Idiopathic fibrillary glomerulonephritis in pediatric patients: addressing treatment challenges in a 12-year-old girl.

A 12-year-old girl presented with proteinuria and peripheral edema. Initial evaluation did not identify a clear underlying etiology. Upon the diagnosis of nephrotic syndrome, corticosteroid therapy was initiated. However, the therapeutic response was suboptimal, with persistent proteinuria, the onset of de novo microhematuria, and progressive kidney dysfunction. A kidney biopsy was performed, which led to the diagnosis of fibrillary glomerulopathy, a rare pediatric condition characterized histologically by the presence of fibrillary deposits and positive immunostaining for DNAJB9. There is no established effective treatment for this condition. In our case, the patient was treated with antiproteinuric and calcineurin inhibitors, resulting in complete resolution of microhematuria, normalization of kidney function, and substantial improvement in proteinuria.