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Alopecia Areata

Contributed by: Eman Bahrani, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030
  • Alopecia Areata (AA) is an uncommon disorder that affects 0.2% of the population and yields patchy non-scarring hair loss primarily affecting the scalp. The disease is chronic and often charts a relapsing remitting course. Treatment is primarily with topical or intralesional steroids.
Etiology and Pathogenesis
  • AA is an autoimmune disease and is associated with others such as Hashimoto Thyroiditis and vitiligo
  • Autoreactive T-cells that specifically target antigens within the hair follicle appear to be pathogenic, disrupting the normal hair cycle. Pathology shows a characteristic lymphocytic infiltrate around the hair bulb.
Diagnosis and Clinical Manifestations
  • AA manifests as a gradual loss of hair in discrete, round patches. Importantly, follicular markings are preserved, meaning AA is not associated with scarring. Exclamation mark hairs are characteristic, representing short, broken hairs with distal ends that are broader than the proximal ends. The scalp is affected most commonly, although the disease can in rare cases progress to include all body hair (alopecia universalis).
  • AA is a chronic disease that often remits spontaneously and then recurs.
  • Initial treatment often consists of topical application or intralesional injection of corticosteroids. There are a number of other therapeutic strategies but a new direction may be molecular targeting with JAK inhibitors. See Further Reading below.
Further Reading
  • Gilhar A, Etzioni A, Paus R. Alopecia areata. New England Journal of Medicine. 2012; 366:1515-1525.
  • Xing L, Dai Z, Jabbari A, et al. Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition. Nature Medicine. 2014;20:1043-9.