DYSKERATOSIS (G. dus- "abnormal," G. keratos ('horn," G. -sis ('condition")

Premature cornification ofindividual cells within the epidermis and epithelial structures of adnexa. Dyskeratotic cells have pyknotic nuclei and eosinophilic cytoplasm (Fig. 3.18) that, by electron microscopy, is seen to be packed with filaments of keratin in perinuclear aggregation. These prematurely cornified cells are encountered in inflammatory diseases such as Grover's disease and the verrucous stage of incontinentia pignlenti; in neoplastic diseases such as Bowen's disease and subungual keratoacanthoma; in genodermatoses such as Darier's disease; and in cystic conditions such as warty dyskeratoma. In all instances, dyskeratosis is an expression of the unexpectedly early, but slow, death of keratinocytes. Keratinocyies that die rapidly have no time to cornify, a fact made manifest by the presence of a normal basket-woven configuration of the stratum corneum above necrotic keratinocytes in conditions such as erythema multiforme and fixed drug eruption, and in those processes in which necrosis occurs even more rapidly and diffusely, e.g., burns of all kinds. Because slowly dying keratinocytes cornify abnormally, the stratum corneum above them is either parakeratotic or compactly orthokeratotic, as in Bowen's disease and lichen planus, respectively.