Fibrosing alopecia in a pattern distribution: patterned lichen planopilaris or androgenetic alopecia with a lichenoid tissue reaction pattern?

BACKGROUND: Androgenetic alopecia is characterized by a defined area of progressive nonscarring alopecia. The clinical and histological findings in 15 women and 4 men with progressive scarring alopecia in a pattern distribution were studied. The results were evaluated and compared with clinicopathologic entities that feature scarring of the central scalp area, specifically, lichen planopilaris, pseudopelade, and follicular degeneration syndrome. OBSERVATIONS: Patients developed progressive fibrosing alopecia of the central scalp, without the multifocal areas of involvement typical of lichen planopilaris and pseudopelade. Perifollicular erythema, follicular keratosis, and loss of follicular orifices were limited to a patterned area of involvement. Biopsy specimens of early lesions demonstrated hair follicle miniaturization and a lichenoid inflammatory infiltrate targeting the upper follicle region. Advanced lesions showed perifollicular lamellar fibrosis and completely fibrosed follicular tracts indistinguishable from end-stage lichen planopilaris, pseudopelade, or follicular degeneration syndrome.
CONCLUSIONS: Some patients with androgenetic alopecia might have additional clinical and histological features of inflammation and fibrosis limited to the area of androgenetic hair loss. In these patients, the histological findings of early lesions are identical to those seen in lichen planopilaris. The lichenoid tissue reaction leading to follicular destruction in these patients might be pathogenetically related to the events underlying androgenetic alopecia.