Assessing Disease Progression in Hurley I Hidradenitis Suppurativa Patients: A Nested Case-Control Study

INTRODUCTION: Hidradenitis suppurativa (HS) is a chronic, progressive, inflammatory skin disease that leads to structural skin alterations, usually assessed using Hurley stages. In Hurley stage I, the earliest phase, structural changes have not yet occurred. However, disease progression varies among patients; some remain indefinitely in this stage, while others advance to more severe forms. The incidence and factors driving progression remain unclear. The aims of this study were to determine the incidence of Hurley II and III cases in a cohort of Hurley I patients and to explore potential factors and interventions associated with structural progression. METHODS: A retrospective cohort study was conducted in Hurley I patients to estimate the cumulative incidence and incidence density of Hurley II-III cases during follow-up. Consecutively, within the cohort of Hurley I patients, a nested case-control study was performed to identify factors associated with structural progression. Patients underwent clinical and ultrasound evaluations. Univariate and multivariate analyses were performed. RESULTS: The study included 133 Hurley I patients evaluated consecutively at the HS unit between January 2017 and March 2024. Mean age was 37.54 (12.87) years, with a female-to-male ratio of 84:49. Regarding progression, cumulative incidence was 50 cases (37.6%) (49 to Hurley II; 1 to Hurley III) and incidence density was 23 cases/100 patients-years. After multivariate analysis, the following variables were significantly and independently associated with progression to Hurley stage: higher number of cigarettes/day (p = 0.009), Hurley Ic stage (p = 0.05), and the increase in abscess count from baseline (categorical) (p = 0.0003). A higher number of abscess drainages (p = 0.047) was associated with a lower risk of progression. CONCLUSION: These findings suggest that clinical features, smoking habits, and treatment-related variables may help identify those patients more likely to progress. Further studies with larger and more representative cohorts are needed to validate these associations.