BackgroundIgG4-related disease (IgG4-RD) is an immune-mediated condition that can affect nearly any organ or anatomic site. We sought to describe the epidemiology of IgG4-RD in the USA.MethodsWe used Optum’s deidentified Clinformatics Data Mart Database from 1 January 2009 to 31 December 2021 to identify IgG4-RD cases using a validated algorithm. We estimated the incidence rate and prevalence between 2015 and 2019 (when rates stabilised), standardised to the US population by age and sex. We compared mortality rates among patients with IgG4-RD to the non-IgG4-RD population matched in a 1:10 ratio on age, sex, race/ethnicity and encounter date. We used Cox proportional hazards models to estimate HRs and 95% CIs.ResultsWe identified 524 IgG4-RD cases. The mean age was 56.5 years with 57.6% female and 66% White. The incidence of IgG4-RD increased during the study period from 0.78 to 1.39 per 100 000 person-years in 2015 and 2019, respectively. The point prevalence on 1 Janury 2019 was 5.3/100 000 persons. During follow-up, there were 39 and 164 deaths among 515 IgG4-RD cases and 5160 comparators, resulting in a mortality rate of 3.42 and 1.46/100 person-years, respectively, and adjusted HR of 2.51 (95% CI 1.76 to 3.56).ConclusionsThe incidence of IgG4-RD is similar to that of systemic rheumatic diseases such as ANCA-associated vasculitis and systemic sclerosis but may be increasing as familiarity with this diagnosis grows. Clinicians should be aware of this condition, especially given the excess risk of death. Identification of effective therapies is an important research agenda.

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