Focal acantholytic dyskeratosis occurring in pityriasis rubra pilaris.

Focal acantholytic dyskeratosis (FAD) is a distinctive histologic pattern characterized by suprabasilar clefts surrounding dermal papillae (villi), acantholytic and dyskeratotic cells at all levels of the epidermis, hyperkeratosis, and parakeratosis. The features of FAD are typically seen in Darier's disease, warty dyskeratoma, and transient acantholytic dermatosis; they are also present in a variety of cutaneous neoplastic and nonneoplastic lesions. FAD, however, has not been previously described in lesions of inflammatory dermatoses. We report a case of FAD occurring in lesions of pityriasis rubra pilaris (PRP). To the best of our knowledge, this is the first reported case of this kind. We also review the pertinent literature.