Version July 2025
| Disorder | Associated conditions | Clinical features | Pathology | Laboratory findings |
| Herpes simplex virus (HSV) | None | Recurrent, grouped vesicles; most commonly found on lips or genitalia | H&E: intraepidermal blister; ballooning of keratinocyte cytoplasm and margination of chromatin to form intranuclear inclusion bodies; mixed inflammatory infiltrate | Viral culture, Tzanck smear, HSV DFA, PCR |
| Erythema multiforme | HSV or Mycoplasma pneumoniae infection, occasionally drug exposure | Mucosal erythema and erosions, most frequently involving oral cavity; target lesions on skin | H&E: vacuolar interface dermatitis, necrotic keratinocytes, subepidermal clefts and vesiculation | HSV testing on active lesions, serology, or biopsy specimen; testing for M. pneumoniae infection |
| Pemphigus vulgaris | None | Vesicles, erosions and desquamative gingivitis | H&E: intraepidermal vesicle, acantholysis DIF: intercellular epidermal IgG deposition | IIF: intercellular IgG staining of skin substrate, IgG antidesmoglein 3 |
| Mucous membrane pemphigoid* | Reflects a diverse group of subepidermal blistering disorders with mucous membranes as the primary site of involvement | Vesicles and erosions, desquamative gingivitis; can have ocular involvement and symblepharon | H&E: subepidermal blisters; inflammatory infiltrate and DIF findings vary with subtype | IIF: varies with subtype |
| Stevens-Johnson syndrome and toxic epidermal necrolysis | Medication, Mycoplasma infection | Exudative erosions of lips, oral mucosa, eyes, genital mucosa; targetoid papulovesicles of skin, skin sloughing, skin pain | H&E: vacuolar interface dermatitis or epidermal necrosis | None |
| Paraneoplastic pemphigus | Underlying malignancy | Targetoid papulovesicles; erythema multiforme-like cutaneous lesions; exudative erosions of lips, oral mucosal, eyes, genital mucosa | H&E: mixed histology; overlapping features of pemphigus vulgaris, erythema multiforme, and lichen planus DIF: intercellular IgG deposition; basement membrane zone IgG deposition also may be present | IIF: intercellular IgG deposition on transitional epithelium (rodent bladder) |
