# Diagnosis and treatment in adult patients with C3 glomerulopathy in Japan: a real-world survey

## TL;DR

This study examines the real-world diagnosis and treatment of C3 glomerulopathy in Japan, highlighting delays in diagnosis and the lack of approved therapies.

## Contribution

The study provides insights into the diagnostic challenges and treatment patterns of C3G in Japan through a real-world survey of nephrologists.

## Key findings

- Median time from initial examination to C3G diagnosis was 8.4 weeks, with some patients waiting over 8 months.
- Common treatments included angiotensin receptor blockers, corticosteroids, and sodium-glucose cotransporter-2 inhibitors.
- Physicians reported 19% of patients had a gradually deteriorating disease condition.

## Abstract

C3 glomerulopathy (C3G) is an ultra-rare, complex, under-recognized kidney disease with a challenging diagnosis and no approved treatment. Nephrologists were surveyed to understand the treatment and management of C3G. This study presents the diagnostic challenges and treatment patterns of Japanese patients with C3G.

Data from the Adelphi C3G Disease Specific Programme™, a multinational survey of nephrologists treating patients with C3G in 8 countries including Japan, were retrospectively analyzed. Nephrologists completed patient-record forms on patient demographics, diagnosis, clinical characteristics, and treatment approaches.

Sixteen nephrologists from Japan responded to the survey for 36 patients with C3G. Mean age at diagnosis and at the time of the survey was 45.4 and 48.6 years, respectively. Common symptoms at diagnosis were proteinuria (100%) and hematuria (83%); 79% of patients had proteinuria of  ≥1 g/day, and 3% had an estimated glomerular filtration rate of <30 mL/min/1.73 m2. Median time from initial examination by general practitioner to definitive diagnosis was 8.4 weeks; ~20% and 10% of patients had to wait for >4 and >8 months, respectively, to get a confirmed C3G diagnosis; and 69% of patients had an additional biopsy. Angiotensin receptor blockers (68%), corticosteroids (64%), and sodium-glucose cotransporter-2 inhibitors (25%) were the main treatments utilized. Physicians perceived 19% of patients to have a gradually deteriorating disease condition.

This survey analysis explored the current status in diagnosis and management of patients with C3G in Japan. The lack of specific treatments emphasizes the need for novel targeted therapies addressing the root cause of C3G.

The online version contains supplementary material available at 10.1007/s10157-025-02779-5.