- Group of disorders which are all characterized clinically by lesions that are surrounded by a fine thread-like ring corresponding to the cornoid lamella seen histologically
- Clincal variants include: porokeratosis of Mibelli, superficial disseminated porokeratosis, linear porokeratosis, porokeratosis punctata palmaris et plantaris and disseminated superficial actinic porokeratosis.
- Associated with immunosuppression
- Increased risk of devloping squamous cell carcinoma
- Cornoid lamella: an isolated column of parakeratosis, usually oriented obliquely to the epidermis, arising from a pit-like area of attenuated epidermis
- Absent granular layer subjacent to the cornoid lamella
- In a biopsy taken to include both sides of an annular lesion, two cornoid lamellae are typically seen, one at each end of the specimen, with the superficial end of each lamella pointed toward the center of the specimen.