Endocapillary proliferative glomerulonephritis with crescent formation and concurrent tubulointerstitial nephritis complicating retroperitoneal fibrosis with a high serum level of IgG4.

Renal lesions of IgG4-related disease have been reported recently. Most of them are tubulointerstitial nephritis, and a definite glomerulonephritis complicating IgG4-related disease is very rare. We report here a case of definite glomerulonephritis and concurrent tubulointerstitial nephritis complicating retroperitoneal fibrosis with a high serum level of IgG4. A 68-year-old Japanese woman was referred to our hospital for investigation of anasarca. We diagnosed her disease as a nephrotic syndrome and left hydroureteronephrosis due to retroperitoneal fibrosis. Her laboratory data revealed a high serum level of IgG4, renal injury, hypoproteinemia, hypocomplementemia, a positive finding of circulating immunocomplex (CIC), and negative findings ofautologous antibodies suggesting systemic lupus erythematosus (SLE) or Sjögren's syndrome (SS). A diagnosis of SLE or SS could not be made clinically. Right renal biopsy revealed endocapillary proliferative glomerulonephritis with crescent formation and concurrent tubulointerstitial nephritis. Infiltration of plasma cells in interstitium was more conspicuous than seen with ordinary tubulointerstitial nephritis, and in most of them IgG4 was positive. We placed a percutaneous nephrostomy catheter in her left kidney, and prescribed prednisolone and cyclosporine. The responses to prednisolone and cyclosporine therapies were very good. Further studies are needed to clarify the relationship between glomerulonephritis and IgG4-related disease. However, when considering renal lesions of IgG4-related disease, we think that hypocomplementemia, a positive finding of CIC, negative findings of autologous antibodies suggesting SLE or SS, conspicuous interstitial infiltration of IgG4-positive plasma cells, and a good response to steroid or immunosuppressant therapy are key points.