Dermoscopy as a tool for rapid diagnosis of monilethrix.

Monilethrix is a rare cause of hair loss. We present a case of a 44-year-old female, in whom dermoscopy enabled a rapid diagnosis of monilethrix. Dermoscopy images in this patient showed hair shafts with uniform elliptical nodes and intermittent constrictions. Hairs were bended regularly at multiple locations and had a tendency to fracture at constriction sites. The diagnosis of monilethrix was confirmed by light microscopy. In a second patient hair shafts appeared irregularly constricted and had no tendency to bend or break, which was consistent with the diagnosis of pseudomonilethrix. We suggest the term "regularly bended ribbon sign" for describing the specific dermoscopic feature of monilethrix. It differentiates monilethrix from pseudomonilethrix and other causes of hair loss.