Facial Papules in Frontal Fibrosing Alopecia: Beyond Vellus Hair Follicle Involvement.

Background: Frontal fibrosing alopecia (FFA) is considered a variant of lichen planopilaris affecting mainly the frontotemporal hairline. Since the first report in 1994, several other clinical features have been associated with the disease, such as facial papules (FP). Even though FP have been linked to facial vellus hair follicle involvement, how this finding alone could lead to the formation of clinically evident FP in FFA patients had not yet been addressed.

Objective: To describe histopathological findings of FP in the context of FFA and to highlight features that may be linked to their clinical formation.

Methods: Cutaneous FP biopsies of FFA patients performed between January 2016 and May 2017 were retrieved from our pathology database and reexamined by 2 pathologists.

Results: Histological sections of thirteen 3.0-mm punch biopsy specimens (2 horizontally and 11 vertically oriented) were collected from 7 patients. Eleven specimens demonstrated prominent sebaceous glands and 10 dilated sebaceous ducts. Pinkus acid orcein staining revealed reduction and fragmentation of the elastic fibers in 12 samples and, in 7 of these, this finding was observed in both the papillary and reticular dermis, particularly around sebaceous lobules. Vellus hair follicle involvement was only seen in 2 samples.

Conclusions: Prominent sebaceous lobules with dilated ducts associated with an abnormal elastic framework seem to be the main explanation for the formation of FP in the context of FFA.