Table 2.

Summary of characteristics of BSLE, SJS, and TEN-like lupus, FDE, EM, and SJS/TEN

	BSLE	SJS AND TEN-LIKE LUPUS	FDE	EM	SJS/TEN
Cause	Antibodies to collagen VII	No clear drug association, may have history of recent LE exacerbation	Drug-induced	>90% caused by infections, most commonly HSV	Drugs cause in 80%, infections are rare
Distribution	Any cutaneous site with predilection for the face, upper trunk, and proximal extremities, can have mucosal involvement	Photodistribution, No or limited mucosal involvement	May occur on any site on skin/mucosa, most commonly palms, soles, lips, and glans penis16	Typically lesions on extremities and face	Typically start on the trunk and can spread to the neck/face and proximal upper extremities, generally spare distal extremities
Lesion morphology	Tense bullae on an erythematous or urticated base	Preceded by characteristic cutaneous LE lesions. Develop over weeks to months	Sharply marginated round- or oval-shaped lesions that can have bullae. Usually few and localized, but can be multiple and disseminated	Typical target (well-defined border and three distinct zones). Atypical target lesions are palpable and have only two zones and/or a poorly defined border	Atypical target lesions if present have only two zones or a poorly defined border, but are macular. Develop over hours to days
Recurrent cases			Minutes-hours after re-exposure to medication. Occur in the same location as previous episodes	More frequently recurrent compared to SJS/TEN, recurrences due to HSV common	As early as 2 days. No predilection for previously affected sites
H&E	Subepidermal blister with neutrophilic infiltrate in upper dermis (papillary microabscesses or band-like infiltrate)	Junctional vacuolar alteration, presence of solitary necrotic keratinocytes at lower epidermal levels, moderate-to-dense periadnexal and perivascular lymphocytic infiltrate, thickened BMZ, presence of plasma cells, melanophages, mucin	Superficial and deep perivascular mixed infiltrate with lymphocytes, histiocytes, neutrophils, and eosinophils (eosinophils may predominate)	Superficial perivascular infiltrate with lymphocytes and histiocytes	Superficial perivascular infiltrate with lymphocytes and histiocytes. Typically characterized by little or no inflammation, but drug-related cases may have a substantial number of eosinophils
DIF	IgG, IgM, IgA, and C3 at the BMZ	Most characteristic— IgG and/or IgM (IgA less commonly) granular deposits at dermal-epidermal junction and around hair follicles, (neg DIF does not rule out LE)	Not well described (reports of linear IgG and C3 deposition along the BMZ, perivascular and stippled band of C3 at the BMZ, intercellular IgG and C3 reported.)25	Not specific (C3 and IgM in blood vessels in the upper dermis, C3 may be found along BMZ and focally in Civatte bodies)26	Not specific (C3 around blood vessels, IgM, and C3 at the dermoepidermal junction)26