|Classification and external resources|
Alopecia areata, also known as spot baldness, is an autoimmune disease in which hair is lost from some or all areas of the body, usually from the scalp due to the body's failure to recognize its own body cells and subsequent destruction of its own tissue. Often it results in bald spots on the scalp, especially in the first stages. In 1–2% of cases, the condition can spread to the entire scalp (alopecia totalis) or to the entire skin (alopecia universalis).
There are two types: (1) scarring alopecia, where there is fibrosis, inflammation, and loss of hair follicles, and (2) nonscarring alopecia, where the hair shafts are gone but the hair follicles are preserved, making this type of alopecia reversible. Conditions resembling alopecia areata, and having a similar cause, occur also in other species.
Signs and symptoms
Typical first symptoms of alopecia areata are small bald patches. The underlying skin is unscarred and looks superficially normal. These patches can take many shapes, but are most usually round or oval. Alopecia areata most often affects the scalp and beard, but may occur on any part of the body with hair. Different areas of the skin may exhibit hair loss and regrowth at the same time. The disease may also go into remission for a time, or may be permanent. It is common in children.
The area of hair loss may tingle or be painful.
The hair tends to fall out over a short period of time, with the loss commonly occurring more on one side of the scalp than the other.
Exclamation point hairs, narrower along the length of the strand closer to the base, producing a characteristic "exclamation point" appearance, are often present.
When healthy hair is pulled out, at most a few should come out, and ripped hair should not be distributed evenly across the tugged portion of the scalp. In cases of alopecia areata, hair will tend to pull out more easily along the edge of the patch where the follicles are already being attacked by the body's immune system than away from the patch where they are still healthy.
Alopecia areata is thought to be a systemic autoimmune disorder in which the body attacks its own anagen hair follicles and suppresses or stops hair growth. For example, T cell lymphocytes cluster around affected follicles, causing inflammation and subsequent hair loss. A few cases of babies being born with congenital alopecia areata have been reported, but these are not cases of autoimmune disease, because infants are born without fully developed immune systems.
Alopecia areata is not contagious. It occurs more frequently in people who have affected family members, suggesting heredity may be a factor. Strong evidence of genetic association with increased 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 these genes. In addition, it is slightly more likely to occur in people who have relatives with autoimmune diseases.
In 2010, a genome-wide association study was completed that identified 129 single nucleotide polymorphisms that were associated with alopecia areata. The genes that were identified include those involved in controlling the activation and proliferation of regulatory T cells, cytotoxic T lymphocyte-associated antigen 4, interleukin-2, interleukin-2 receptor A, and Eos (also known as Ikaros family zinc finger 4), as well as the human leukocyte antigen. The study also identified two genes, PRDX5 and STX17, that are expressed in the hair follicle.
Alopecia areata is usually diagnosed based on clinical features.
Trichoscopy may aid in establishing the diagnosis. In alopecia areata, trichoscopy shows regularly distributed "yellow dots" (hyperkeratotic plugs), small exclamation-mark hairs, and "black dots" (destroyed hairs in the hair follicle opening).
A biopsy is rarely needed to make the diagnosis or aid in the management of alopecia areata. Histologic findings include peribulbar lymphocytic infiltrate ("swarm of bees"). Occasionally, in inactive alopecia areata, no inflammatory infiltrates are found. Other helpful findings include pigment incontinence in the hair bulb and follicular stelae, and a shift in the anagen-to-telogen ratio towards telogen.
- 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.
- Ophiasis refers to hair loss in the shape of a wave at the circumference of the head.
- The disease may be limited only to the beard, in which case it is called alopecia areata barbae.
- If the person loses all the hair on the 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.
If the affected region is small, it is reasonable to only observe the progression of the illness, as the problem often spontaneously regresses and the hair may grow back.
In cases of severe hair loss, limited success has been achieved by using the corticosteroids clobetasol or fluocinonide, corticosteroid injections, or cream. The cream is not as effective and it takes longer in order to see results. Steroid injections are commonly used in sites where the areas of hair loss on the head are small or especially where eyebrow hair has been lost. Whether they are effective is uncertain. Some other medications that have been used are minoxidil, Elocon (mometasone) ointment (steroid cream), irritants (anthralin or topical coal tar), and topical immunotherapy ciclosporin, sometimes in different combinations. Topical corticosteroids frequently fail to enter the skin deeply enough to affect the hair bulbs, which are the treatment target, and small lesions typically also regrow spontaneously. Oral corticosteroids decrease the hair loss, but only for the period during which they are taken, and these drugs can cause serious side effects.
In most cases which begin with a small number of patches of hair loss, hair grows back after a few months to a year. In cases with a greater number of patches, hair can either grow back or progress to alopecia areata totalis or, in rare cases, alopecia areata universalis.
There is no loss of body function, and effects of alopecial areata are mainly psychological (loss of self-image due to hair loss), although these can be severe. Loss of hair also means the scalp burns more easily in the sun. Patients may also have aberrant nail formation because keratin forms both hair and nails.
Hair may grow back and then fall out again later. This may not indicate a recurrence of the condition, but rather a natural cycle of growth-and-shedding from a relatively synchronised start; such a pattern will fade over time. Episodes of alopecia areata before puberty predispose to chronic recurrence of the condition.
The condition affects 0.1%–0.2% of the population, and occurs in both males and females. Alopecia areata occurs in people who are otherwise healthy and have no other skin disorders. Initial presentation most commonly occurs in the late teenage years, early childhood, or young adulthood, but can happen at any ages. Patients also tend to have a slightly higher incidence of conditions related to the immune system, such as asthma, allergies, atopic dermatitis, and hypothyroidism.
Many medications are being studied, including abatacept, MEXIS/M6S, triamcinolone, secukinumab, tralonkinumab, apremilast, botulinum toxin, INCB018424, bimatoprost, clobetasol, AS101, autologous platelet-rich plasma, topical minoxidil, and nitric oxide gel. Some of these medications are approved for other diseases, others are not available outside of studies.
In 2014, preliminary findings showing that oral ruxolitinib, a drug approved by the US Food and Drug Administration (FDA) for bone marrow disorder myelofibrosis, restored hair growth in three individuals with long-standing and severe disease. The medical costs almost USD $10,000 a month.
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