Patterns of kidney involvement after corticosteroid treatment for extrarenal symptoms in pediatric IgA vasculitis (Henoch–Schönlein Purpura): Phenotypes and outcomes

Background Corticosteroids are frequently used for extrarenal manifestations of Immunoglobulin A Vasculitis (IgAV), but their impact on the development and patterns of kidney involvement remains unclear. This study aimed to evaluate whether early steroid administration for extrarenal symptoms influences the incidence, timing, and phenotypic expression of renal involvement. Methods We retrospectively analyzed pediatric IgAV patients at a single tertiary center between 2019 and 2025. Patients were stratified according to whether systemic corticosteroids were administered within four weeks of disease onset for extrarenal symptoms. Outcomes included the incidence, timing, and phenotypic severity of kidney involvement, as well as rates of urinary normalization. Results Among 211 patients, kidney involvement occurred in 21.7% of the steroid-treated group and 11.8% of the non-steroid group ( p  = 0.054). The steroid group exhibited significantly higher baseline disease severity, including gastrointestinal (73.9%) and joint (67.4%) symptoms, along with elevated inflammatory markers at presentation. There was no significant difference in the median time to kidney involvement between groups (1.03 vs. 0.72 months). However, steroid-treated patients were significantly more likely to present with a combined pattern of microscopic hematuria and mild proteinuria (50.0% vs. 21.4%, p  = 0.021). Notably, in the moderate proteinuria subgroup, none of the steroid-treated patients achieved full urinary normalization, compared to 75% of the non-steroid group. Conclusions Early corticosteroid treatment for extrarenal IgAV symptoms does not prevent, delay, or mask subsequent kidney involvement. While it shifts the phenotypic expression toward milder hematuria–proteinuria patterns, it may not improve long-term urinary resolution in cases with more severe proteinuria.