IgA nephropathy in children: before and after the start of COVID-19

Background We describe the clinical course of children with IgA nephropathy (IgAN), diagnosed before and after the emergence of COVID-19. We hypothesized that COVID-19 vaccination and/or infection resulted in more children with IgAN to present clinically. Methods We conducted a retrospective cohort study of children with IgAN diagnosed on kidney biopsy from 2014–2020 (Period 1) and 2021–2022 (Period 2). Baseline characteristics, clinical presentation, investigations and treatments were compared between patients diagnosed in Period 1 and Period 2, as well as between patients with and without chronic changes on kidney biopsy. Continuous variables were compared using the Wilcoxon rank sum test. Categorical variables were compared using χ2 or Fisher exact tests. Results Nineteen children with IgAN were diagnosed by kidney biopsy, with 10 during Period 1 and 9 patients during Period 2 (an average of 1–2 patients/year and 4–5 patients/year in Periods 1 and 2, respectively). The most common indication for kidney biopsy is proteinuria with urine protein/creatinine ratio 1.4 (interquartile range [IQR] 1.2–9.0) vs. 0.8 (IQR 0.6–1.5) g/g ( p = 0.064) at time of kidney biopsy for patients in Period 1 and 2, respectively. Clinical course was similar in both periods. No patient required acute or chronic kidney replacement therapy. Conclusions The rate of diagnosing children with IgAN was higher since the emergence of COVID-19, suggesting that COVID-19 may trigger an immune response responsible for IgAN, similar to other mucosal infections. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information