What is the typical distribution of a Stevens-Johnson (Toxic Epidermal Necrolysis) rash?

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis Rash Distribution

Stevens-Johnson syndrome and toxic epidermal necrolysis rash typically begins on the upper torso, proximal limbs, and face, then spreads to involve the rest of the trunk and distal limbs, with prominent involvement of the palms and soles. 1

Initial Presentation and Distribution

• The earliest lesions appear as atypical targets and/or purpuric macules 1
• Initial sites of involvement are commonly the upper torso, proximal limbs, and face 1
• The rash then spreads to involve the rest of the trunk and distal limbs 1
• Involvement of the palms and soles is often prominent 1
• Mucosal involvement of the eyes, mouth, nose, and genitalia is usually an early feature 1

Rash Characteristics and Progression

• Lesions typically appear as numerous circular, dark red macules characterized by a dark red center surrounded by a pink ring 1
• Lesions expand and coalesce, reaching maximum extent 5-7 days after disease onset 1
• Large areas of confluent erythema develop in severe cases 1
• Lesional skin is tender to touch; minimal shearing forces cause the epidermis to peel back (positive Nikolsky sign) 1
• Blistering ensues with necrotic epidermis separating from underlying dermis, producing flaccid bullae 1
• Extensive necrolysis results in detachment of sheets of epidermis, leaving areas of exposed dermis 1

Classification Based on Extent of Involvement

The distribution pattern is similar across the spectrum of SJS/TEN, but classification depends on the extent of epidermal detachment:

• SJS: Epidermal detachment <10% body surface area (BSA) plus widespread purpuric macules or flat atypical targets 1, 2
• Overlap SJS-TEN: Detachment of 10-30% BSA plus widespread purpuric macules or flat atypical targets 1, 2
• TEN with spots: Detachment >30% BSA plus widespread purpuric macules or flat atypical targets 1
• TEN without spots: Detachment >30% BSA with loss of large epidermal sheets without purpuric macules or target lesions 1

Mucosal Involvement

• Involvement of the mucous membranes of the eyes, mouth, nose, and genitalia is usually an early feature 1, 3
• Mucosal involvement leads to an erosive and hemorrhagic mucositis 1
• In some cases, particularly those associated with Mycoplasma pneumoniae (especially in children), there may be predominantly mucous membrane involvement with little or no cutaneous lesions 1

Clinical Pitfalls and Important Considerations

• Cutaneous pain is a prominent early feature in SJS/TEN and should alert physicians to incipient epidermal necrolysis 1
• The Nikolsky sign (epidermal detachment with gentle lateral pressure) is helpful but not specific for SJS/TEN (also positive in pemphigus) 1
• Differentiation from erythema multiforme major (EMM) is important: EMM has typical targets or raised atypical targets predominantly on limbs and extremities, while SJS has atypical targets more widely distributed 1
• Documentation of both the extent of erythema AND epidermal detachment is crucial for prognosis assessment 2
• Denuded dermis exudes serum, becomes secondarily infected, and readily bleeds 1

Early recognition of the characteristic distribution pattern is critical for prompt diagnosis and management, as SJS/TEN is a medical emergency with mortality rates as high as 30% for TEN 4, 3.