Alopecia Areata

Alopecia areata is an idiopathic disorder characterized by the acute development of round or oval patches of hair loss (2-3 cm) without scarring of the scalp. It is estimated to affect 0.1 to 0.2% of the population at any time. Onset is usually in early adulthood. Patients are otherwise healthy. A family history is present in about 25% of cases. Hair elsewhere on the body may also be affected, including eyelashes, eyebrows, and beard. Nail pitting may be present, as well as other nail abnormalities. Alopecia areata is presumed to be an autoimmune disorder in with T lymphocytes react with antigens aberrantly expressed by hair follicle keratinocytes; several HLA associations are known. Several autoimmune diseases are associated with alopecia areata, including: atopic diathesis, thyroid disease, vitiligo, and inflammatory bowel disease.

Specific patterns of alopecia areata include:

Alopecia totalis. Complete loss of all scalp hair

Alopecia universalis. Complete loss of all body hair.

Ophiasis. A band of hair loss about the periphery of the temporal and occipital scalp.

Reticular. Recurrent disease, which may have areas of hair loss concurrent with areas where hair is beginning to regrow.

Diffuse. Widespread thinning, or limited to the vertex. Non-pigmented hair may be spared, leading to premature graying.

With what can alopecia areata be confused?

Alopecia areata should be distinguished from other forms of non-scarring alopecia, of which the main differentials are trichotillomania and tinea capitis. In trichotillomania the patches of hair loss have ill-defined margins. A KOH preparation and fungal culture can distinguish alopecia areata from tinea capitis.

Diffuse alopecia areata may resemble telogen effluvium or androgenetic alopeia.

How is alopecia areata diagnosed?

The acute onset of well-circumscribed round or oval patches of hair loss is consistent with a diagnosis of alopecia areata. Scarring is absent, though there may be some tenderness and erythema. A diagnostic finding is "exclamation point" hairs, which are short broken-off hairs that are narrower toward the scalp. Hairs can be removed with a hair pull test (6 or more hairs).

Histopathology. CD4+ lymphocytes and langerhans cells are seen in the peribulbar and perivascular areas, the external root sheath, and invading "follicular streamers". The lymphocytes around the lower potion of the follicle in early lesions is said to resemble a "swarm of bees". During active hair loss, an increased number of miniature follicles in telogen and catagen phase can be seen, but there is no loss of hair follicles. In advanced disease, early anagen and telogen follicles are affected. It is thought that the immune attack on the hair follicle forces follicles out of anagen, into catagen and then telogen, with shedding of the hair. In long standing disease, melanin incontinence, foreign body reaction, and trichomalacia may be observed.

How is alopecia areata treated?

Steroids are the mainstay of treatment, either topical, intralesional, or systemic. Immunotherapy is also used, including psoralens plus ultraviolet light A (PUVA), induction of allergic contact dermatitis with squaric acid, and cyclosporine. Topical or oral minoxidil is also used. Wigs are helpful for cosmetic reasons if hair loss is extensive.

What is the prognosis for alopecia areata?

A small percentage of patients may experience complete loss of all scalp (alopecia totalis) or body (alopecia universalis) hair; few patients with these conditions exhibit hair regrowth. For more confined disease, the prognosis is unpredictable. The majority of patients will have spontaneous hair regrowth, but the condition may recur. Poor prognostic factors are duration of hair loss of greater than one year, extensive areas of involvement, and an ophiasis pattern..

Image links

North American Hair Research Society: Fact Sheet and Photos on alopecia areata
Histopathology of Alopecia Areata from dermatology.org