Fish against the Flow Sign: A Trichoscopic Pattern in Alopecia Areata of the Eyebrows

ABSTRACT

Trichoscopy has become an essential non-invasive tool for the diagnosis of alopecia areata, demonstrating characteristic features such as yellow dots, black dots, and exclamation mark hairs. Involvement of the eyebrows may present a diagnostic challenge because the short length and small calibre of eyebrow hairs make identification of these features less conspicuous than on the scalp. In this case series of five patients with eyebrow alopecia areata, a distinctive trichoscopic pattern was observed. Small exclamation mark hairs were seen interspersed among normal eyebrow hairs in an arrangement that visually resembled small fish swimming upstream against the flow of a river. This appearance, termed the “fish against the flow sign,” results from the reversed tapering of exclamation mark hairs compared with the natural architecture of normal eyebrow hairs. Recognizing this pattern may facilitate the identification of exclamation mark hairs during trichoscopic examination and assist in the diagnosis of alopecia areata affecting the eyebrows.