Abstract
Frontal fibrosing alopecia (FFA) is an irreversible scarring alopecia with unknown etiology and no cure. The goal is to establish the diagnosis in the early stage, before developing a hairless band of atrophy involving the frontal, temporal scalp and sideburns. Pathology is rarely needed once the disease is clinically apparent. The classic histologic features include follicular dropout with the absence or atrophy of the sebaceous glands and lichenoid lymphohistiocytic infiltrate with concentric layered fibrosis at the upper follicular level. We describe a common pattern that was repeatedly seen in 6 horizontally sectioned scalp biopsies from patients with early presentation of FFA suspected on trichoscopy by the focal presence of peripilar casts around terminal hairs. All biopsies revealed overall preserved follicular architecture with average number of 11 vellus follicles, atrophy of the sebaceous glands, and perifollicular lymphohistiocytic infiltrate involving the outer root sheath of the vellus follicles (n = 5). There was no perifollicular fibrosis of the vellus follicles and no lichenoid inflammation and perifollicular fibrosis of the terminal follicles. This new pattern of "inflammatory vellus involvement" most likely corresponds to an early onset of the disease. The absence of the classic features in such biopsies from early FFA can lead to misdiagnosis.
