Alopecia Areata

Alopecia areata

Alopecia areata (AA) is the patchy loss of hair on the scalp or body. It can occur at any age and affects 1% of the population, most commonly children. The reasons for its development are not fully understood. Although not life threatening, the hair loss can be psychologically traumatic.

Scientists think AA is an autoimmune disease where white blood cells from the immune system attack hair follicles and keep them from producing hairs. Autoimmune disease occurs when a patient's immune system mistakenly thinks that part of his or her own tissue is diseased. The tissue is then attacked. The end result depends on how effectively the tissue defends itself as it tries to grow back normally.

Usually, dermatologists diagnose AA by close examination of the scalp, and considering, then eliminating other hair loss causes. Typical AA starts as a smooth bald patch that suddenly appears. Some people feel a tingling sensation or very mild pain in the affected area. The scalp is the most commonly noticed area, but AA can form anywhere on the body: eyelashes, armpits, leg hairs, etc.

AA spreads out on the edges as it grows, with the hairs on the edges thinning out at the roots until they fall out. The stubble left at the edge is thin at the bottom and is said to look like an exclamation mark (!). As long as hair can be easily pulled out, the AA is active and further hair loss should be expected. More hair in the comb means more spots.

Not all cases are obvious, and in these the dermatologist must take a small skin biopsy plug (a small piece of skin less than a 1/4 inch in diameter) for microscopic examination. Habitual hair pulling (trichotillomania), scalp fungus (black-dot ringworm) and other skin diseases (lichen planopilaris, cutaneous lupus and telogen effluvium) cause the most confusion.

Most cases that start with a few patches last a few months to a year and normal hair growth quickly resumes. If there are more than a few small patches of hair loss, it may also grow back or develop into total scalp hair loss (alopecia totalis) or even complete body hair loss (alopecia universalis), although this is rare. Severe disease has less of a tendency to resolve on its own, especially in children or atopic (prone to allergy) individuals.

AA is unpredictable, and repeated episodes are not unusual. Some cases last many years with some regrowth in one area, while at the same time new areas appearing. AA may also cycle through expression and remission. When hair does start to regrow, it tends to be of very fine "peach fuzz" hair, eventually regaining most or all of its normal color and texture.

There is no actual loss of hair follicles (i.e. the "root") even in the hairless lesions. The follicles are not producing visible hairs because of the attacking white cells that surround the root. Hair follicles are capable of taking a lot of punishment. Despite the attack by immune cells the hair follicles usually remain capable of re-growing even after years of attack. However in severe cases this becomes less and less likely as years pass.