Author Affiliation: Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, Florida.
I agree with Camacho in that it is common to see hairs that are spared by the inflammatory process in all types of cicatricial alopecias. However, the term lonely hair sign describes the presence of one or few isolated terminal hairs in the middle of the forehead. This sign is specific for frontal fibrosing alopecia, the only cicatricial alopecia characterized by progressive recession of the frontotemporal hairline. The lonely hairs are single, not grouped in tufts, and are commonly seen in untreated patients. At dermoscopy, the lonely hair is seen to be not affected by peripilar erythema or scales, but its surrounding skin shows loss of follicular openings typical of established scarring alopecia. The lonely hair sign is helpful to clinically distinguish frontal fibrosing alopecia from other conditions that can cause frontotemporal hair loss such as traction alopecia, androgenetic alopecia, or alopecia areata.
Tosti A. Lonely Hair Sign: Not Specific for Frontal Fibrosing Alopecia—Reply. Arch Dermatol. 2012;148(10):1208-1209. doi:10.1001/archdermatol.2012.1873