PATHOGENESIS OF ALOPECil AREATA

Abstract

Alopcia areata (AA)is a common, emotionally distressing, inflammatory disorder of the hair.This non scaning alopecia accounted for about 2 to 3% among the dermatoses and 0.1% in the population at large.AA is equally common in patients of both genders and can affect . people of any age. lt is more frequent in children and young adults. Although it is usually limited to patches on the scalp, it may involve the entire scalp and other hair-bearing regions of the body. Alopecia areata may be also associated with atopy, down syndrome, emotional Stress,foci of sepSIS and cytomegaloVirus (CMV)infection. Alopecia areata may be characterized by the sudden precipitation of anagen follicles into early catagen at the site of disease activity. Numerous studies outlined the major histopathologic changes in AA, which included lymphocytic infiltration of the matrix and outer foot sheath (ORS) of the hair bulb, edema of the dermal papilla (DP),rupture of the basal lamina (BL), separating the matrix and the DP,catagen like DP and autophagic vacuolization of the hair bulb cells. Indirect confirmation of AA is the presence of exclamation-mark hairs (EMH),which appeared to result from injury to precortical keratinocytes and occmTed in areas of acute hair loss. A striking clinical feature of AA is that white hair is commonly spared and that regrowth is often initially white which suggested the involvement to some extent of the hair bulb melanocytes in the etiology ofAA.