Membranous Nephropathy — Advanced

Membranous nephropathy is defined by diffuse capillary-wall thickening caused by subepithelial immune deposits. On electron microscopy the deposits lie outside the GBM, while light microscopy shows thickened loops and immunofluorescence shows granular immunoglobulin and complement. Mesangial-only disease, linear staining, and isolated crescents indicate different or additional processes.

Anti-PLA2R antibodies are the principal disease-specific circulating marker for primary membranous nephropathy. A positive result supports the diagnosis in the right clinical setting and can help follow immunologic activity, but it does not eliminate the need to consider secondary disease, especially when clinical features are atypical.

Nephrotic membranous nephropathy produces urinary loss of anticoagulant proteins and platelet-hypercoagulability, with risk amplified by severe hypoalbuminemia. Deep-vein thrombosis, pulmonary embolism, and renal-vein thrombosis are important complications; the risk should be assessed alongside bleeding risk before prophylaxis.

Membranous nephropathy may be secondary to malignancy, hepatitis B or C, autoimmune disease such as lupus, or medication exposure. The evaluation should be guided by age, symptoms, examination, serology, imaging, and medication history. A PLA2R result is helpful but is not a substitute for clinical assessment of secondary causes.

Granular capillary-wall staining for IgG and C3 reflects immune-complex deposition along the subepithelial side of the glomerular capillary wall. This contrasts with the smooth linear IgG pattern of anti-GBM disease and the dominant IgA or C3 patterns seen in other glomerular diseases.

Risk assessment is dynamic. Persistent proteinuria, reduced eGFR, low albumin, high or persistent anti-PLA2R activity, and an unfavorable trajectory identify patients at greater risk of progression and may support immunosuppression. No single measurement, including antibody status alone, captures total risk.

Supportive therapy is required regardless of whether immunosuppression is used. It includes blood-pressure and proteinuria reduction, lipid management, edema treatment, vaccination and infection-risk assessment, and individualized thrombosis evaluation. Immunosuppression is reserved for patients whose risk-benefit profile justifies it.

Severe nephrotic syndrome is strongly associated with venous thromboembolism, including renal-vein thrombosis. Acute flank pain, hematuria, or sudden deterioration should prompt urgent evaluation rather than attribution to uncomplicated edema. Imaging and anticoagulation decisions must account for kidney function and bleeding risk.

Systemic lupus features, hypocomplementemia, disease-specific autoantibodies, medication exposure, infection, and malignancy clues favor secondary membranous nephropathy. Primary disease is more likely when the clinical context and immunopathology support it, but no isolated finding should override the full evaluation.

A falling anti-PLA2R titer often represents immunologic response and may precede a measurable fall in proteinuria by months. It is therefore useful for monitoring, but it does not prove complete clinical remission; albuminuria, serum albumin, eGFR, and complications still require follow-up.