Line Field Confocal Optical Coherence Tomography ( <scp>LC</scp> ‐ <scp>OCT</scp> ) Features of Primary Cicatricial Alopecias

BACKGROUND: Primary cicatricial alopecias (PCA) are rare inflammatory disorders that irreversibly destroy hair follicles, making early, accurate diagnosis crucial. OBJECTIVE: The aim of this study is to describe line field confocal optical coherence tomography (LC-OCT) features of major PCA subtypes and assess its potential role in diagnosis and disease monitoring. METHODS: Twenty-five patients with PCA (lichen planopilaris [LPP], frontal fibrosing alopecia [FFA], folliculitis decalvans [FD], discoid lupus erythematosus [DLE], dissecting cellulitis of the scalp [DCS]) underwent LC-OCT imaging with vertical, horizontal, and 3D acquisitions of clinically and trichoscopically selected lesions. Images were independently evaluated to identify both shared and subtype-specific patterns. RESULTS: In active lesions of LPP/FFA (n = 15), infundibular hyperkeratosis with hyper-reflective keratinous sleeves was observed in 14/15 (93.3%), perifollicular bright inflammatory aggregates in 7/15 (46.6%), and dilated dermal vessels in 9/15 (60.0%). DLE (n = 4) was characterized by periadnexal inflammation, basal vacuolar alteration, and a continuous hyper-reflective junctional band in 4/4 (100%), dermal hyporeflective bands compatible with mucin in 2/4 (50.0%), and follicular plugs in 2/4 (50.0%). FD (n = 4) demonstrated tufted follicles with markedly dilated infundibula in 3/4 (75.0%), pustule-like hyporeflective cavities in 2/4 (50.0%), and periadnexal inflammatory infiltrates in 3/4 (75.0%). DCS (n = 2) showed superficial abscess-like lobulated hyporeflective cavities with perifollicular inflammatory clusters in 2/2 (100%) and follicular fusion with hair tufting in 1/2 (50.0%). In end-stage cicatricial areas, LC-OCT demonstrated follicular dropout with loss of sebaceous glands, dermal sclerosis forming a stellate pattern, and a flattened, hyper-reflective dermal-epidermal junction in all 25/25 cases (100%). CONCLUSIONS: LC-OCT identifies shared scarring signatures as well as distinct patterns among PCA subtypes, and it supports targeted biopsy site selection. Moreover, it provides a noninvasive tool for real-time assessment of disease activity that is complementary to trichoscopy and histopathology.