Follicular microhemorrhage: a unique dermoscopic sign for the detection of coexisting trichotillomania in alopecia areata.

The diagnosis of trichotillomania (TT) is often difficult as it presents similar clinical manifestations with other hair loss diseases, especially alopecia areata (AA). As TT often coexists with AA, the methodology enabling reliable detection of TT in AA needs to be developed. Recently, characteristic dermoscopic findings of TT have been reported, yet, they were most clearly detectable by conventional immersion dermoscopy, not by dry dermoscopy, a technique more easily adoptable in daily practice. In addition, the usefulness of those signs for differentiating TT from AA has not been sufficiently assessed. Through intensive scanning of hair loss lesions by dry dermoscopy in AA patients with TT, we found a sign potentially useful for detecting hidden TT. The sign we named "follicular microhemorrhage" (FMH) represents a red dot corresponding to a follicular ostia capped or stuffed with blood clot and suggests a history of traumatic forced plucking. So far, we have detected FMH in four TT patients with moderate to severe AA. Although further accumulation of cases is necessary, FMH would be beneficial to dissect complicated pathophysiology of hair loss in AA patients with TT.