Supplementary Material for: Adolescent-Onset Hidradenitis Suppurativa: Prevalence, Risk Factors and Disease Features

<b><i>Background/Aims:</i></b> Hidradenitis suppurativa (HS) is a chronic inflammatory and destructive skin disorder. Early diagnosis and treatment are critical to stop its progression. Data concerning adolescent-onset HS are scarce. The aims of this study are to describe the prevalence of adolescent-onset HS and to explore potential risk factors and the disease features of these patients. <b><i>Patients and Methods:</i></b> A cross-sectional study including 134 patients was performed. <b><i>Results:</i></b> Adolescent-onset HS occurred in 51.5% (69/134) of patients. Adolescent-onset HS was associated with female sex, positive family history, presence of pilonidal sinus, acne conglobata, longer disease duration and a worse perception of disease severity. <b><i>Conclusion:</i></b> Adolescent-onset HS might be more frequent than previously reported. Female sex, positive family history and the presence of elements of the follicular occlusion tetrad identify individuals with a higher risk of early onset. These patients experience a longer disease duration and perceive their disease as severer.