Primary cicatricial alopecias (PCA) are a rare group of disorders in which the hair follicle is the main target of destructive inflammation resulting in irreversible hair loss with scarring of affected lesions. Inflammation may predominantly involve lymphocytes or neutrophils. Cicatricial alopecias that mainly involve lymphocytic inflammation include lichen planopilaris, discoid lupus erythematosus, pseudopelade (Brocq), central centrifugal alopecia, alopecia mucinosa, and keratosis follicularis spinulosa decalvans. Cicatricial alopecias that are due to predominantly neutrophilic inflammation include folliculitis decalvans and dissecting cellulitis of the scalp. Acne keloidalis, acne necrotica, and erosive pustular dermatosis are cicatricial alopecias with a mixed inflammatory infiltrate.
Part of the book: Hair and Scalp Disorders