What are the key differences between Erythema Multiforme (EM) minor and major, Toxic Epidermal Necrolysis (TEN), Stevens-Johnson Syndrome (SJS), and Staphylococcal Scalded Skin Syndrome (SSSS)?

From the Guidelines

For USMLE preparation, it is crucial to distinguish between erythema multiforme (EM), toxic epidermal necrolysis (TEN), Stevens-Johnson syndrome (SJS), and staphylococcal scalded skin syndrome (SSSS) based on their clinical presentations, triggers, and management approaches, as outlined in the British Association of Dermatologists' guidelines 1.

Key Differences

• Erythema multiforme minor presents with target lesions on extremities, often triggered by HSV infection, with minimal mucosal involvement and good prognosis.
• Erythema multiforme major shows more extensive target lesions with significant mucosal involvement.
• Stevens-Johnson syndrome involves <10% body surface area detachment, presents with atypical target lesions, painful mucosal erosions, and is commonly triggered by medications like sulfonamides, anticonvulsants, and allopurinol.
• TEN represents the severe end of the SJS spectrum with >30% body surface area detachment, widespread epidermal necrosis, and high mortality (30-40%).
• SJS-TEN overlap involves 10-30% body surface area detachment.
• SSSS, caused by Staphylococcus aureus exfoliative toxins, primarily affects children, presents with diffuse erythema followed by large flaccid bullae and desquamation, but importantly spares mucous membranes and shows cleavage at the granular layer.

Management Approaches

• EM minor is self-limited.
• SJS/TEN requires immediate drug discontinuation and supportive care (possibly IVIG or cyclosporine) 1.
• SSSS requires antibiotics targeting S. aureus.

Supportive Care

• Supportive care is the most important aspect in the treatment of patients of all ages with SJS/TEN, including care of skin, mucous membranes, resuscitation, fluid balance, nutritional support, analgesia, and preventing life-threatening complications and long-term morbidity 1.
• Age-appropriate strategies, including play specialists, distraction, and involvement of parents, should be utilized.
• A recent systematic review highlighted the need for more standardized treatment and reporting to compare morbidity and mortality outcomes between different approaches 1.

From the Research

Erythema Multiforme Minor and Major

• Erythema multiforme (EM) is an immune-mediated epidermal condition with variable clinical presentations 2
• EM is caused by infections in more than 90% of cases, especially Herpes virus infection 3
• The majority of EM cases are caused by infections, primarily herpes simplex virus and Mycoplasma pneumoniae 4

Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)

• SJS and TEN are acute bullous disorders associated with different prognoses, mainly due to infections and drugs 3
• SJS and TEN are referable to drugs in more than 95% of cases 3
• The SCORTEN (score of toxic epidermal necrolysis) can be used to assess disease prognosis in patients with SJS/TEN 4

Key Points for USMLE

• EM, SJS, and TEN are distinct conditions with different etiologies and potential outcomes 5
• The clinical distinction between EM, SJS, and TEN can be uncertain and controversial, but diagnosis and management can be guided by the morphology of individual lesions, pattern of distribution, and etiopathogenesis 4
• Frozen-section diagnosis can be useful in diagnosing and predicting disease activity in patients with EM-like lesions 6
• Cyclosporine may be able to halt disease progression and lower mortality rates in SJS/TEN, but there is still uncertainty as to the type of systemic therapy required 4

Staphylococcal Scalded Skin Syndrome (SSSS)

• No specific information is available in the provided studies to distinguish SSSS from EM, SJS, and TEN, but it is a separate condition that can be considered in the differential diagnosis 4, 3, 2, 5, 6