Clinical and histopathological features of a population-based cohort of 95 consecutive patients with immunoglobulin G4-related disease in Stockholm, Sweden, during a five-year period

OBJECTIVE: To describe the epidemiology, organ involvement, histopathological patterns, and clinical management of immunoglobulin G4-related disease (IgG4-RD) in Stockholm County, Sweden. METHOD: Patients with an International Classification of Diseases, 10th revision, Swedish Edition (ICD-10-SE) diagnosis of IgG4-RD recorded between 2019 and 2023 were identified from the Swedish National Patient Register, encompassing all diagnoses recorded in inpatient and specialist outpatient care. Clinical data, laboratory results, histopathology reports, and treatment information were obtained through systematic medical record review. RESULTS: In total, 112 patients with a registered IgG4-RD diagnosis were identified, of which 95 diagnoses were confirmed after medical record review. The cohort was predominantly male (68%), and 60% had disease involvement of two or more organs. Elevated serum IgG4 was present in 71% of patients. The pancreas, hepatobiliary system, and kidneys were the most frequently affected organs, while salivary gland involvement was comparatively uncommon. Among patients who underwent biopsy (76%), a majority showed histopathological features supportive of IgG4-RD, although only a minority fulfilled multiple histopathological criteria. Comorbidities at the time of diagnosis were similar to those observed in the general older population, although an elevated prevalence of nasal polyposis and asthma was observed. Most patients received systemic glucocorticoids, either alone or in combination with rituximab. Overall, the prognosis was favourable, with high remission rates. CONCLUSION: IgG4-RD in Stockholm County shows a pancreatohepatobiliary-renal dominant pattern, with relatively few glandular cases compared to Asian and US cohorts. Histopathological confirmation was supportive in most biopsied patients, although many affected organs were not biopsied.