What is alopecia areata?
The term alopecia means hair loss. In alopecia areata, one or more round bald patches appear suddenly, most often on the scalp. Alopecia areata is also called autoimmune alopecia.
Who gets alopecia areata?
Alopecia areata can affect males and females at any age. It starts in childhood in about 50%, and before the age of 40 years in 80%. Lifetime risk is 1–2% and is independent of ethnicity.
- A family history of alopecia areata and/or of other autoimmune conditions is present in 10–25% of patients.
- At least 8 susceptibility genes have been detected.
- Patients with alopecia areata have higher than expected rates of thyroid disease, vitiligo and atopic eczema.
- There is increased prevalence in patients with chromosomal disorders such as Down syndrome.
- It’s possibly drug-induced when arising in patients on biologic medicines
What causes alopecia areata?
Alopecia areata is classified as an autoimmune disorder. It is histologically characterised by T cells around the hair follicles. These CD8(+)NK group 2D-positive (NKG2D(+)) T cells release pro-inflammatory cytokines and chemokines that reject the hair. The exact mechanism is not yet understood.
The onset or recurrence of hair loss is sometimes triggered by:
- Viral infection
- Hormonal change
- Emotional/physical stressors
What are the clinical features of alopecia areata?
Several clinical patterns are described. More severe disease is associated with young age, concurrent atopic eczema, and chromosomal abnormalities.
Most patients have no symptoms, and a bald patch or thinning hair is noted incidentally, often discovered by a hairdresser. Other patients describe a burning, prickly discomfort in the affected areas—this is known as trichodynia.
Patchy alopecia areata
Patch alopecia areata can affect any hair-bearing area, most often the scalp, eyebrows, eyelashes and beard.
Patchy alopecia areata has three stages.
- Sudden loss of hair
- Enlargement of bald patch or patches
- Regrowth of hair
The bald areas may have a smooth surface, completely devoid of hair or with scattered “exclamation mark” hairs.
- Exclamation mark hairs are 2- to 3-mm in length, broken or tapered, with a club-shaped root. Microscopy shows a thin proximal shaft and normal caliber distal shaft.
- Regrowing hairs are often initially coloured white or grey; they may be curly when previously straight.
- It may take months and sometimes years to regrow all the hair.
- One patch can be falling out while another is regrowing.
- Affects up to 5% of patients with autoimmune hair loss
- All or nearly all scalp hair is lost
- Affects less than 1% of cases
- All hair or nearly all hair on the entire body is lost
- Pattern of alopecia areata affecting occipital and lateral scalp
- Bald area can encircle scalp
Diffuse alopecia areata
- Sometimes called alopecia areata incognita
- Presents with sudden diffuse thinning of scalp hair
- Persisting hair tends to grey, thus descriptions of 'turning white overnight'
- Positive hair pull test
- May be confused with telogen effluvium or hair loss due to medications
Alopecia areata of the nails
Complications of alopecia areata
Alopecia areata patients are at risk for psychosocial consequences of their disease, such as depression and anxiety.
They should be assessed for atopy, vitiligo, thyroid disease, and other autoimmune conditions.
How is alopecia areata diagnosed?
Alopecia areata is diagnosed clinically. Although usually straightforward, additional tests are sometimes needed to confirm the diagnosis.
What is the treatment for alopecia areata?
There is not yet any reliable cure for alopecia areata and other forms of autoimmune hair loss. Because spontaneous regrowth is common in alopecia areata, and research has often been of poor quality, the effectiveness of reported treatments is mostly unknown.
Several topical treatments used for alopecia areata are reported to result in temporary improvement in some people. The hair falls out when they are stopped. These include:
Intralesional corticosteroid injections
Injections of triamcinolone acetonide 2.5–10 mg/ml into patchy scalp, beard or eyebrow alopecia areata may speed up regrowth of hair. Its effect is temporary. If bald patches reappear, they can be reinjected.
Oral and pulse intravenous steroids in high dose can lead to temporary regrowth of hair. Most physicians agree that long-term systemic steroid treatment is not justified because of potential and actual adverse effects.
The sensitizing agents diphenylcyclopropenone (diphencyprone) and dinitrochlorobenzene provoke contact allergic dermatitis in treated areas. These sensitisers can be reapplied once weekly to bald areas on the scalp. The resultant dermatitis is irritating and may be unsightly. It is often accompanied by a swollen lymph gland.
A combination of the lipid lowering agents simvastatin and ezetimibe (which have immunomodulating effects) has been reported to be effective.
Several patients with severe alopecia areata have had improvement when treated with oral tofacitinib or oral ruxolitinib, which are Janus kinase (JAK) inhibitors. It is thought they may act by blocking interleukin (IL)-15 signalling. Watch out for the results of clinical trials of these biologic medicines.
What else should be considered for alopecia areata?
Some people with alopecia areata seek and benefit from professional counselling to come to terms with the disorder and regain self-confidence.
Camouflaging hair loss
A hairpiece is often the best solution to disguise the presence of hair loss. These cover the whole scalp or only a portion of the scalp, using human or synthetic fibres tied or woven to a fabric base.
- A full wig is a cap that fits over the whole head.
- A partial wig must be clipped or glued to existing hair.
- A hair integration system is a custom-made hair net that provides artificial hair where required, normal hair being pulled through the net.
- Hair additions are fibres glued to existing hair and removed after 8 weeks
Styling products include gels, mousses and sprays to keep hair in place and add volume. They are reapplied after washing or styling the hair.
Artificial eyelashes come as singlets, demilashes and complete sets. They can be trimmed if necessary. The lashes can irritate the eye and eyelids. They are stuck on with methacrylate glue, which can also irritate and sometimes causes contact allergic dermatitis.
Eyeliner tattooing is permanent and should be undertaken by a professional cosmetic tattooist. The colour eventually fades and may move slightly from the original site. It is extremely difficult to remove the pigment, should the result turn out to be unsatisfactory.
Artificial eyebrows are manufactured from synthetic or natural human hair on a net that is glued in place.
Eyebrow pencil can be obtained in a variety of colours made from inorganic pigments.
Tattooing can also be undertaken to disguise the loss of eyebrows, but tends to look rather unnatural because of the shine of hairless skin.
How can alopecia areata be prevented?
We do not yet know how to prevent the onset of alopecia areata.
What is the outlook for alopecia areata?
In 80% of patients with a single bald patch, spontaneous regrowth occurs within a year. Even in the most severe cases of alopecia totalis and alopecia universalis, recovery may occur at some future date.
Poor prognostic factors include:
- Extensive disease
- Bald patches persisting for more than 1 year
- Ophiasis pattern of hair loss
- Alopecia areata of the nails
- Onset of alopecia areata before puberty
- Family members with alopecia areata
- Personal or family history of other autoimmune diseases
- Down syndrome
New monoclonal antibody biologic agents targeting cytokine pathways offer promise for future treatment of alopecia areata.