Patients with rheumatic diseases share similar patterns of healthcare resource utilization.

: Healthcare service needs have changed with the use of effective treatment strategies. Using data from the modern era, we aimed to explore and compare health service-related direct costs in juvenile idiopathic arthritis (JIA), psoriatic arthritis (PsA), rheumatoid arthritis (RA), and axial spondyloarthritis (AxSpA). : We linked a longitudinal, population-based clinical data set from Finland's largest non-university hospital's rheumatology clinic with an administrative database on health service-related direct costs in 2014. We compared all-cause costs and costs of comorbidities between adult patients with JIA, PsA, RA, and AxSpA (including ankylosing spondylitis). We also characterized patients with high healthcare resource utilization. : Cost distributions were similar between rheumatic diseases (p = 0.88). In adulthood, patients with JIA displayed a similar economic burden to much older patients with other inflammatory rheumatic diseases. A minority were high utilizers: among 119 patients with JIA, 15% utilized as much as the remaining 85%. For PsA (213 patients), RA (1086), and AxSpA (277), the high-utilization proportion was 10%. Both low and high utilizers showed rather low disease activity, but in high utilizers, the patient-reported outcomes were slightly worse, with the most distinct differences in pain levels. Of health service-related direct costs, index rheumatic diseases comprised only one-third (43.6% in JIA) and the majority were comorbidity costs. : Patients with JIA, PsA, RA, and AxSpA share similar patterns of healthcare resource utilization, with substantial comorbidity costs and a minority being high utilizers. Innovations in meeting these patients' needs are warranted.