Clinical manifestations of Henoch–Schönlein purpura nephritis and IgA nephropathy: comparative analysis of data from the Japan Renal Biopsy Registry (J-RBR)

Background: The clinical presentation of Henoch–Schönlein purpura nephritis (HSPN) has not been thoroughly investigated among patients of different ages. We therefore compared the features of HSPN and IgA nephropathy (IgAN) based on data from the Japan Renal Biopsy Registry (J-RBR). Methods: This cross-sectional study analyzed data from patients who were registered in the J-RBR between 2007 and 2012. Clinico-pathological findings at diagnosis were compared among children (aged ≤18 years), adult (aged 19–64 years) and elderly (aged ≥65 years) patients with HSPN (n = 513) and IgAN (n = 5679). Results: The age at diagnosis considerably differed between HSPN and IgAN; HSPN peaked at 1–19 and at 60–69 years, whereas IgAN peaked at 30–39 years. The clinical features were significantly more severe for HSPN than IgAN, especially proteinuria (children, 1.28 vs. 0.57; adult, 1.95 vs. 1.05; elderly patients, 2.71 vs. 1.64 g/day), and low albumin levels (children, 3.72 vs. 4.13; adults, 3.62 vs. 3.99; elderly patients, 3.07 vs. 3.57 g/dL). The rate (%) of histologically classified endocapillary proliferative or crescentic glomerulonephritis was higher in patients with HSPN than with IgAN. Multiple regression analysis revealed that low albumin level and high BP were independent factors associated with decreased estimated glomerular filtration rates in adult and elderly patients with HSPN. Conclusions: Age at HSPN diagnosis was bimodally distributed, and the clinical features of HSPN were more severe than those of IgAN across all age groups.