New epidemiological characteristics of childhood IgA vasculitis in the post-COVID-19 era: a single-center retrospective cohort study

To compare hospitalization characteristics, clinical phenotypes, risk factors for IgA vasculitis nephritis (IgAVN), and prognostic outcomes in children with IgA vasculitis (IgAV) before and after the COVID-19, thereby elucidating the impact of the pandemic on the disease spectrum of IgAV to provide evidence for optimized disease management and precision medicine in the Post-COVID-19 era. A single-center retrospective cohort study was conducted involving children hospitalized with IgAV during two periods: Pre-COVID-19 (2017–2019) and the Post-COVID-19 endemic phase (2023–2025). We systematically compared general demographics, clinical phenotypes, and etiological profiles between the two cohorts. IgAV hospitalization proportions were calculated, and time-series models predicted crude hospitalization rates to assess burden trends. Furthermore, a 6-month follow-up was performed for newly-diagnosed non-nephritic patients to evaluate relapse rate and progression to IgAVN. Finally, multivariate logistic regression identified independent IgAVN risk factors. Compared to the Pre-COVID-19 period, patients in the Post-COVID-19 era exhibited significant alterations in humoral immunity and complement profiles, alongside increased rates of Mycoplasma pneumoniae infection. The disease burden intensified markedly: hospitalization duration, costs, and the proportion of IgAV admissions (including both newly-diagnosed and relapsed cases) surged, with the observed crude hospitalization rate significantly exceeding model predictions. Among newly-diagnosed cases, the proportion of the renal subtype increased significantly, while the cutaneous-only form decreased. Follow-up data revealed no significant difference in relapse rates between cohorts; However, the progression rate to nephritis was significantly elevated in the Post-COVID-19 group. Duration of rash emerged as the sole consistent independent predictor of IgAVN across both periods. In the post-COVID-19 era, childhood IgAV presents with new clinical characteristics, marked by an increased overall disease burden and a shift towards more severe clinical phenotypes. These changes may be associated with rising Mycoplasma pneumoniae infection and dysregulation of the complement-coagulation system.Notably, newly-diagnosed non-nephritic patients face a significantly higher risk of renal involvement, underscoring the need for enhanced early clinical monitoring and long-term follow-up. While the spectrum of risk factors for IgAVN has evolved, rash duration remains a critical predictor requiring close attention.