Alopecia Areata is a hair loss condition characterized by the rapid onset of hair loss in a sharply defined area. Any hair-bearing surface can be affected, but the most noticeable surface is the scalp. The reason alopecia areata occurs is not completely known. In some cases it is associated with other diseases, but most of the time it is not. Research is ongoing to determine the best treatment for this sometimes-striking disease.
Causes of Alopecia Areata
There are several different hypotheses as to what causes alopecia areata. Genetic factors seem to play an important role since there is a higher frequency of a family history of alopecia areata in people who are affected. Alopecia areata appears to also have an autoimmune factor causing the patient to develop antibodies to different hair follicle structures. Certain chemicals that are a part of the immune system called cytokines may play a role in alopecia areata by inhibiting hair follicle growth. Some studies show that emotional stress may also cause alopecia areata.
Hair loss occurs because the hair follicles in a discreet area all enter the telogen or late catagen stage of hair growth. In the catagen stage the hair follicle stops growing and in the telogen stage it falls out. Normally hairs are going through these stages at random and the growing hairs on the rest of the head outnumber the hairs that fall out. In alopecia areata, something causes all the hairs in a certain area to enter the telogen or catagen stage at the same time.
Appearance of Alopecia Areata
The characteristic patch of alopecia areata is usually round or oval, and is completely bald and smooth. "Exclamation-mark" hairs may be seen at the margin of the patch. These are broken, short hairs that taper at the base. Pulling slightly on these hairs causes them to fall out. Some people may experience a slight burning or tingling in the area of hair loss.
Prognosis of Alopecia Areata
The progress of alopecia areata is unpredictable. Some people lose hair in only a small patch. Others may have more extensive involvement. Alopecia totalis is the loss of 100% of scalp hair. Alopecia universalis is the loss of 100% of body hair. These last two conditions are rare. In the majority of patients, the hair will regrow completely within 1 year without any treatment.
Other Hair Loss Conditions
Other diseases that may be mistaken for alopecia areata include:
- Telogen effluvium - generalized hair loss caused by pregnancy, certain drugs, high fever, or stress.
- Androgenic alopecia - also known as male-pattern baldness.
- Trichotillomania - manually pulling the hair out caused by a psychological disorder.
- Secondary syphilis - causing a "moth-eaten" baldness pattern over the entire scalp.