Evaluation of skin barrier function based on skin dermoscopic features in patients with rosacea

To the Editor: Rosacea is a common chronic inflammatory skin disease with typical manifestations such as flushing, erythema, papules, pustules, and phymatous changes.[1] It has been indicated that the resulting abnormal skin barrier structure and function was associated with the etiology and pathological process of rosacea.[2] Transepidermal water loss (TEWL) and stratum corneum hydration (SCH) are commonly used to evaluate skin barrier function and must be measured using specific instruments, such as the Cutometer MPA 580 and GPSkin Barrier® (GPOWER Inc., Seoul, South Korea), which inter-correlate well.[3] However, these instruments are not available to most dermatologists. Dermoscopy has been incorporated into the clinical practice of most dermatologists. Practically, dermoscopy is more accessible to clinical dermatologists than skin barrier measure instruments. Hence, we analyzed dermoscopic images as a skin barrier function evaluation method and compared the results with those of the GPSkin Barrier®, establishing the feasibility of dermoscopy as a skin barrier function evaluation method. Between January 2021 and November 2021, 119 patients with rosacea and Fitzpatrick skin type III to IV were enrolled in the study from the Dermatology Department of the First Affiliated Hospital of Nanjing Medical University. The study protocol was approved by the Ethics Committee Board of the First Affiliated Hospital of Nanjing Medical University (No. 2020-SRFA-082). All patients provided written informed consent. The key inclusion criterion was a clinical diagnosis of rosacea by two independent senior physicians according to the guidelines for rosacea. Participants underwent facial cleaning and acclimatization in an air-conditioned room under standardized conditions (22 ± 2°C, relative humidity 45 ± 5%) for 30 min prior to measurements. SCH and TEWL were measured on the malar skin using GPSkin Barrier according to the manufacturer's instructions. The data for every location was measured thrice and recorded. For TEWL values <10, the skin barrier was regarded as excellent; those between 11 and 19 indicated a good skin barrier; and those >20 reflected an impaired skin barrier. In terms of skin hydration, SCH values of 60 to 100, 30 to 60, and <30 indicated an excellent, good, and poor hydration status, respectively. Dermoscopic images were obtained at each skin barrier measurement site using a dermoscope (DermLite DL4, 3 Gen Inc., San Juan Capistrano, CA) in contact mode with both unpolarized and polarized lights. Two blinded dermoscopists scored the dermoscopic characteristics, including the presence of an erythemous background in the visual field (none = −2; <50% = −1; >50% = 0; Figure 1 A–C), the presence of a dermatoglyph (none = 0; some = 1; obvious = 2; Figure 1 D–F), and the presence of facial vellus hair or pores in the visual field (none = 0; <50% of the area = 1; >50% of the area = 2; Figure 1 G–I).Figure 1: The standard dermoscopic presentation of three characteristics, including erythemous backgroud by polarizad mode scored as –2 (A), –1 (B), and 0 (C), dermatoglyph by unpolarizad mode scored as 0 (D), 1 (E), and 2 (F), and facial vellus hair or pores by unpolarizad mode scored as 0 (G), 1 (H), and 2 (I).Statistical analysis was conducted using SPSS 20.0 software (SPSS Inc., Chicago, IL). Measured data are shown as mean ± standard deviation. The data according to the different groups were compared using chi-squared test. Statistical significance was assumed for P-values <0.05. Among the 119 patients, 19 had impaired skin barrier function (TEWL ≥20), 50 had good skin barrier function (TEWL 11–19), and 50 had excellent skin barrier function (TEWL ≤10). The correlations between TEWL and dermoscopic characteristics are shown in Supplementary Table 1, https://links.lww.com/CM9/B338. Statistically significant correlations were observed between the TEWL measurements and the erythemous background, dermatoglyph, and facial vellus hair or pores scores (all, P < 0.05). In total, 39 of the 119 patients were found to have poor skin hydration (SCH ≤30); 74 patients were found to have good skin hydration (SCH 31–59); and 6 patients had excellent skin hydration (SCH ≥60). The correlations between SCH and dermoscopic characteristics are shown in Supplementary Table 2, https://links.lww.com/CM9/B338. No statistically significant correlations were observed between SCH and the erythemous background, dermatoglyph, and facial vellus hair or pores scores (P > 0.05). Several studies have indicated that the skin barrier function is impaired in patients with rosacea, manifesting as significantly increased TEWL.[2] GPSkin Barrier® and MPA580 system are devices for evaluating TEWL and SCH that have proved to be inter-comparable and reliable.[3] However, these devices are not always available in clinical practice. On the other hand, dermoscopy is widely used in daily clinical practice worldwide, and is owned by the majority of dermatologists. In China, >380 articles about dermoscopy have been published in domestic or foreign journals from 2000 to 2019.[4] The easy accessibility of dermoscopy has made it a clinically useful tool for diagnosing rosacea. And also in some studies, dermoscopy has been used to evaluate the skin barrier changes caused by tape stripping.[5] Our study described the relationship between dermoscopic features and skin barrier function in patients with rosacea and provided a practical method that dermatologists can use to evaluate skin barrier status in these patients using dermoscopy only, which is to evaluate three characteristics, namely erythemous background, presence of dermatoglyph, and facial vellus hair or pores. The underlying mechanism might be more severe chronic inflammation in rosacea appearing as erythema, and destruction of the normal skin structure indicating more damaged skin barrier function appearing as the increased TEWL. TEWL might be a more precise indicator for the comprehensive assessment for skin barrier function constructed by epidermis and dermis together, while SCH mainly reflects the hydration status of stratum corneum, which might be the reason why it is not associated with the three characteristics revealed by dermoscopy in rosacea. Of course there are some shortcomings to using dermoscopic features to evaluate skin barrier function in patients with rosacea, especially as results may depend on the doctor's experience with dermoscopy. Yet this method has the potential to become widely used in practice, with no need to purchase new devices, and it is independent of the external environment. Meanwhile the visual images provide a long-term storage of information instead of single data, and provide a resource for repeated retrospective evaluations in the future. In conclusion, specific dermoscopic features could be used as indicators of skin barrier function in patients with rosacea, suggesting that these skin barrier function changes may be “visualized.” Conflicts of interest None.