BACKGROUND: Systemic steroids are recommended for patients with IgA nephropathy (IgAN) and proteinuria. However, there are concerns about their safety due to an excess of serious adverse events (SAEs) in previous randomised trials. This study evaluates the incidence of SAEs in IgAN patients receiving different treatment regimens in clinical practice. METHODS: Multicentre, retrospective, observational cohort study of 1209 patients (M/F: 864/345, mean age: 41.73 ± 14.92 years) with biopsy-proven IgAN treated with renin angiotensin system (RAS) inhibitors (RASI) (n = 285), intravenous + oral steroids (n = 633), oral steroids (n = 99), steroids + immunosuppressants (n = 192). RESULTS: A total of 119 (9.8%) adverse events were reported, of which 67 (5.5%) were considered treatment-emergent, and 36 (2.9%) were SAEs (n = 23, 63.8% were infections). One patient died due to sepsis. A significant association was observed between AEs and immunosuppression [8 (2.8%) in RASI, 60 (9.4%) in steroids + immunosuppressants, 14 in oral steroids (14.1%) and 37 pts (19.2%) in steroids + immunosuppressants (p <
0.01)], age and estimated glomerular filtration rate (eGFR), but not with proteinuria and sex. On multivariate analysis, only older age was associated with the occurrence of SAEs. CONCLUSIONS: According to our findings, the incidence of SAEs during therapy with steroids alone or associated with immunosuppressors is lower in everyday clinical practice than in randomised clinical trials.