Tiopronin-induced Membranous Nephropathy Presenting with IgG4-predominant Staining Pattern

Area of Science:

• Nephrology
• Immunology
• Pharmacology

Background:

• Cystinuria is a genetic disorder of amino acid transport.
• Tiopronin is a primary treatment for cystinuria.
• Nephrotic syndrome (NS) and membranous nephropathy (MN) are potential adverse effects of medications.

Purpose of the Study:

• To report a case of secondary nephrotic syndrome and membranous nephropathy induced by tiopronin.
• To investigate the immunopathological characteristics of tiopronin-induced membranous nephropathy.
• To suggest a novel etiology for drug-induced membranous nephropathy.

Main Methods:

• Clinical case presentation of a patient with cystinuria.
• Laboratory analysis including serum albumin and urinary protein levels.
• Kidney biopsy with immunofluorescence for immunoglobulin deposition.

Main Results:

• A 41-year-old woman developed NS and MN after tiopronin administration.
• Remission of NS was achieved after tiopronin cessation.
• Kidney biopsy revealed membranous nephropathy with significant immunoglobulin G4 (IgG4) deposition.

Conclusions:

• Tiopronin can induce secondary nephrotic syndrome and membranous nephropathy.
• This case presents a unique IgG4-dominant pattern in tiopronin-induced MN, differing from previous reports.
• This finding suggests a novel immunopathological mechanism for tiopronin-induced membranous nephropathy.