# Aetiology of acute/subacute nephritic syndrome: results from kidney biopsy registries in Japan and Europe

## TL;DR

This study compares the causes of acute/subacute nephritic syndrome in Japan and Europe, finding similar and different patterns across regions.

## Contribution

The study provides a comparative analysis of kidney biopsy data from multiple regions to identify the most common causes of acute/subacute nephritic syndrome.

## Key findings

- ANCA-associated vasculitis is the most common cause of acute/subacute nephritic syndrome in both Japan and Europe.
- European patients had a higher estimated GFR and were younger on average compared to Japanese patients.
- IgA nephropathy/vasculitis and acute interstitial nephritis are also significant causes in both regions.

## Abstract

The combination of hematuria, proteinuria and a reduced glomerular filtration rate (GFR) in patients with no previous diagnosis of chronic kidney disease is widely considered a strong indication for kidney biopsy. This study aimed to compare the frequencies of diseases leading to this symptom constellation, and to explore differences related to age and sex using data from kidney biopsy registries in Europe and Japan.

Data were retrieved from national or regional kidney biopsy registries in Japan, Sweden, Norway, Scotland, Austria, Croatia and Turkey from January 1, 2007, to December 31, 2019. Patients were included if the indication for kidney biopsy was acute/subacute nephritic syndrome, which was defined as a combination of hematuria, proteinuria and reduced GFR in a patient without a prior diagnosis of chronic kidney disease. Demographic, clinical and laboratory data were collected at the time of kidney biopsy.

A total of 1023 patients from Europe and 2477 from Japan were included in the study. The primary cause of acute/subacute nephritic syndrome in both regions was ANCA-associated vasculitis, followed by IgA nephropathy/vasculitis and acute interstitial nephritis. The estimated GFR was higher in Europe than in Japan, at 24 and 20 ml/min/1,73 m2, respectively. The median age was 10 years younger in European patients than in Japanese patients.

The most common underlying causes of acute/subacute nephritic syndrome are ANCA-associated vasculitis, IgA nephropathy/vasculitis and acute interstitial nephritis. This study highlights both similarities and differences in the spectrum of underlying diagnoses and clinical presentations across ages, sexes, and geographical regions in patients presenting with acute/subacute nephritic syndrome.

The online version contains supplementary material available at 10.1186/s12882-025-04582-6.