous base
  • Rapid onset (typically <48 hours after drug exposure)
  • Minimal mucosal involvement
  • Neutrophilia rather than lymphopenia 4

Immunobullous Disorders (Pemphigus, Pemphigoid)

  • Different histopathology: acantholysis in pemphigus, subepidermal split with eosinophils in pemphigoid 1
  • Chronic course rather than acute
  • Positive direct immunofluorescence
  • Less systemic toxicity 2

Predictive Clinical Model

A 2019 study identified four key features that predict SJS/TEN 4:

  1. Nikolsky sign (positive)
  2. Atypical targets (flat, not raised)
  3. Fever (present)
  4. Lymphopenia (present)

The presence of these features significantly increases probability of SJS/TEN over mimickers.

Diagnostic Confirmation

Histopathology

  • Variable epidermal damage from individual cell apoptosis to confluent epidermal necrosis 1, 2
  • Basal cell vacuolar degeneration 1
  • Subepidermal vesicle or bulla formation 1, 2
  • Mild perivascular lymphocytic infiltrate in dermis 1
  • Occasional eosinophils 1

Common Pitfall: Do not delay treatment waiting for biopsy results. Clinical diagnosis should prompt immediate action, with biopsy serving to confirm and exclude other blistering disorders 1, 2.

Clinical Phenotype Classification

Based on extent of epidermal detachment 1, 2:

  • SJS: <10% BSA detachment plus widespread purpuric macules/flat atypical targets
  • SJS-TEN overlap: 10-30% BSA detachment
  • TEN: >30% BSA detachment

Mycoplasma-Associated Variant

In children, Mycoplasma pneumoniae can cause a phenotype with predominantly mucous membrane involvement with minimal cutaneous lesions, termed "Mycoplasma pneumoniae-associated mucositis" 1, 5. This variant may present with severe odynophagia and mucosal ulceration without the typical widespread rash, making early recognition challenging 5.

References

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