Pseudoepitheliomatous changes in a case of vegetating Darier–White disease: a unique histopathological finding.

Darier–White disease (DWD) is a rare autosomal dominant genodermatosis, characterized by constant and typical histopathological findings, such as hyperkeratosis, dyskeratosis with corps ronds and grains and papillary microvilli formation with suprabasal clefting. Despite its nearly constant histopathological presentation, unusual clinical variants are reported, such as the vegetating and cornifying ones. These variants share the same histopathological features of the classic type, except for the striking hyperkeratosis and acanthosis. Here, unreported pseudoepitheliomatous features are described in an elderly male patient with a long history of vegetating and verrucous papules and nodules of DWD, associated with typical nail involvement. These unique histolopathological changes were closely in conjunction with the characteristic microscopic features of DWD. Differential diagnosis with other pseudoepitheliomatous and acantholytic conditions such as reticulated seborrheic keratosis, inverted follicular keratosis, and acantholytic squamous cell carcinoma is also considered. Pseudoepitheliomatous features, in this case of vegetating DWD, could be regarded as a reactive epidermal phenomenon because of different stimuli, i.e. maceration, bacterial superinfection, and chronic scratching.