Clinical impact of endocapillary proliferation according to the Oxford classification among adults with Henoch-Schönlein purpura nephritis: a multicenter retrospective cohort study

BACKGROUND: Henoch-Schönlein purpura nephritis (HSPN) is a form of small vessel vasculitis associated with purpura and IgA deposition in the glomeruli. The International Study of Kidney Disease in Children (ISKDC) classification predicts renal prognosis in children with HSPN, but not in adults. Additionally, it is not well known whether the Oxford classification 2016 and/or the Japanese Histologic classification (JHC) are associated with renal outcome. Herein, we investigated the relationship between pathological characteristics and renal outcome among adult patients with HSPN. METHODS: A multicenter retrospective cohort study was conducted in adult patients with HSPN who underwent renal biopsy between 2004 and 2014. Two nephrologists classified each patient according to the Oxford classification 2016, JHC, and the ISKDC classification. Renal outcome was defined by a 30% decline in the eGFR and/or end-stage kidney disease. RESULTS: We enrolled 74 adult patients with HSPN (mean age, 47.8 ± 17.4 years; mean eGFR, 76.4 ± 25.8 ml/min/1.73 m(2); median proteinuria, 1.40 [IQR: 0.70–2.38] g/day). During a mean follow-up period of 68.0 ± 33.0 months, fourteen patients (18.9%) reached the renal outcome, and all 14 had received immunosuppressive therapy. The log-rank test revealed that event-free renal survival was significantly shorter in patients with endocapillary proliferation (E1) according to the Oxford classification than in those with E0 (p = 0.0072). However, the JHC, ISKDC classification and other Oxford lesions could not demonstrate a significant difference in event-free renal survival. In a multivariate Cox model adjusted for clinical and pathological factors, age (HR, 1.57; 95% CI, 1.12–2.21) and E lesion (HR, 6.71; 95% CI, 1.06–42.7) were independent risk factors for renal outcome. CONCLUSIONS: Endocapillary proliferation is significantly associated with renal outcome in adult patients with HSPN, including those receiving immunosuppressive therapy. Other Oxford classification lesions, JHC, and ISKDC classification were not associated with renal outcome. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12882-018-1009-z) contains supplementary material, which is available to authorized users.