Erythema multiforme vs SJS/TEN
How to tell Erythema multiforme and SJS/TEN apart when a board question makes them look alike.
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Mucosal erosions with epidermal detachment after a high-risk drug indicate SJS/TEN rather than erythema multiforme.
Side by side
Target lesions on extremities with minimal mucosal involvement and stable hemodynamics suggest erythema multiforme.
Widespread painful dusky lesions with mucosal erosions and epidermal detachment suggest Stevens-Johnson syndrome or toxic epidermal necrolysis.
Erythema multiforme is a cell-mediated reaction often triggered by herpes simplex infection.
SJS and TEN are severe drug-triggered keratinocyte apoptosis syndromes causing epidermal necrosis and sloughing.
Diagnosis is clinical; lesions are typical targetoid papules with central dusky zone and usually involve less than 10% body surface without extensive epidermal detachment.
SJS involves less than 10% body surface detachment, TEN above 30%, and overlap 10 to 30%; biopsy shows full-thickness epidermal necrosis and supportive severity markers include rising BUN, bicarbonate drop, and tachycardia.
The trap
Target-like lesions can falsely reassure clinicians into diagnosing benign erythema multiforme. Painful skin, oral or ocular mucosal injury, and positive Nikolsky sign should trigger immediate burn-unit style care and culprit drug withdrawal.
The repair move
Next best step: stop the culprit medication immediately, admit for intensive supportive care with fluid and electrolyte management, wound care, pain control, and ophthalmology evaluation. Manage as SJS/TEN severity syndrome with early multidisciplinary care similar to burn management; avoid unnecessary antibiotic prophylaxis unless infection is documented.
Try a free question
CoreA 22-year-old man develops target lesions on hands and forearms after recurrent herpes labialis. BP 118/72 mm Hg, HR 78/min, temp 37.0 C. He has no oral erosions and no epidermal sloughing. What is the most likely diagnosis?
Show answer and explanation
Answer: B. Erythema multiforme. Classic target lesions with minimal mucosal involvement after HSV trigger are consistent with erythema multiforme.
Why the other choices are tempting
- A. SJS usually includes painful mucosal erosions and epidermal detachment often linked to drug exposure.
- C. Pemphigus vulgaris presents with flaccid bullae and mucosal erosions, not classic acral targets.
- D. Bullous pemphigoid typically affects older adults with tense bullae and less target morphology.
- E. Staphylococcal scalded skin syndrome is usually pediatric and toxin-mediated with superficial desquamation.
Flashcards
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What lesion pattern is classic for erythema multiforme minor?
Symmetric target lesions on extremities with little or no mucosal involvement are classic for erythema multiforme minor.
What bedside feature strongly indicates SJS/TEN?
Painful mucosal erosions with epidermal detachment strongly indicates SJS/TEN.
Quick answers
What is the fastest way to tell Erythema multiforme from SJS/TEN?
Mucosal erosions with epidermal detachment after a high-risk drug indicate SJS/TEN rather than erythema multiforme.
What is the key clue for Erythema multiforme?
Target lesions on extremities with minimal mucosal involvement and stable hemodynamics suggest erythema multiforme.
What is the key clue for SJS/TEN?
Widespread painful dusky lesions with mucosal erosions and epidermal detachment suggest Stevens-Johnson syndrome or toxic epidermal necrolysis.
What is the common trap with Erythema multiforme vs SJS/TEN?
Target-like lesions can falsely reassure clinicians into diagnosing benign erythema multiforme. Painful skin, oral or ocular mucosal injury, and positive Nikolsky sign should trigger immediate burn-unit style care and culprit drug withdrawal.