IPNA clinical practice recommendations for the diagnosis and management of children with IgA nephropathy and IgA vasculitis nephritis

Expected and verified benefits from old and new corticosteroid treatments in IgA nephropathy: from trials in adults to new IPNA-KDIGO guidelines

IgA nephropathy in children has a potential progression risk over decades of adult life. For this reason, pediatric nephrologists tend to treat the disease from the onset, aiming at halting the pathogenetic processes, based on expert opinion and general confidence with steroids for the lack of large pediatric controlled studies. Glucocorticosteroids are widely used, although without full comprehension of the fine molecular effects on IgAN, mostly based on trials performed in adults. In this review, a critical analysis of adult data is provided for extrapolating information useful for children, with a parallel evaluation of the results of the TESTING Trial, employing oral methylprednisolone, and of the NEFIgArd Trial, using enteric release budesonide. Patients' characteristics and the scheme of the two studies are surprisingly similar: Nefecon and methylprednisolone showed 40-50% proteinuria reduction from baseline, with a fast effect of methylprednisolone (3-6 months) and a similar effect on renal function decline. Large genome-wide studies, above-risk alleles, also discovered risk loci targetable by multiple drugs particularly those involved in the modulation of the mucosal immunity priming of B-cells toward the production of galactose deficient IgA1 (Gd-IgA1). The new KDIGO 2024 guidelines under public review in recent months will lower the proteinuria threshold for treatment to 0.5 mg/mg and consider the value of Nefecon in reducing the levels of Gd-IgAI1. The choice between old and new corticosteroids in treating children with IgAN is approaching. In the near future, the genetic data, complemented by blood and urine biomarkers, could be included in tools to guide therapeutic choices and monitoring.

Is Childhood IgA Nephropathy Different From Adult IgA Nephropathy? A Narrative Review

Purpose of the review

Immunoglobulin A (IgA) nephropathy (IgAN) is the most common primary glomerular kidney disease. Children and adults are presumed to have the same disease and are treated similarly. However, there are differences between childhood IgAN and adult IgAN that may require unique treatment considerations, even after transition to adult nephrology services. A narrative review was conducted to compare childhood and adult IgAN and to describe the distinct characteristics of childhood IgAN. Reframing childhood IgAN can inform guideline recommendations unique to childhood IgAN, the development of targeted therapies, and clinical trial design.

Sources of information

Medline and Embase were searched for reports on children and adults with IgAN published between January 2013 and December 2023 (updated May 2024). The search was not restricted by age group, outcomes reported, language, or study design. Randomized controlled trials (RCTs), observational studies, review articles, and nephrology conference abstracts were included. A total of 3104 reports were retrieved. Forty-seven reports (37 primary studies and 10 reviews) were included in the review. Two RCTs and 35 observational studies included a total of 45 085 participants (9223 children and 35 862 adults).

Method

Data were extracted for primary IgAN and not for IgA vasculitis-associated nephritis. Findings were described with no statistical comparisons due to variations in interventions and outcome definitions.

Key findings

Gross hematuria was the obvious clinical difference between childhood IgAN and adult (60-88% vs 15-20%). Nephrotic syndrome was more common in children, approaching up to 44%, while <18% of adults had nephrotic syndrome. Children were biopsied sooner (6 vs 15 months) and had more inflammatory kidney lesions (mesangial hypercellularity: 41-82% vs 38-64%; endocapillary hypercellularity: 39-58% vs 17-34%). Chronic kidney lesions were more prevalent in adults (segmental sclerosis: 62-77% vs 8-51%; interstitial fibrosis/tubular atrophy: 34-37% vs 1-18%). The use of immunosuppressive therapy was higher in children (46-84% vs 35-56%). Children were started on immunosuppressive therapy sooner than adults. Adults were more likely to be optimized with renin-angiotensin system inhibitors (87-94% vs 49-75%). Children had better kidney function than adults at diagnosis (estimated glomerular filtration rate of 90-128 vs 50-88 ml/min/1.73 m2), and children also had better kidney survival, with kidney failure of 3.1% vs 13.4% at 5 years. Children had more risk alleles for IgAN and higher levels of mannose-binding lectin than adults.

Limitations

Most studies were retrospective and observational, with limited data on children and disease mechanisms. Data were not pooled for analysis because of important differences in definitions and measurements of baseline characteristics and outcomes. Data from countries with established urine screening programs were different compared to countries without urine screening programs. Some observed differences may be due to practice variation and delayed diagnosis in adults (lead-time bias). Well-designed prospective studies and standardized measures for kidney function assessment and outcomes can reduce heterogeneity and improve results from reviews.

Conclusion

Inherent differences between childhood IgAN and adult IgAN may be due to distinct disease mechanisms. Approaching childhood IgAN as a separate condition could lead to the discovery of targeted therapies and improve management during childhood and after the transition to adult care.