Topographical Difference in the Prognosis of Alopecia Areata.

Abstract

Dear Editor: Although macroscopic clinical parameters such as disease duration, extra-scalp hair loss, and extent of hair loss can be used as prognostic markers for alopecia areata (AA), these factors have limitations in directly explaining the localized shortterm course of individual alopecia patches. The inf luence of regional factors on the course of AA is unclear due to the randomness of occurrence and chronic relapsing course. This study aimed to evaluate the clinical characteristics and prognosis of AA according to the area affected. This retrospective analysis included patients with AA who visited Wonju Severance Christian Hospital from March 2013 to February 2020. Among patients, individuals with alopecia patches were analyzed using Olsen/Canfield SALT (Severity of Alopecia Tool) score. Olsen/Canfield SALT was divided into top, posterior, and lateral areas, so we arbitrarily divided it into four areas (frontal, temporoparietal, vertex, and occipital) to determine the correlation with the anatomical location region in more detail. Involving only one of the four areas within the scalp were included in the analysis. The patients were divided into four groups according to the affected area. Demographic data including age, sex, disease duration, initial extent of hair loss, and presence of extra-scalp hair loss were compared between groups. The prognosis and recurrence between groups were analyzed using the Kaplan-Meier method. This study was approved by the institutional review board of Wonju Severance Christian Hospital (CR317095). A waiver of informed consent was granted owing to the deidentified data used. No clinical variables, except age and sex, were significantly different between groups (Table 1). On cumulative incidence analysis, there was significant difference between groups with regard to complete hair regrowth (>90% hair regrowth compared to initial extent) unlike major hair regrowth (>60% hair regrowth compared to initial extent) (Fig. 1). In particular, the difference in prognosis between groups was found to be more noticeable with long-term treatment. Although the recurrence rate was the highest in the temporoparietal group, there was no difference between groups in the survival analysis of hair loss after achieving hair regrowth (Supplementary Fig. 1). Differences in the anatomical structure, vascularity, and innervation are involved in topographical differences of AA. Recently, based on the relationship between mechanical stress and autoimmunity in the skin or other organs, it has been speculated that site-specific activation of mechanical stress may induce regional differences in autoimmunity. Differences in mechanical properties according to the scalp regions have been experimentally proven, extending beyond numerical differences in terminal hair or hair follicle units. These differences would provide another clue in explaining topographic differences in AA. However, it is unclear whether these stresses or differences in intrinsic properties lead to selective dysregulation of immunity around hair follicles. The study has few disadvantages. It is a single institutional study including a small number of samples of only mild-tomoderate AA cases involving only one of the four areas within Brief Report Annals of Dermatology 2023;35(3) • https://doi.org/10.5021/ad.20.329