Diagnostic pitfall: NSAID-induced membranous nephropathy with PLA2R positivity, IgG1-predominant deposits, C1q positivity, and concurrent acute interstitial nephritis-A case report.
Jingzhen Li, Qianqian Zhang, Zhengyue Chen et al.
✦ AI-curated · Sources linked
Case in brief
A 71-year-old woman with long-term unsupervised NSAID use for polymyalgia rheumatica presented with recurrent nephrotic syndrome and acute kidney injury. She had severe hypoalbuminemia, elevated creatinine, massive proteinuria, and a positive serum anti-PLA2R antibody. Biopsy at relapse showed membranous nephropathy with PLA2R-positive, IgG1-predominant deposits, moderate C1q staining, and severe acute interstitial nephritis, supporting NSAID-induced secondary disease. She achieved clinical remission after NSAID withdrawal and treatment with intravenous methylprednisolone and rituximab, then relapsed after inadvertent NSAID re-exposure.
What made this case unusual
The diagnostic trap was PLA2R positivity in drug-induced secondary membranous nephropathy, alongside IgG1-predominant deposits, C1q positivity, and severe acute interstitial nephritis.
Diagnostic / clinical pearl
A positive anti-PLA2R antibody does not establish primary membranous nephropathy. In suspected drug-associated disease, interpret it alongside medication exposure and biopsy findings, including IgG subclass profile and C1q staining.
Why it matters
The relapse after inadvertent NSAID re-exposure underscores the importance of identifying and avoiding the implicated drug in this case.