Prevalence of Inflammatory Bowel Disease and Celiac Disease in Patients with IgA Nephropathy over Time

<b><i>Introduction:</i></b> IgA nephropathy (IgAN) has been connected with increased intestinal permeability and subclinical intestinal mucosal inflammation as well as with inflammatory bowel disease (IBD) and celiac disease – nevertheless, the results are controversial. The prevalence of bowel diseases has increased over time in Western populations. Whether similar trend is seen among IgAN patients remains obscure. Our aim was to study the prevalence of IBD and celiac disease in IgAN patients over time. <b><i>Methods:</i></b> The study cohort consisted of altogether 629 patients with newly diagnosed IgAN during years 1976–2012. Data on diagnosis of IBD and celiac disease were retrospectively collected from medical records. Further, to detect unrecognized celiac disease, IgA-class tissue transglutaminase antibodies (tTGA) were measured from serum samples taken at the time of kidney biopsy during years 1980–2012 (defined as screen-detected celiac disease autoimmunity). <b><i>Results:</i></b> The prevalence of IBD among IgAN patients increased over time from 0 to 4.4%, while the prevalence of clinically diagnosed celiac disease decreased from 2.6 to 0.6%. Moreover, the number of screen-detected tTGA-positive cases decreased from the 1980s to the 21st century (2.8–0.7%). <b><i>Conclusion:</i></b> The prevalence of IBD increased over time in IgAN patients, which exceeds the prevalence of 0.6% in Finnish general population. In parallel, the prevalence of celiac disease and screen-detected celiac disease autoimmunity decreased over time. The coexistence of IBD and IgAN is not negligible. Whether this finding is caused by the increase in the prevalence of IBD in the population or shared pathophysiology between IgAN and IBD remains a matter of further studies.