Early signs of kidney damage in children with juvenile idiopathic arthritis: a narrative literature review

Background. Juvenile idiopathic arthritis (JIA) comprises a heterogeneous group of chronic inflammatory arthritides of childhood in which immune-mediated and immune-inflammatory mechanisms play a central pathogenic role. In addition to musculoskeletal involvement, persistent systemic inflammation, endothelial dysfunction, and exposure to potentially nephrotoxic medications may contribute to subclinical renal involvement. Historically, kidney complications in JIA were recognized mainly at advanced stages, including secondary AA amyloidosis and clinically overt drug-related nephrotoxicity. More recent clinical studies indicate that subtle urinary, functional, and vascular abnormalities may be detectable early in the disease course, before the development of clinically apparent renal dysfunction. The purpose was to synthesize current evidence on early clinical, laboratory, hemodynamic, and molecular markers of renal involvement in children with JIA, to characterize their potential role in early detection and treatment monitoring, and to formulate a risk-oriented approach to nephrological surveillance. Materials and methods. A structured narrative literature review was conducted using publications retrieved from PubMed. English-language articles published from 2021 through 2026 were screened. Eligible publications included original clinical studies, retrospective and prospective cohort studies, and meta-analyses reporting quantitative or qualitative data on renal status in children with confirmed JIA, including proteinuria or albuminuria, hematuria, cystatin C-based estimated glomerular filtration rate (eGFR), tubular injury biomarkers, and ambulatory blood pressure monitoring (ABPM). Studies published before 2021, duplicate records, and publications unrelated to renal outcomes in JIA were excluded. The pediatric age range was 1.5–18 years. Results. The reviewed evidence was consistent with a pathophysiological spectrum of renal involvement in JIA, ranging from endothelial activation and low-grade urinary abnormalities to changes in glomerular filtration and vascular regulation. Treatment-naive children with newly diagnosed JIA showed higher 24-hour urinary protein excretion and urinary red blood cell counts than healthy controls. Cystatin C-based eGFR identified reduced filtration estimates in a proportion of children with active JIA, while ABPM demonstrated abnormal circadian blood pressure profiles, including a non-dipping pattern. Conclusions. Subclinical renal involvement in JIA may be underrecognized and can precede overt nephropathy. Integration of quantitative urinary protein or albumin assessment, cystatin C-based eGFR, and ABPM into risk-based clinical surveillance may facilitate earlier recognition of renal abnormalities and more timely adjustment of therapy.

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