Pediatric IgA Nephropathy in Europe.

Background: In Europe IgA nephropathy (IgAN) is detected in 20% of children with glomerular diseases diagnosed by renal biopsy. The outcome during childhood is generally good, but progression in the long-term follow-up may occur in about 20% of children after 20 years.

Summary: In Europe, urine screening programs are not active, and there is variability in the policy to perform renal biopsies in oligo-symptomatic children. Hence, a suitable observational approach to pediatric IgAN is offered by the VALIGA study which included 174 children aged < 18 years from 13 European countries followed over a median of 4.4 (2.5-7.5) years. Renal pathology lesions were centrally scored according to the Oxford Classification of IgAN (mesangial hypercellularity, M; endocapillary hypercellularity, E; segmental glomerulosclerosis, S; tubular atrophy/interstitial fibrosis, T; crescents, C [MEST-C]). Children had renal biopsy mostly with normal estimated glomerular filtration rate (eGFR) and moderate proteinuria of a median of 0.84 g/day/1.73 m² (< 0.30 g/day/1.73 m² in 30% of the cases). Children showed M1 in 21.8%, E1 in 13.8%, S1 in 42.5%, T1-2 in 6.3%, and C1 in 14.9%. The survival at the combined endpoint of 50% eGFR decrease or end-stage renal disease at 15 years was 94%. The slow progression rate and the limited number of cases progressing to the combined endpoint (6.4%) did not allow the detection of a predictive value of the MEST-C score. Moreover, the predictive value of clinical and pathological features was likely blunted by the use of corticosteroid/immunosuppressive treatment (CS/IS) in 50% of the cases. The survival tree analysis also proved that children < 16 years old with IgAN without mesangial hypercellularity (M0) and well preserved eGFR (> 90 mL/min/1.73 m²) had a high probability of proteinuria remission during follow-up. Moreover, in this subgroup of children, the benefits of CS/IS therapy reached statistical significance. In Europe, the use of CS/IS treatment in IgAN is still a debated issue, but most children tend to be treated more commonly than adults with CS/IS. A recent uncontrolled study reports a favorable outcome in European children with IgAN and very active acute forms of IgAN with improvement in eGFR and reduction in proteinuria.

Key Messages: In Europe, children with IgAN have a favorable prognosis in the short term, and this may be due also to the frequently adopted CS/IS therapy, particularly with acute and active pathological features. The risk of progression over decades of follow-up remains an unsolved problem which needs to be addressed by controlling subtle chronic pathogenetic factors which work in children as well as in adult cases of IgAN.