Background: Pediatric idiopathic nephrotic syndrome (INS) is classified primarily by corticosteroid response, delaying identification of steroid-resistant disease and exposing children to unnecessary treatment toxicity. Novel biomarkers could enable earlier biological stratification and treatment guidance. Objectives: The study aimed to map available evidence on candidate biomarkers in pediatric INS published since 2020, with emphasis on anti-nephrin autoantibodies and their potential for clinical translation. Data Sources: PubMed/MEDLINE and Web of Science Core Collection (January 2020–October 2025), with a supplementary verification search in Scopus and Embase and manual reference screening. Eligibility Criteria: Original studies reporting circulating, urinary, or tissue-based biomarkers in children aged 0–18 years with idiopathic NS, with outcomes related to diagnosis, treatment response, relapse prediction, or monitoring. Studies in adults only, secondary NS, or animal models were excluded. Results: After screening, 34 studies met the eligibility criteria and were included, grouped into five categories: autoantibodies, urinary markers, immune cell signatures, cytokines/chemokines, and exploratory markers (metabolomics, extracellular vesicles, lipid profiles, microRNAs). Anti-nephrin IgG emerged as the most mechanistically informative marker, with seroprevalence declining across phenotypes (SSNS 68%, SDNS 28%, non-genetic SRNS 14%, genetic SRNS 2%) and positivity predicting response to intensified immunosuppression. Of the candidates reviewed, urinary NGAL and peripheral B-cell subset monitoring are the most readily implementable with existing laboratory infrastructure. Conclusions: Pediatric INS encompasses a spectrum of immune-mediated podocytopathies that may soon be distinguishable by emerging biomarker profiles. Anti-nephrin autoantibodies provide the strongest mechanistic evidence for an autoimmune podocytopathy.

Background/Objectives: Retinal artery occlusion (RAO) represents an ischemic event of the anterior circulation, driven by impaired blood flow through the ophthalmic branches of the internal carotid artery. Atrial fibrillation (AF) is an increasingly recognized cardioembolic source in patients with RAO, yet its prevalence remains poorly characterized. We conducted a systematic review and meta-analysis to estimate the pooled prevalence of AF in RAO patients and to summarize evidence on its incidence and association with this condition. Methods: Four databases were searched through April 2025, updated on 18 August 2026. Studies reporting AF prevalence, incidence, or association in adults with RAO were included. Pooled prevalence was estimated using the Freeman–Tukey double arcsine transformation with a random-effects model. Subgroup analyses, meta-regression, and sensitivity analyses were performed to explore heterogeneity. Results: Sixty-two studies were included in the qualitative synthesis, of which 58 reported AF prevalence data. Among the 36 studies comprising 139,222 patients, the pooled AF prevalence was 11.53% (95% CI: 9.41–13.82; I² = 99.2%; prediction interval: 2.00–26.9%). AF prevalence was significantly higher in patients aged ≥70 years (15.86%) and in central RAO cohorts (16.54%). Incident AF following RAO ranged from 10.5% to 41%, increasing progressively with monitoring intensity. The pooled odds ratio for the AF–RAO association was 1.56 (95% CI: 1.06–2.29). Conclusions: AF affects approximately one in nine patients with RAO, though with substantial uncertainty across populations (prediction interval 2.00–26.9%); the extent to which this exceeds the general-population estimates independent of age, cardiovascular risk profile, and geographic factors remains uncertain. These findings support cardiac rhythm surveillance following RAO diagnosis in selected patients, although its effect on clinical outcomes remains to be established prospectively.