Cicatricial (scarring) alopecias
Introduction Cicatricial (scarring) alopecia represents a diverse group of diseases characterized by lack of follicular ostia (Figure 7.1) and irreversible alopecia. The terms cicatricial and scarring are used interchangeably. A basic knowledge of follicular anatomy is important in the understanding of scarring alopecias, because the location of the inflammatory infiltrate is crucial in determining irreversibility of alopecia. Follicular stem cells are located in the bulge area where the arrector pili muscle inserts into the follicles. These cells migrate down into the
hair follicle, and subsequently differentiate into the various layers of the hair follicle. As the hair cycles through anagen, catagen, and telogen, there is a permanent upper portion of the hair follicle and a non-permanent lower portion, (see Chapter 1, Figure 1.8). When the inflammation is located deep, in the vicinity of the non-permanent portion, a scarring alopecia is unlikely to develop. If the inflammation is located within the permanent portion, particularly around the stem cells of the bulge area and the infundibulum, then a cicatrizing alopecia is more likely to occur. Follicles can be saved from irreversible damage if this peribulge infiltrate can be controlled. Scarring alopecias are true trichologic emergencies.