Supplementary Material for: Whole-Exome Sequencing in 10 Unrelated Patients with Syndromic Hidradenitis Suppurativa: A Preliminary Step for a Genotype-Phenotype Correlation

<b><i>Background:</i></b> The genetics of syndromic hidradenitis suppurativa (HS), an immune-mediated condition associated with systemic comorbidities such as inflammatory bowel diseases and arthritis, has not been completely elucidated. <b><i>Objective:</i></b> To describe clinical features and genetic signature of patients with the main syndromic HS forms, i.e., PASH, PAPASH, and PASH/SAPHO overlapping. <b><i>Methods:</i></b> Whole-exome sequencing (WES) approach was performed in ten patients with syndromic HS. <b><i>Results:</i></b> Three clinical settings have been identified based on presence/absence of gut and joint inflammation. Four PASH patients who had also gut inflammation showed three different variants in <i>NOD2</i> gene, two variants in <i>OTULIN</i>, and a variant in <i>GJB2</i>, respectively. Three PAPASH and three PASH/SAPHO overlapping patients who had also joint inflammation showed two different variants in <i>NCSTN</i>, one in <i>WDR1</i> and <i>PSTPIP1</i>, and two variants in <i>NLRC4</i>, one of whom was present in a patient with a mixed phenotype characterized by gut and joint inflammation. <b><i>Limitations:</i></b> Limited number of patients that can be counterbalanced by the rarity of syndromic HS. <b><i>Conclusion:</i></b> Syndromic HS can be considered as a polygenic autoinflammatory condition; currently WES is a diagnostic tool allowing more accurate genotype-phenotype correlation.