Alopecia areata is characterized by sudden, usually circumscribed, hair loss, most typically in round or oval patches on the scalp. Other clinical patterns include ophiasis hair loss (bands of hair loss at the scalp margins), inverse ophiasis pattern (loss of hair on the crown with retention of hair along the scalp margins), alopecia totalis (loss of all scalp hair), alopecia universalis (loss of all scalp and body hair), and the uncommon diffuse alopecia areata, manifested by diffuse thinning without discrete areas of hair loss (although tiny discrete areas can sometimes be found on careful examination). A middle-aged patient with diffuse alopecia areata may complain ofrapid graying as the pigmented hairs are often preferentially lost in alopecia areata.
Alopecia areata is a fairly common condition, with a lifetime incidence of 1-2 %. It affects males and females equally. Its onset can be at any age from infancy to old age, 60% of patients develop the condition by age 20. The course of the condition is completely unpredictable. Most patients do develop more than one area of alopecia in their lifetime. Areas of hair loss come and go over the patient’s lifetime. There may be days, months, years or even decades between times of hair loss. Most areas of hair loss spontaneously regrow, however the regrowth may take months to a couple years. Hair loss in the ophiasis areas is slower to regrow and sometimes does not occur, even with successful treatment of other areas on the same patient’s scalp. Treatment of alopecia areata only speeds up the expected regrowth. Treatment does not change the natural history of the condition and can not be used to prevent new areas of hair loss from occurring.