Alopecia areata is a T lymphocyte-mediated autoimmune disease of the hair follicle resulting in nonscarring hair loss. Most cases are limited to 1 or 2 small patches of alopecia that involve the scalp, eyebrows, eyelashes, or body hair, but in severe cases, all hair on the scalp is lost (alopecia totalis) or all scalp and body hair is lost (alopecia universalis). History of sudden onset is characteristic.

Alopecia areata is seen equally in both sexes and in patients of all ages and races / ethnicities; however, it is most commonly seen in patients between the ages of 5 and 40 years. It is rarely reported in infants and even more rarely in the neonatal period, when congenital cases have also been reported. In a systematic review of 12 patients with congenital alopecia areata, 2 had alopecia totalis and 2 alopecia universalis. A family history of alopecia areata was present in 5 patients and nail changes in 3.

The course of alopecia areata in neonates and infants is not well studied. Spontaneous regrowth, stable disease over time and progression to alopecia totalis have all been reported. Treatment results and durability of response to treatment are variable.