Nephrin-IgG co-localization expression in pediatric steroid-resistant nephrotic syndrome: a case series from Indonesia.

Steroid-resistant nephrotic syndrome (SRNS) remains a major clinical challenge due to its heterogeneous etiologies and poor response to conventional immunosuppressive therapy. Anti-nephrin IgG has been associated with podocyte injury and proteinuria, suggesting a potential pathogenic role in SRNS. This case series was conducted to present real-world data on the evaluation of nephrin-IgG immunofluorescence colocalization in pediatric SRNS in a low-resource setting, and to examine whether this approach may inform treatment selection in routine clinical practice. We describe four pediatric patients with SRNS who underwent kidney biopsy following persistent proteinuria despite immunosuppressive therapy. Case 1 showed severe hypoalbuminemia and anasarca with preserved renal function after full dose steroid; Case 2 remained edematous with nephrotic range proteinuria after seven cycle of cyclophosphamide; Case 3 progressed to chronic kidney disease despite cyclophosphamide and mycophenolate mofetil; Case 4 had normal kidney function and no edema, despite steroid resistant. Nephrin-IgG co-localization was observed in all cases. Clinical outcomes were heterogeneous, and assessment of treatment response was limited by resource constraints and loss to follow-up. These findings are exploratory in nature and suggest the potential applicability of nephrin-IgG co-localization in a low-resource setting, warranting further investigation.