Line-Field Confocal Optical Coherence Tomography Criteria of Hair Follicles in Patients with Hidradenitis Suppurativa versus Healthy Controls

Introduction: Hidradenitis suppurativa (HS) is an inflammatory disease that leads to the formation of abscesses, fistulas, and scars primarily in the axillary, inguinal, and gluteal folds. While the exact pathophysiology is unclear, it is widely accepted that the hyperkeratinization of hair follicles plays a major role. Methods: Hair follicles of the axillary and inguinal folds of patients with HS and healthy controls were examined with line-field confocal optical coherence tomography (LC-OCT) in order to identify the morphological features of HS hair follicles. Results: Patients with HS (5 male, 6 female) with 42 examined follicles were compared to a control group of 16 patients (5 male, 11 female) with 67 follicular ostia. HS patients had a significantly larger mean diameter of the follicular opening (156 µm vs. 98 µm, p = 0.005). The border of the hair follicle was more frequently irregular (p = 0.005) and/or hyperreflective (p = 0.002). HS patients had more inflammatory cells around the hair follicle (p = 0.001). Furthermore, hyperreflective material in the infundibulum (p = 0.032) was more frequently observed. HS patients more often exhibited a perifollicular vessel dilatation (p = 0.026) and hypervascularization (p = 0.039). Increased epidermal thickness was also more prevalent (p = 0.001) in HS patients. Conclusion: The LC-OCT criteria for follicular ostia differed significantly between patients with HS and healthy controls. LC-OCT may therefore be helpful in the early diagnosis of HS, as well as in monitoring treatment. Further studies with larger sample sizes are necessary to examine the potential of LC-OCT in patients with HS.