Epidemiological survey and clinical investigation of pediatric IgA nephropathy

Since school urinalysis screening was introduced in 1974, the number of cases requiring initiation of dialysis due to glomerulonephritis has been steadily decreasing and school urinalysis screening has been praised for contributing to the early detection and treatment of glomerulonephritis. However, the lack of nationwide epidemiological surveys is also a problem.

We conducted an epidemiological survey focusing on the frequency of occurrence of pediatric IgA nephropathy in Nishinomiya City. Subjects comprised 374,846 children who underwent school urinalysis screening from 2003 to 2012. Renal biopsy findings and clinical findings of these pediatric IgA nephropathy cases were retrospectively investigated.

There were 37 (mean 3.7/year) newly diagnosed cases of pediatric IgA nephropathy in Nishinomiya City. The IgA nephropathy onset rate per 100,000 children who underwent school urinalysis screening was 9.9 cases/year. Compared to the histologic low grade group, the histologic high grade group had significantly higher urinary P/C ratio (P < 0.001). In the histologic high grade group, the number of cases of proteinuria remission 3 years after starting treatment was significantly higher in the group treated with steroids (P = 0.045).

Our study found that 9.9 cases of pediatric IgA nephropathy were diagnosed per 100,000 in the pediatric population, which is equivalent to or slightly more than past reports. IgA nephropathy, which poses a high histologic risk, presents with heavy proteinuria; but the proteinuria remission rate following steroid therapy is high 3 years after treatment, which suggests that administration of steroids results in an improved clinical outcome.