Bucillamine-induced membranous nephropathy versus primary membranous nephropathy: comparing pathological features and...

Area of Science:

• Nephrology
• Immunopathology
• Drug-induced diseases

Background:

• Membranous nephropathy (MN) is a leading cause of nephrotic syndrome in adults.
• Distinguishing drug-induced MN from primary MN is crucial for appropriate management.
• Bucillamine, a disease-modifying antirheumatic drug, has been associated with MN.

Purpose of the Study:

• To compare the histopathological features and clinical outcomes of bucillamine-induced membranous nephropathy (BCL-MN) and primary membranous nephropathy (p-MN).
• To identify specific markers that differentiate BCL-MN from p-MN.
• To evaluate the long-term renal prognosis of BCL-MN.

Main Methods:

• Retrospective cohort study of 29 BCL-MN patients and 98 p-MN patients.
• Comparison of kidney biopsy findings, including light microscopy (LM) and immunofluorescence.
• Analysis of clinical course, focusing on proteinuria relapse and estimated glomerular filtration rate (eGFR) decline.

Main Results:

• Histopathological differences observed: BCL-MN showed less spike formation, more stage I cases, predominant IgG1 deposits, and higher prevalence of segmental and para-mesangial deposits.
• Foot process effacement without dense deposits was significantly more common in BCL-MN.
• Clinically, most BCL-MN patients achieved proteinuria resolution after bucillamine discontinuation without eGFR progression.

Conclusions:

• BCL-MN exhibits unique histopathological characteristics compared to p-MN, including distinct immunoglobulin deposition patterns and podocyte injury.
• The clinical course of BCL-MN is generally favorable, with high rates of remission upon drug withdrawal.
• These findings suggest a specific pathogenesis for BCL-MN, potentially linked to bucillamine's mechanism of action.