Abstract: TH-PO200

A Refractory Case of Membranous Nephropathy Concurrent with IgG4-Related Kidney Disease

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports

Authors

  • Arai, Hiroyuki, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Kamimatsuse, Ryo, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Toda, Naohiro, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Nishioka, Keisuke, Osaka red cross hospital, Osaka city, Osaka, Japan
  • Endo, Shuichiro, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Matsubara, Takeshi, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Yokoi, Hideki, Kyoto University Hospital, Kyoto city, Kyoto, Japan
  • Yanagita, Motoko, Kyoto University Hospital, Kyoto city, Kyoto, Japan
Background

IgG4-related kidney disease (IgG4-RKD) is a recently recognized clinical entity characterized by IgG4-positive plasma cell infiltration and characteristic ‘storiform’ fibrosis. Tubulointerstitial nephritis is the most common finding, which responds well to corticosteroid therapy. However, it is uncertain whether the treatment for IgG4-RKD is equally effective for membranous nephropathy (MN), which occasionally coincides with IgG4-RKD. We present a refractory case of IgG4-RKD accompanied with MN, which warrants the combination therapy of prednisone (PSL) and cyclosporine (CyA).

Methods

A 58-year-old male was referred to our hospital for recently diagnosed nephrotic syndrome. He had a history of autoimmune pancreatitis (AIP), and was maintained on PSL 10 mg/day. Laboratory results revealed serum albumin 2.2 g/dL, creatinine 0.80 mg/dL, IgG4 473 mg/dL, and urinary protein 13.6 g/gCr. Anti-PLA2R antibody was undetectable. Renal biopsy revealed tubulointerstitial lymphoplasmacytic infiltration and storiform fibrosis with increased ratio of IgG4/IgG positive plasma cells (44.8%), predominant subepithelial granular deposits of IgG1 and IgG2 in glomeruli, and electron dense deposits in subepithelial and subendothelial regions along glomerular basement membrane. As other causes of secondary MN were excluded, we diagnosed secondary MN concurrent with IgG4-RKD. Although PSL was increased to 35 mg/day, proteinuria did not resolve. CyA was initiated, and urinary protein started decreasing. While serum IgG4 level increased by tapering PSL, urinary protein remained suppressed. After 1 year of follow-up, urinary protein decreased to 0.34 g/gCr and AIP did not recur under PSL 12.5 mg/day.

Conclusion

Renal biopsy findings and negative anti-PLA2R antibody argued for secondary MN concurrent with IgG4-RKD. While PSL was effective for the extrarenal lesion of IgG4-RKD, proteinuria was refractory to PSL and the addition of CyA was required. Generally IgG4-RKD responds well to PSL, in great contrast to our case. Moreover, our case is interesting in that serum IgG4 level did not correlate with proteinuria, indicating that serum IgG4 level does not reflect the activity of MN. These findings suggest that the underlying etiology of secondary MN concurrent with IgG4-RKD is different from other lesion of IgG4-RKD.