Abstract

Lichen planus pemphigoides (LPP) is a rare autoimmune skin condition characterized clinically by lichenoid lesions accompanied by vesicle and/or bullae formation and is felt to be an overlap of lichen planus (LP) and bullous pemphigoid (BP). Confirming the diagnosis can be challenging given the variable clinical, histologic and direct immunofluorescence (DIF) findings that can be seen. We present 3 cases with unique clinical, histologic and DIF features and propose minimal diagnostic criteria for confirming the diagnosis of LPP. Histologically, lichenoid lesions demonstrate a variety of findings including focal hyperkeratosis, hypergranulosis, band-like lymphocytic infiltrate and/or vacuolar interface dermatitis with apoptotic keratinocytes (cytoid bodies), while bullae show subepidermal blister formation with eosinophilic infiltrate. DIF demonstrates shaggy, fibrillar fibrinogen deposition along the basement membrane zone (BMZ) with junctional cytoid bodies in lichenoid lesions and linear C3 and/or IgG deposition along the BMZ in perilesional tissue of bullae. Histologic and DIF findings are highly dependent on biopsy site selection in relation to the clinical features. Defining minimal diagnostic criteria for LPP is necessary to distinguish LPP from other diagnostic considerations and to minimize unnecessary multiple biopsies. Our proposed minimal diagnostic criteria for LPP are: 1) Clinical findings of lichenoid lesions with at least one tense bulla on affected or unaffected skin, 2) Histology of lichenoid lesions with features of a lichenoid interface process as described above, and 3) DIF demonstrating linear C3 and/or IgG along the BMZ. The proposed minimal diagnostic criteria simplify the clinical approach to patients with suspected LPP, allow for differentiation of LPP from alternative diagnoses including bullous LP and BP variants and minimize the need for additional biopsies that may be unnecessary to establish the diagnosis.

Financial Disclosure:
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