Severe Nephrotic Syndrome Secondary to Primary Membranous Nephropathy in an Adult

Abstract

Introduction: Primary membranous nephropathy is one of the leading causes of nephrotic syndrome in adults and represents a diagnostic challenge due to the need to exclude multiple secondary etiologies. Presentation of case: We report the case of a 39-year-old man who presented with anasarca, oliguria, and exertional dyspnea associated with massive proteinuria (23.8 g/24 h) and severe hypoalbuminemia. Given the complexity of the presentation, an extensive diagnostic workup was performed to rule out autoimmune diseases, malignancies, amyloidosis, and monoclonal gammopathies through immunological testing, biopsies, and immunohistochemical studies. Renal biopsy confirmed membranous nephropathy, and subsequent detection of anti-PLA2R antibodies established its primary origin. The patient initially received the modified Ponticelli regimen; however, disease activity persisted, leading to the initiation of rituximab as second-line therapy. Conclusion: This case highlights the importance of differential diagnosis and etiological confirmation in the management of primary membranous nephropathy.