Supplementary Material for: Ethnic Differences in Hidradenitis Suppurativa: Comorbidities, Lesion Distribution, and Disease Severity in a Taiwanese Population

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory debilitating disorder showing ethnic heterogeneity in its clinical presentation and associated comorbidities. However, data on East Asian populations remain scarce. Methods: We conducted a retrospective analysis of clinical records for patients with HS diagnosed between 2006 and 2022 at two tertiary referral hospitals in Taiwan. Age- and sex- matched reference individuals without HS (3:1 ratio) were randomly selected from dermatology outpatients. Association between comorbidities and HS were analyzed using conditional logistic regression, while logistic regression identified predictors for lesion distribution and disease severity. Results: A total of 512 patients with HS and 1,536 reference individuals were identified. Comorbidities independently associated with HS were obesity, smoking, and diabetes. Men had 4.2 times the odds of developing gluteal lesions but only 0.5 times the odds of axillary or inguinal involvement compared to women. Current smokers had 2.8 times the odds of gluteal involvement but 0.6 times the odds of having axillary lesions. A significant association was observed between obesity and axillary involvement. Advanced disease (Hurley stage II and III) was significantly associated with male sex, smoking, and axillary involvement. Conclusion: Our study highlights distinct lesion distribution in East Asian patients with HS. Male sex and active smoking could predict for gluteal involvement, while female sex and obesity for axillary involvement. Independent risk factors for advanced disease were male sex, smoking, and axillary involvement.