Keratosis pilaris atrophicans is a group of fairly esoteric disorders. This particular patient has keratosis folliculitis spinulosa decalvans, a subtype which clinically shows generaized keratosis pilaris with facial and scalp follicular atrophy, plugging and alopecia. Biopsies from the keratosis pilaris region are indistinguishable from idiopathic keratosis pilaris, i.e. follicular plugging with dense keratinization and elevation of the plug over the epidermal contour. This biopsy was from the scalp during an active phase of the disease. These histologic findings show overlap with the folliculopustular processes like dissecting cellulitis or folliculitis Decalvans, and will eventually lead to a cicatricial alopecia.
A low power image shows a dense inflammatory infiltrate with distorted follicles and extruded hair shafts. The epidermis is breaking down.