Color-Transition Sign: A Useful Trichoscopic Finding for Differentiating Alopecia Areata Incognita from Telogen Effluvium

In the 2018 letter to the editor, the authors described the "color-transition sign" as a useful trichoscopic finding for differentiating alopecia areata incognita (AAI) from telogen effluvium (TE). They presented a case of a 1-year-old Japanese girl with diffuse hair loss without visible alopecic patches, where trichoscopy revealed a substantial number of hair shafts with a brighter brownish color at their proximal portion, indicating a long-standing assault on hair follicles. This sign, characterized by color graduation from black to clear between the distal end and the proximal root of the hair shaft, was distinct from the natural proximal depigmentation seen in TE. The authors suggested that the color-transition sign could help in the non-invasive distinction of AAI from TE, which is important for better management of this unusual subset of AA. They acknowledged that further case accumulation is necessary to confirm the utility of this sign.