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Clinical features
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• Mostly drug-related
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• May be idiopathic or drug-induced
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Although the rapidity and severity of symptom progression favored a working diagnosis of SJS, on clinical grounds it was not possible to distinguish between SJS and SCLE in the case presented
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• Characterized as dusky erythematous lesions; lesions tend to be isolated but can have confluence on the face and trunk
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• Characterized as erythematous, papulosquamous or polycyclic annular plaques, typically non-scarring
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• Typically involves the trunk, back, and extremities including palms and soles, neck, and face; often associated with painful mucosal surfaces
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• Typically consists of photosensitive regions with lesions confined to sun-exposed skin (upper trunk/back, shoulders, extensor arms, neck, lateral aspects of face) with mid-facial sparing
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• Usually occurs within 7 to 21 days after initiation of the causative drug
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• Latent period between drug administration and the appearance of symptoms can range from several weeks to several years (in drug-induced SCLE)
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Histological features
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• In early lesions, apoptotic keratinocytes are observed scattered in the supra-basal layers of the epidermis
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• Epidermal changes and a superficial lymphocytic infiltrate in the upper dermis with apoptotic keratinocytes
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Histological findings of an interface dermatitis with dermal mucin deposition is most consistent with a diagnosis of SCLE
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• In late stages, a sub-epidermal blister with overlying confluent necrosis of the entire epidermis and spare peri-vascular infiltrate composed primarily of lymphocytes is seen
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• Dermal mucin deposits are commonly identified
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