Alopecia areata (or loss of hairiness)
Alopecia areata differs from baldness, which results in hair loss (not body hair) for mainly hereditary reasons. On this subject, see our Alopecia sheet. |
Alopecia areata: what is it?
La alopecia areata causes a hair loss in patches, most often at scalp. The skin of the skull retains its normal appearance, but is simply devoid of hair in places. It is also called alopecia in plaques.
About 1% of North Americans are affected by alopecia areata. In almost half of the cases, symptoms appear before the age of 20. It represents 2% of dermatology consultations in France.
There is no cure for it. Certain treatments can stimulate regrowth hair. However, in almost 80% of people, hair reappears on its own 6 to 12 months after hair loss. The hair may even grow back years later. But nothing protects against a relapse (it is even frequent).
Causes
Scientists do not know what triggers the hair and body hair loss : viral infection, heredity, stress, exposure to a chemical. However, hereditary factors seem to play in 20% to 40% of people affected. The researchers speculate that the destruction mechanism involves an autoimmune reaction, where the antibody of the affected person would wrongly attack the hair follicles. The alopecia areata is also associated with the presence of other autoimmune diseases, such as vitiligo, type 1 diabetes, rheumatoid arthritis, discoid lupus and Hashimoto’s thyroiditis. Luckily, the stem cells in the hair follicles, which allow hair to grow back, remain intact. This explains why the hairs can start to grow again, even after several years of dormancy.
Evolution
The evolution of alopecia areata is quite unpredictable and very variable from one person to another. The majority of people will be cured after 1 year, but about 10% will be chronically affected and will have no hair regrowth.
Usually, alopecia areata remains localized to the scalp and is restricted to small, bare patches. Nevertheless, in its extensive form, it can progress and spread to the barbe and to everything scalp. Universal alopecia areata (loss of all body hair) is very rare.
In some individuals, the disease also attacks the nails : these take the form of a stopper and become marked at the tip, rough and dull.