Alopecia areata is a form of alopecia that impacts hair follicles, nails, and rarely, the retinal pigment epithelium and typically presents with round patches and is a type of non-scarring hair loss disorder characterized by loss of hair. Sometimes, this means simply a few bare patches on the scalp. In other cases, hair loss is more extensive. Although the exact cause is not known, this is thought to be an autoimmune disorder in which the immune system, the body’s defense system, mistakenly attacks the hair follicles, the tiny structures from which hairs grow. Unpredictable hair loss is the only noticeable symptom of this disorder. Regrowth of hair may or may not occur. Hair loss is usually confined to the head and face, although the entire body may be involved.
Scarring alopecia is divided into three major types:
- 1) Tinea capitis: the inflammatory variety of tinea capitis (favus) may culminate with scarring alopecia.
- 2) Alopecia mucinosa: This occurs when mucinous material accumulates in the hair follicles and the sebaceous glands. The mucinous material causes an inflammatory response that hinders the growth of hair.
- 3) Alopecia neoplastica: This is the metastatic infiltration of the scalp hair with malignant cells.
Non-scarring Alopecia
- Androgenetic alopecia
- Alopecia areata
- Telogen effluvium
- Traction alopecia
- Trichotillomania
- Anagen effluvium
Scarring Alopecia
- Alopecia mucinosa
- Metastatic infiltrate
- Favus
Symptoms
Alopecia areata often begins suddenly with oval or round bald patches appearing most commonly on the scalp. Other areas of hairy skin may also be involved. Gradually, the affected skin becomes smooth. New patches may spread by joining existing bald patches. These larger bald areas can appear while hair is regrowing in older hairless patches. Loss of hair can be permanent in some cases. Hair follicles may deteriorate, but oil-producing glands in the skin (sebaceous glands) usually change very little. The skin does not become hard or atrophied. In very few cases, all body hair may be lost. Cases beginning during childhood tend to be more severe than cases with an onset during adulthood.
The physical manifestations of this disorder may not be as difficult to handle for some individuals as the emotional ones. Most people with alopecia areata are generally healthy otherwise, and the disorder itself is not a sign of a serious or life-threatening disease.
Causes
The exact cause of alopecia areata is not known. An autoimmune mechanism is suspected in this disorder. Autoimmune disorders are caused when the body’s natural defenses against “foreign” or invading organisms (e.g., antibodies) begin to attack healthy tissue for unknown reasons. Some cases may be linked to abnormal reactions by blood cells (serum antibodies) to a thyroid protein (thyroglobulin), stomach (parietal) cells, or adrenal cells.
Recent genome-wide association studies (GWAS) metanalysis have localized the HLA signal of AA mostly to the HLA-DRB1. One locus harboring the genes that encode the natural killer cell receptor D (NKG2D) was implicated in AA and not in other autoimmune diseases, which suggests a key role in pathogenesis. Therefore, CD8+ NKG2D T cells have been a subject of study and found to be the major effectors in AA.[rx]
In 20 percent of cases, a familial pattern has been proposed, suggesting that some individuals may have a genetic predisposition to alopecia areata. A genetic predisposition means that a person may carry a gene for a disease but it may not be expressed unless something in the environment triggers the disease. It is not known whether this trigger comes from outside the body, such as a virus, or is internal. People who develop alopecia areata for the first time after age 30 are less likely to have other family members who also have the disorder.
The gene responsible for Alopecia Universalis (total absence of hair on the body) is located on the short arm of chromosome 8 (8p12).
Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females.
Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q”. Chromosomes are further subdivided into bands that are numbered. For example, chromosome 8p12 refers to band 12 on the short arm of chromosome 8.
Non-scarring alopecia falls into six major categories:
- 1) Alopecia areata: This is hair loss that can affect every part of the body, including the scalp, face, trunk, and extremities. When it affects only a portion of the body, it is called alopecia areata. When it affects an entire site, it is called alopecia totalis. When it involves the whole body, it is called alopecia universalis. The etiology is unknown, but it might be related to an autoimmune disease.[rx]
- 2) Androgenetic alopecia: is a pattern of hair loss that is affected by genes and hormones (androgenic).
- 3) Telogen effluvium: results from shifting of the hair cycle growth (anagen) phase towards the shedding (telogen) phase. It may result from an illness like hypo or hyperthyroidism. Also, it can arise from stress like major surgery. A crash diet, poor feeding, and drugs can cause telogen effluvium.[rx]
- 4) Traumatic alopecia: This is similar to traction alopecia, which results from forceful traction of the hair commonly seen in children. Also, trichotillomania is a type of traumatic alopecia in which the patient pulls on his/her hair repeatedly.[rx]
- 5) Tinea capitis: the classical kind of tinea capitis (black-dots) causes non-scarring hair loss, unlike other types like kerion and favus.
- 6) Anagen effluvium: This is hair shedding that occurs during the anagen phase of the cell cycle. Seen in cancer patients who are receiving chemotherapeutic agents.
Treatment
Treatment of alopecia areata is directed at producing regrowth of hair. Although there is no cure for alopecia areata at present, the hair may sometimes return by itself. In some cases, it may also fall out again after returning. The course of this disorder varies among individuals and is difficult to predict.
For mild, patchy alopecia areata, in which less than 50% of the scalp hair is gone, cortisone may be injected locally into areas of bare skin. These injections are done with tiny needles and are repeated once a month. Topical solutions, creams, and ointments may also help.
Triamcinolone acetonide 5-10 mg per milliliter given every 2 – 6 weeks, stimulates localized re-growth in 60 – 67% of cases.[rx] A study comparing different concentrations of intralesional triamcinolone acetonide (2.5 mg/ml, 5 mg/ml, 10 mg/ml) for the treatment of AA on the scalp, demonstrated similar rates of hair regrowth regardless of the concentration. However, the risk of cutaneous atrophy was higher at a higher concentration (10mg/ml).[rx] The use of intralesional betamethasone has been proposed, however, further studies are needed to evaluate its efficacy.[rx] Side effects include localized skin atrophy, pain, and depigmentation. Local skin atrophy might resolve within a few months. Relapses are frequent after cessation of treatment.
Potent topical glucocorticoids find frequent utilization in the treatment of alopecia areata; however, evidence of effectiveness is limited. Topical steroids can be a reasonable therapeutic option in patients unlikely to tolerate intralesional injections. Utilization of occlusive dressings confers a higher response, leading to improvement in greater than 25% of patients. Glucocorticoid-induced folliculitis is a relatively common adverse effect of this approach.[rx]
Patients with extensive disease, often defined as greater than 50% scalp hair loss, may be treated with topical immunotherapy. This approach avoids the large number of injections that would be otherwise required when using intralesional corticosteroids. Moreover, one retrospective study reported superior efficacy of topical immunotherapy over intralesional corticosteroids for patients with patches of hair loss exceeding 50 cm2 in size.[rx] A potent contact allergen such as diphenylcyclopropenone (DPCP) or squaric acid dibutyl ester (SADBE.) SADBE is applied weekly to the scalp to precipitate hair regrowth. Recently, a metanalysis looked at clinical outcomes of contact immunotherapy for alopecia areata.[rx] The rate of hair regrowth was 74.6% in the patchy alopecia subgroup, and 54.4% in the alopecia totalis/universalis subgroups. Recurrence rates were 38.2% in patients receiving maintenance treatment vs. 49% among those not receiving maintenance treatment.
Second-line therapies include minoxidil, anthralin, and PUVA.
Systemic therapies are generally only for patients with severe alopecia areata. Systemic glucocorticoids may induce hair growth. However, they are not widely used, mainly because of their side effects. Additionally, relapse occurs within a year in one-third of responsive patients, and the number of relapses increases with time. [rx] Other systemic therapies include methotrexate, cyclosporine, azathioprine, and etanercept, all of which have shown variable clinical responses.
Current investigational treatments include platelet-rich plasma, recombinant IL-2, hydroxychloroquine, JAK inhibitors (tofacitinib), simvastatin with ezetimibe, and excimer laser.[rx][rx][rx][rx][rx]
For more extensive alopecia areata, cortisone pills are sometimes given. However, these pills may have undesirable side effects that should be discussed with a physician beforehand.
Treatment tends to be less effective for more extensive alopecia areata than in cases of mild, patchy alopecia areata.
For cosmetic reasons, wigs and hairpieces may be necessary, especially for affected women and children.
References
Alexander Disease
