Erythema and epidermal/mucosal detachment (erosions, blisters), typically spreading from the trunk towards the face and upper proximal extremities, are the main symptoms of SJS/TEN. Cutaneous lesions first present as erythematous, dusky red or purpuric macules, that progressively (within hours-days) take on a characteristic gray hue as a result from epidermal necrosis progression. The necrotic epidermis then detaches from the underlying dermis and fluid accumulation in the dermo-epidermal cleft gives rise to blisters.
Quantification of detached and detachable epidermis (positive Nikolsky sign) allows to classify patients into three groups that are variants of the same disease which differ in the extent of skin detachment (figure to be inserted):
- SJS: <10% of body surface area (BSA)
- SJS–TEN overlap (an intermediate category): 10–30% of BSA
- TEN: >30% of BSA.
Buccal, ocular and genital mucosae are affected in more than 90% of patients, respiratory and gastrointestinal tract involvement and systemic symptoms (e.g. fever, severe anxiety, lymphadenopathy, and hepatitis) can also occur.
Prodromal systemic symptoms such as fever, dysphagia or stinging eyes can precede the onset of cutaneous manifestations in SJS/TEN by up to three days.