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Abstract: FR-PO1054

Comparison Among Dominant C1q Positive Cases Including C1q Nephropathy Classified by Immunofluorescence

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Ono, Erina, Kyoto university Hospital, Kyoto, Japan
  • Endo, Shuichiro, Kyoto university Hospital, Kyoto, Japan
  • Matsubara, Takeshi, Kyoto university Hospital, Kyoto, Japan
  • Yokoi, Hideki, Kyoto university Hospital, Kyoto, Japan
  • Muso, Eri, Kyoto university Hospital, Kyoto, Japan
  • Yanagita, Motoko, Kyoto university Hospital, Kyoto, Japan
Background

Although the disease entity of C1q nephropathy was first described by Jennette and Hipp in 1985, the characteristics of the heterogeneous phenotypes and the pathogenic role of C1q for the disease progression has not been elucidated yet. We analyzed dominant C1q positive renal biopsy specimens to speculate the significance of C1q localization.

Methods

A total of 1763 consecutive patients performed renal biopsy at Kyoto University Hospital from 1982 through 2001 were investigated. We analyzed 34 cases (1.9%) with dominantly C1q-positive staining excluding lupus nephritis, IgA nephropathy, and membranous nephropathy. Next, we classified these patients into three groups; C1q mono-dominant (mC1q) group (n=3) with no immunoglobulin deposition and C1q co-dominant group (total n=31) with IgG (cC1q-IgG) (n=19) or IgM (cC1q-IgM) (n=12).

Results

Precise pathological analysis showed in mC1q group, minor glomerular abnormality in light microscopy (LM), with mesangium localization of C1q with C3d positivity in immunofluorescence microscopy (IF). Apparent electron dense deposit (EDD) and foot process effacement were observed in electron microscopy (EM). CC1q-IgG group revealed variety of glomerulonephritis pattern frequently showing capillary wall involved glomerular lesion such as double contour, subendothelial deposit and crescent formation with high frequency of global sclerosis. C1q localized in capillary wall and mesangium accompanying IgG, and IgM in all cases and additional IgA in 15 cases with strongly positive C3c and C3d in IF. CC1q-IgM group exhibited focal segmental sclerosis and double contour in LM. C1q was positive in mesangium colocalized with IgM and C3d in all but C3c in some in IF. EDD was negative in all 6 cases in EM. Laboratory data revealed cC1q-IgG group included relatively severe cases in creatinine level and hematuria compared with the other two groups.

Conclusion

The hypothesis of glomerular injury through activation of complement system might be applicable via immune complex formation in cC1q-IgG group, directly in mC1q group and not applicable in cC1q-IgM group. The analysis of dominant C1q-positve renal biopsy specimens include several diseases in these case series raises the possibility that current category of C1q nephropathy indicates some specific condition of existing diseases.