Definition and Incidence
Alopecia areata is a chronic inflammatory condition affecting hair follicles, resulting in discrete areas of hair loss. The separate patches may coalesce to form larger areas. The most commonly affected site is the scalp, but in rare cases the whole body may be affected – called alopecia universalis.
Alopecia occurs in approximately one per thousand persons, affecting men and women equally. Most patients are below the age of 30 at the onset. Most cases resolve spontaneously, though recurrence is common.
Possible causes and associated conditions
There is no single definite known cause for alopecia, but the most accepted explanation is that it is an auto-immune condition. Antibodies to hair follicles are frequently present in affected persons: these attack and temporarily damage the follicles, preventing further hair growth.
There is an association with other auto-immune diseases, such as thryoiditis, vitiligo and pernicious anaemia.
Up to 20 percent of patients have a family history of alopecia, which suggests a genetic predisposition.
Regardless of the genetic or auto-immune status, it is possible that a triggering event is required to initiate the episode of alopecia. Trigger factors which have been proposed include:
- stress – especially sudden, severe emotional stress
Symptoms, signs and diagnosis
The diagnosis of alopecia is primarily clinical, that is, based on the findings at examining the patient. The hairless patches are typically painless, smooth and circular, with short broken hairs around the edges. The nails may also be involved, with roughening and pitting. Rarely, the eye may be affected, with the onset of early cataract.
Biopsy of affected sites is rarely needed.
Blood tests may be done to establish whether there are any underlying auto-immune conditions which may have precipitated the alopecia, and which themselves need treating.
Other conditions causing hair loss may be considered, and can usually be excluded on examination. Some of these are:
- cicatricial alopecia – this rare condition permanently destroys the hair follicle, so that hair regrowth is impossible;
- tinea capitis – a fungal infection of the scalp, causing scaly patches;
- trichotillomania – nervous hair-pulling; and
- androgenic alopecia – male-pattern baldness, causing gradual thinning rather than patches of sudden hair loss.
Treatment and outcome
Most patients do not require treatment, as up to 80 percent who have limited alopecia will have spontaneous hair regrowth over several months. A minority may take several years to return to normal, and in some patients the hair never regrows. The prognosis is worse for patients with large areas of hair loss. Many patients will also experience relapses.
Treatment usually speeds up recovery, but does not cure the condition, and the patient may relapse in the future. Treatment options include
- Steroids – injected into the bald patches every four to six weeks until hair regrowth is complete. Results may be visible within a month of starting the course of injections. The skin may need pretreatment with anaesthetic cream, as the injections may be painful. Topical steroids (applied to the skin) have had limited success.
- Minoxidil – this is a non-prescription solution, which is applied to the scalp twice daily, and may be used together with steroids. In combination, results may be seen within twelve weeks, but it has little effect in severe or widespread alopecia.
- Immunotherapy – may be considered for extensive alopecia. A substance known to cause a strong allergic reaction is applied to the skin; the resulting irritation can induce new hair growth, though the mechanism of this is not understood. This type of treatment should only be undertaken by a specialist dermatologist.
- Phototherapy – here a patient is given a light-sensitive drug, then exposed to ultraviolet light. Treatment last four to six months. Conflicting results have been reported. Phototherapy is thus only considered for patients with extensive alopecia when immunotherapy is contraindicated or unacceptable. Because some of the sensitising drugs remain in the body for a long time, patients may still have to avoid exposure to sunlight for weeks after completing treatment.
- Cosmetic – wigs are considered usually by women who have extensive scalp alopecia, especially if it persists for a long time.
(Dr AG Hall, Health24, January 2008)