Syndromic hidradenitis suppurativa in the European Registry for Hidradenitis Suppurativa (ERHS-Be)

Introduction: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease, characterized by painful and recurrent lesions in apocrine gland-bearing skin areas. It is a heterogeneous disease, often associated with other pathologies. Rarely, specific associations form syndromes. The Belgian European Registry for Hidradenitis Suppurativa (ERHS-Be) is a registry that allows identification of syndromic cases of HS in a large HS cohort. Uncovering those complex cases leads to better management, targeting the underlying etiopathogenic factors. Material and methods: The ERHS-Be registry is based on questionnaires, which include a wide array of features and a physical examination that allow recognition of syndromes. It also enables identification of phenotypes and automatic calculation of severity scores. Results: The ERHS-Be currently includes 606 patients with HS. A few syndromic cases exist within this cohort. We report 2 PASH syndromes, 1 PASS syndrome, 1 PAPASH, 3 follicular occlusion triads, 1 follicular occlusion tetrad and 1 case of HS associated with Down syndrome. We also describe a few cases with noteworthy associations: 3 cases of HS with pyoderma gangrenosum, 1 case of HS with familial mediterranean fever, 1 case of HS with spondyloarthritis and psoriasis and 1 case of HS with spondyloarthritis, psoriasis and Crohn’s disease. Syndromic HS prevalence in our HS cohort is 2.5%. Most of these cases have a Hurley 1 stage and a mild IHS4 severity score. The main HS phenotype is Dudink et al.’s regular phenotype. Conclusion: The ERHS-Be allows systematic and large data collection. Analysis of the content enables identification of rare syndromic cases. Due to their complex clinical presentation, treatment is challenging and should be individualized, targeting the underlying etiopathogenic factors.