ABSTRACT
DEFINITION AND CLINICAL FEATURES A chronic non-scarring autoimmune disorder affecting the hair follicle. Typically, there is a sudden onset of solitary or multiple circular or oval bald areas, usually affecting the scalp (192) but any hair-bearing area may be affected. The residual hair follicles are visible confirming a lack of scarring. Diagnostic exclamation mark hairs may be visible at the margins of the lesion. The affected scalp is usually normal in colour but may be erythematous. Hairs at the edge of the patch may be easily removed with gentle traction. Spontaneous regrowth frequently occurs, but the areas may spread peripherally and may eventually involve the whole scalp (alopecia totalis) and even facial (193) and body hair (alopecia universalis). Rarely, a diffuse alopecia may occur without discrete bald patches. Regrowing hairs are usually white. Nail changes may also occur, particularly in extensive disease, as fine regular pitting or a roughened, sandpaper appearance (trachyonychia) (194). Alopecia areata is a common disorder affecting all races and either sex equally. It occurs at any age, with the highest incidence between 10 and 30 years.
