Follicular Porokeratosis of the Scalp: First Description of Clinical and Trichoscopic Features

Porokeratosis (PK) is an epidermal disorder of keratinization, caused by a clone expansion of a mutated keratinocyte that generates a thin parakeratotic column: the cornoid lamella (CL). Depending on the clinical presentation, we differentiate up to 6 different types of PK. Most frequent locations for the lesions are limbs and trunk, while scalp is rarely affected. The possible origin of the CL in the epidermal appendages has been proposed (ostia of the eccrine glands and infundibulum of the follicle). The first case of PK limited to the scalp with exclusive involvement of the hair follicles is presented in this manuscript. It helps identify the clinical description and especially the trichoscopy as a diagnostic key in follicular PK and also to elucidate if it is an incidental histological finding or a new different clinical variant of PK.