Trichoscopy of alopecia areata: An update.

The diagnosis of alopecia areata is usually based on clinical manifestations. However, there are several hair and scalp disorders that share similar clinical features with alopecia areata, such as tinea capitis, trichotillomania or traction alopecia. Trichoscopy as a fast, non-invasive and easy-to-perform technique may help to identify subtle details and establish the correct diagnosis. The aim of this review is to present the spectrum of trichoscopic findings in alopecia areata. A systematic review of the published work was performed by searching the PubMed, Scopus and EBSCO databases, complemented by a thorough hand search of reference lists. Of 427 articles retrieved, 30 studies were eligible for quantitative analysis. The reported features of alopecia areata were: yellow dots (6-100% patients), short vellus hairs (34-100%), black dots (0-84%), broken hairs (0-71%) and exclamation mark hairs (12-71%). Tapered hairs (5-81%) were reported in few studies, but a relatively high frequency of this finding in alopecia areata may indicate their important role in the differential diagnosis of hair loss. Rarely reported features, which include upright regrowing hairs (11-96%), pigtail (circle) hairs (4-61%) and Pohl-Pinkus constrictions (2-10%), may also be helpful in the diagnosis of alopecia areata. There is no pathognomonic trichoscopic marker for alopecia areata and the most common trichoscopic features are not the most specific. Therefore, the diagnosis should be based on the coexistence of several trichoscopic findings, not on the presence of a single feature.