Alopecia areata is a condition affecting humans, in which hair is lost from some or all areas of the body, usually from the scalp. Because it causes bald spots on the scalp, especially in the first stages, it is sometimes called spot baldness. In 1%–2% of cases, the condition can spread to the entire scalp (Alopecia totalis) or to the entire epidermis (Alopecia universalis).
The condition affects 0.1%–0.2% of humans, occurring in both males and females, though far more females than males. Alopecia areata occurs in people who are apparently healthy and have no skin disorder. Initial presentation most commonly occurs in the late teenage years, early childhood, or young adulthood, but can happen with people of all ages.
The most common type of alopecia areata involves hair loss in one or more round spots on the scalp.
- Hair may also be lost more diffusely over the whole scalp, in which case the condition is called diffuse alopecia areata.
- Alopecia areata monolocularis describes baldness in only one spot. It may occur anywhere on the head.
- Alopecia areata multilocularis refers to multiple areas of hair loss.
- The disease may be limited only to the beard, in which case it is called Alopecia areata barbae.
- If the patient loses all the hair on his/her scalp, the disease is then called Alopecia areata totalis.
- If all body hair, including pubic hair, is lost, the diagnosis then becomes Alopecia areata universalis.
Alopecia areata totalis and universalis are rare.
Alopecia areata is non communicable, or not contagious. It occurs more frequently in people who have affected family members, suggesting that heredity may be a factor. Strong evidence that genes may increase risk for alopecia areata was found by studying families with two or more affected members. This study identified at least four regions in the genome that are likely to contain alopecia areata genes. In addition, it is slightly more likely to occur in people who have relatives with autoimmune diseases. The condition is thought to be an autoimmune disorder in which the body attacks its own hair follicles and suppresses or stops hair growth. There is evidence that T cell lymphocytes cluster around these follicles, causing inflammation and