OP0184 THE INCIDENCE AND CLINICAL FEATURES OF IgG4 RELATED DISEASE

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Background: Data on the incidence of IgG4-related diseases (IgG4 RD) are scarce. A recent USA study reported incidence rates ranging from 0.78 to 1.39 per 100 000 person-years for the period 2015-2019 [1]. Objectives: The aim of our study was to retrospectively estimate the incidence rate of IgG4RD in the adult population of a well-defined country region. Methods: The study covered a 13-year period, from January 2012 to November 2024. Chart review of adults diagnosed with IgG4RD was performed at the departments of rheumatology, nephrology, angiology, gastroenterology, abdominal surgery, ENT surgery, ophthalmology of an integrated secondary/tertiary university teaching hospital. The hospital is the only referral centre for an average adult population of 541,600 residents (homogeneous European population). Cases of IgG4RD followed at department of rheumatology were collected prospectively, while in other departments potential cases were retrieved by searching computer medical database for the key word "IgG4". In addition, the Institute of Pathology provided a list of patients with an IgG4RD compatible histological pattern on biopsy for the same period. The year-specific incidence rates and an average incidence rate for the 13-year period of IgG4RD were calculated. Clinical features of patients were analysed. Results: From January 2012 to November 2024, 58 cases of IgG4RD were diagnosed. 35 out of 58 patients were residents of a region under investigation. The estimated average annual incidence rate of IgG4RD in the 13-year period was 5.0 per 1 000 000 adults (95% confidence interval (CI) 3.5; 6.9), and a year-specific incidence rate fluctuated from 1.8 (95%CI 0.05; 10.0) to 9.3 (95%CI 2.9; 21.2) cases per 1 000 000 adults. Table 1 shows characteristics of IgG4RD cohort. The median age at diagnosis was 64 (53; 68) years, 74.3% were males (male to female ratio of 2.9) and 58.1% were ever smokers. Median symptom duration time before diagnosis was 6 (3; 14) months. Based on the IgG4RD phenotypes, 17%, 43%, 14% and 26%, cases were stratified into pancreato-biliary disease, retroperitoneal fibrosis and/or aortitis, head and neck limited disease and Mikulicz syndrome with systemic involvement, respectively. The average number of organs/regions affected at diagnosis was two (ranging from one to five organs). Conclusion: The average annual incidence rate of IgG4RD was estimated at 5.0 per 1 000 000 adults, and retroperitoneal fibrosis and/or aortitis phenotype predominated in our population. REFERENCES: [1] Wallace ZS, et al. DOI: 10.1136/ard-2023-223950. Acknowledgements: NIL . Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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