Abstract
<jats:p>Background. IF-negative acute proliferative glomerulonephritis (APIGN) represents a significant diagnostic pitfall, particularly when complement levels are normal and serological markers are inconclusive. Although classical APIGN is characterized by low C3 and granular C3-dominant immune deposits, an increasing number of pediatric cases present with atypical patterns, raising the risk of misclassification as C3 glomerulopathy or IgA nephropathy. Case reports. We report four pediatric APIGN cases exhibiting heterogeneous serological and immunopathological profiles. All children presented with nephritic features, including hematuria, edema, and hypertension. Despite these similarities, three of the four kidney biopsies demonstrated absent or minimal immune deposits, contrasting with the expected “starry-sky” granular C3 pattern. Light microscopy consistently showed mesangial and endocapillary proliferation, with one case demonstrating crescent formation. Complement levels were within normal limits in all patients, as well as ASO titers. All children experienced clinical improvement with supportive therapy alone, further confirming the diagnosis of APIGN despite atypical immunopathological findings. Conclusions. The predominance of IF-negative biopsies in this series highlights the strong influence of biopsy timing and disease phase on immune-complex detectability in APIGN. Such atypical presentations pose a diagnostic risk, particularly for misclassification as C3 glomerulopathy or IgA nephropathy. Recognition of this temporal variability is crucial, as all patients in this series recovered with supportive management, underscoring the importance of early biopsy and careful clinicopathological integration in routine clinical practice.</jats:p>