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Androgenetic Alopecia

Androgenetic Alopecia1

Androgenetic Alopecia2


General Information

Androgenetic Alopecia (AA) or common baldness is essentially a cosmetic disorder. The disorder is significant only in that it allows ultraviolet light to reach the scalp and, thus, increasing the amount of actinic damage. The scalp has a 3-phase cycle of hair with almost 90% of hair in the anagen (growth) phase which may last up to 2-6 years, 1 % in the catagen phase which may last 3 weeks, and 10% in the telogen (resting) phase which may last 3 months. Patients have a reduction in the terminal-to-vellus hair ratio, normally at least 2:1. Following miniaturization of the follicles, fibrous tracts remain. Patients with this disorder usually have a typical distribution of hair loss. The onset of the disorder is genetic and gradual with males thinning in the temporal areas and females thinning on the crown. Only two proven FDA approved medications are currently available for treatment of AA: Minoxidil and Finasteride. Minoxidil is applied topically and available as 2% or 5% solutions. Finasteride is taken orally.

Epidemiology
Affects 50% of males by age 50, and 40% females by age 70 or over

Etiology
Genetically determined condition

Pathogenesis
Transition from large, thick, pigmented terminal hairs to thinner, shorter, indeterminate hairs and finally to short, wispy, nonpigmented vellus hairs in the involved areas is gradual.

Clinical
In males frontal and vertex thinning and eventually an area of denudation. In females usually a diffuse thinning on the crown.

Histology
Focal basophilic degeneration of the connective tissue sheath of the lower one-third of otherwise normal anagen follicles.

Bibliography
1. “Androgenetic alopecia “(Online) June 2005. http://www.e-ijd.org/article.asp?issn=0019-5154;year=2005;volume=50;issue=4;spage=179;epage=190;aulast=Thomas (visited: March 13, 2008) 2. “Androgenetic alopecia ” (Online) August 2007. http://www.emedicine.com/derm/topic21.htm (visited: March 13, 2008) 3. Weeden, David AO, MD, FRCPA Skin Pathology, Second Edition Churchill Livingstone 2002.

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