In Vivo Microscopic Features of Acne vulgaris Revealed via LC-OCT

Acne vulgaris is a common skin disorder characterized by multifactorial pathogenesis. In recent years, multiple non-invasive imaging methods have been explored to monitor in vivo acne lesions. Technologies such as reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) have improved our capabilities to characterize and monitor this condition; nevertheless, limitations remain in resolution and depth. Line-field confocal optical coherence tomography (LC-OCT) is a novel imaging technique that combines the strengths of RCM and OCT, offering high-resolution vertical and horizontal imaging of skin tissue up to 500 µm deep. The aim of this study was to characterize and quantify the microstructural features of different acne lesion morphologies using LC-OCT and to compare these findings with those observed in normal skin.

A total of 52 facial acne lesions (microcomedones, closed and open comedones, papules, and pustules) from 20 patients with mild-to-moderate acne and 15 healthy controls were imaged using LC-OCT. Vertical, horizontal, and 3D images were analyzed for structural features, with quantitative measurements of lesion diameter and depth.

LC-OCT revealed distinct microstructural features at each stage of acne development. Microcomedones showed bright perifollicular rings in 83.3% of cases, absent in healthy skin, indicating early follicular hyper keratinization. Closed comedones appeared as cystic, keratin-filled structures beneath intact epidermis, while open comedones displayed surface discontinuities and mixed reflectivity plugs. Papules and pustules demonstrated perifollicular hyperreflective halos and numerous "bright dots", corresponding to inflammatory cell infiltrates.

LC-OCT provides non-invasive, high-resolution imaging of acne microarchitecture, from subclinical changes in acne-prone skin and incipient microcomedones to inflammatory lesions, offering potential utility in diagnosis, disease monitoring and personalized therapeutic strategies.