Challenges and pitfalls between lichen planus pemphigoides and bullous lichen planus.

Lichen planus pemphigoides (LPP) and bullous lichen planus (BLP) are rare dermatoses, which are characterised by blisters and lichenoid lesions. Their clinical presentation is heterogenous, displaying overlapping features or mimicking other dermatological diseases. Therefore, diagnosis can often be challenging, requiring a thorough dermatological examination along with distinctive histological and immunopathological characteristics. Lichenoid degeneration of the basal epidermis exposes various antigens of the dermal-epidermal junction in LPP, resulting in the breakdown of immune tolerance, hence, the production of autoantibodies against type XVII collagen. Conversely, no pathogenic autoantibodies are detected in BLP. However, some cases of mucosal lichen planus might display immunopathological features suggestive of autoimmune blistering diseases. Therefore, a better understanding of the pathophysiology of these two distinct dermatoses is imperative. The aim of this review was to provide a summary of the current knowledge on the clinical hallmarks, diagnosis and available therapeutic options in LPP and BLP.