Abstract: 【Abstract】 Objective To investigate imaging characteristics of papulopustular rosacea （PPR） by high-frequency ultrasound combined with color Doppler flow imaging. Methods From August 2021 to August 2022, 30 patients with PPR were enrolled from the Department of Dermatology, the First Affiliated Hospital of Baotou Medical College in the Inner Mongolia Autonomous Region, and 30 healthy volunteers served as controls. The 22-MHz high-frequency ultrasound combined with color Doppler blood flow imaging was performed to measure the skin thickness, echo and blood flow parameters at the cheek, and the ultrasound results were compared between the two groups. Comparisons between groups were conducted by using t test or chi-square test. The diagnostic value was analyzed using the area under the curve （AUC） in the receiver operating characteristic （ROC） curve. Results In the case group, there were 12 males and 18 females, and their ages ranged from 22 to 65 years （42.3 ± 12.8 years）; in the control group, there were 10 males and 20 females, and their ages ranged from 24 to 62 years （41.0 ± 8.4 years）. The epidermal and dermal thicknesses at the cheek were significantly higher in the case group （132.64 ± 12.29 μm, 1 812.29 ± 85.52 μm, respectively） than in the control group （104.34 ± 14.45 μm, 1 671.77 ± 146.55 μm, respectively, both P < 0.05）. High-frequency ultrasound images showed that the case group was mainly characterized by irregular hypoechoic areas in the cheek dermis （80%）, while banded moderately echoic areas were common in the cheek dermis in the control group （90%）; subepidermal low-echogenic bands and dermal irregular hypoechoic areas were more likely to appear in the case group than in the control group （93.33% vs. 43.33%, 80% vs. 10%, respectively, both P < 0.001）. Compared with the control group, the case group showed a significantly increased proportion of patients with abundant blood flow signals （93.3% vs. 10%, P < 0.05）, and significantly increased blood vessel diameters （1.60 ± 0.42 mm vs. 0.95 ± 0.32 mm, P < 0.05）; there was no significant difference in peak systolic blood flow velocity and vascular resistance index between the two groups （both P > 0.05）. The AUC of high-frequency ultrasound combined with color Doppler flow imaging quantitative parameters （including epidermal thicknesses, dermal thicknesses, and blood vessel diameters） was 0.989 （95% CI: 0.970 - 1.000） for the diagnosis of PPR, and the sensitivity and specificity were both 96.7%, which were higher than those of single parameter-based diagnostic model. Conclusion High-frequency ultrasound combined with color Doppler flow imaging can help improve the accuracy of the diagnosis of PPR, by accurately and non-invasively measuring skin thickness and blood flow parameters.

Key words: Rosacea, Diagnosis, Papulopustular rosacea, High-frequency ultrasound, Color Doppler flow imaging