Incidence and prevalence of hidradenitis suppurativa across spondyloarthritis-related diseases

ImportanceHidradenitis suppurativa (HS) has been associated with spondyloarthritis (SpA) and inflammatory bowel disease (IBD) and proposed as a potential manifestation of these conditions. However, the relative rarity of HS, combined with the diverse methodologies used in previous studies, leaves several uncertainties surrounding its epidemiology within this disease spectrum. ObjectiveTo describe the prevalence and incidence of HS across pathologically related diseases within the spondyloarthritis (SpA) family, namely psoriasis, psoriatic arthritis (PsA), axial spondyloarthritis (axSpA), uveitis, Crohns disease, and ulcerative colitis. DesignCohort study conducted using data between January 2005 and January 2025. SettingThe study used data from electronic health records of over 135 million individuals across more than 100 healthcare organizations in North America. ParticipantsSix disease populations ranging from 46,928 to 191,605 individuals. ExposuresPopulations of psoriasis, PsA, axial spondyloarthritis, uveitis, Crohns disease, and ulcerative colitis. Main outcomes and measuresPrevalence and incidence per 100,000 patient-years of HS. ResultsThe prevalence of HS was 0.4% in psoriasis and PsA, higher than axSpA (0.2%), Crohns disease (0.3%) or ulcerative colitis (0.2%). HS incidence was higher in psoriasis (124/100,000 patient-years) and PsA (119/100,000 patient-years) than other SpA-related disease (range 69 to 88/100,000 patient-years), with the exception of Crohns disease (177//100,000 patient-years). Conclusions and RelevanceThis study highlights a significant epidemiological association between HS and SpA-related diseases, particularly psoriatic disease and Crohns disease. Clinicians providing care to these patient groups should consider enquiring about HS symptoms, although overall incidence rates are low. Further research is needed into the shared pathophysiology of HS and psoriatic disease. Key pointsO_ST_ABSQuestionC_ST_ABSWhat is the prevalence and incidence of hidradenitis suppurativa (HS) in conditions with shared immunopathology such as psoriatic disease, axial spondyloarthritis, uveitis, and inflammatory bowel disease? FindingsThis cohort study found high prevalence and incidence of HS among individuals with psoriatic disease and confirmed previously reported high incidence in Crohns disease. Incidence rates of HS in other diseases of the spondyloarthritis family, such as axial spondyloarthritis, were lower. MeaningClinicians providing care for people with psoriatic disease should consider enquiring about HS symptoms, although overall incidence rates are low.