Fibrillary glomerulonephritis and immunotactoid (microtubular) glomerulopathy are associated with distinct immunologic features.
BACKGROUND
The clinical relevance of distinguishing two types of glomerulonephritis (GN) with non-amyloid organized immunoglobulin (Ig) deposits-fibrillary GN (FGN) and immunotactoid (microtubular) GN (IT/MTGN)-on the basis of ultrastructural organization, is debated.


METHODS
Twenty-three patients with organized glomerular Ig deposits were classified into two groups based on the fibrillar or microtubular ultrastructural appearance of the deposits. Kidney biopsy samples were studied by immunofluorescence microscopy, using anti-light chain conjugates (all cases) and anti-IgG subclass conjugates (13 patients). In each group, we studied clinicopathological features, associated monoclonal gammapathy (detected by immunoelectrophoresis and/or immunoblot) or B-cell lymphoproliferative disease, effects of chemotherapy and long-term renal outcome.


RESULTS
In 14 IT/MTGN and 9 FGN patients, clinical symptoms [hypertension, nephrotic syndrome (NS) and hematuria] and the mean diameters of the substructures were similar. In 13 IT/MTGN patients, glomerular (IgG1, 2 or 3) deposits were monotypic (kappa, 7 cases; lambda, 6 cases). Glomerular deposits were associated with a monoclonal Ig of the same isotype in eight patients, detected in the serum (5 cases), and/or in the cytoplasm of lymphocytes (4 cases), and with lymphoproliferative disease in seven patients. The ultrastructural features of monoclonal Ig inclusions in lymphocytes were similar to those of glomerular microtubular deposits. In contrast, none of the FGN patients presented lymphoplasmocytic proliferation or paraproteinemia. Glomerular Ig deposits were polyclonal in eight cases and contained IgG4 in all three cases studied. Although patient and renal survival did not differ significantly between the two groups, chemotherapy led to remission of NS in ten IT/MTGN patients, with parallel improvement in hematological parameters.


CONCLUSIONS
The identification of ultrastructural patterns in these nephropathies is important. GN with organized microtubular monoclonal deposits (GOMMID) probably accounts for a large proportion of immunotactoid (microtubular) GN cases.
Bridoux
Frank
F
Department of Nephrology, and Laboratory of Immunology and Immunopathology(CNRS ESA 6031), University Hospital, Poitiers, France. f.bridoux@chu-poitiers.fr
Hugue
Valerie
V
Coldefy
Olivier
O
Goujon
Jean-Michel
JM
Bauwens
Marc
M
Sechet
Anne
A
Preud'Homme
Jean-Louis
JL
Touchard
Guy
G
D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000032:analysis; D000970:Antineoplastic Agents / Q000008:administration & dosage; D001706:Biopsy; D005260:Female; D005921:Glomerulonephritis / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology*; D006510:Hepatitis B Antibodies / Q000032:analysis; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy / Q000276:immunology / Q000473:pathology; D008228:Lymphoma, Non-Hodgkin / Q000188:drug therapy / Q000276:immunology / Q000473:pathology; D008297:Male; D008870:Microtubules / Q000473:pathology* / Q000648:ultrastructure; D008875:Middle Aged; D010265:Paraproteinemias / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology*; D016896:Treatment Outcome
D000305:Adrenal Cortex Hormones; D000974:Antibodies, Antinuclear; D000970:Antineoplastic Agents; D006510:Hepatitis B Antibodies; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents