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Alopecia Areata
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Definition: Alopecia Areata (AA) is characterized by patches of hair loss that have well demarcated borders.
Description: AA initially affects small areas of the scalp. Then it may progress to cause complete loss of all scalp hairs and eyebrows (alopecia totalis) and of all body hairs (alopecia universalis). AA affects males and females equally and may occur at any age.
Treatment: A recent review of the treatment of AA can be read here.
Pathogenesis: AA is now considered an autoimmune disease. Originally the evidence for this was only circumstantial and included:
- infiltration of hair follicles by mononuclear cells, predominantly T lymphocytes, together with macrophages and Langerhans cells;
- strong family history;
- presence in the serum of antibodies directed against hair follicle antigens;
- presence in the same patient of other diseases whose autoimmune pathogenesis is more established (such as Graves’ disease, Hashimoto’s thyroiditis and myasthenia gravis);
- preferential usage of certain MHC class II alleles (such as DQB1*03 and DRB1*1104); and
- the beneficial effect of various immunosuppressive treatments.
In recent years, Dr. John P. Sundberg from the Jackson Laboratory (Maine) has characterized a mouse model that spontaneously develops a hair loss similar to the human AA. The autoantigen involved in the initiation of the disease, however, remains to be identified. A recent review on the pathogenesis of AA can be read here (reference).
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Links to other Resources:
www.naaf.org
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