Cicatricial alopecia.

Scarring alopecias are of diverse etiology and pathogenesis. They may be histologically classified as primary or secondary, depending on involvement of reticular dermis. The most important primary scarring alopecias include pseudopelade, lichen planopilaris, and diffuse scarring of the vertex in African-Americans. The most important secondary scarring alopecias include folliculitis decalvans and late-stage lupus erythematosus.