What condition is characterized by hair loss in circular patches?

Alopecia areata is a condition that is specifically characterized by hair loss occurring in circular patches. This autoimmune disorder causes the body’s immune system to mistakenly attack hair follicles, resulting in sudden, round areas of hair loss on the scalp or other parts of the body. Patients may experience complete scalp hair loss (alopecia totalis) or loss of all body hair (alopecia universalis) in more severe cases.

The distinction of alopecia areata from other forms of hair loss is significant. For instance, androgenetic alopecia, often referred to as male or female pattern baldness, involves a more gradual thinning of hair and does not present in circular patches. Tinea capitis, a fungal infection of the scalp, can cause hair loss but is usually associated with symptoms like scaling and inflammation rather than discrete patches. Traction alopecia results from continual tension on the hair and leads to gradual hair loss, particularly around the hairline, but does not present as isolated circular patches. Therefore, because alopecia areata is identified by its unique presentation of sudden and localized patchy hair loss, it is the correct answer to the question.