Immunotactoid Glomerulopathy

Immuotactoid Glomerulopathy (Fibrillary Glomerulonephritis)

“…Finally, there is no pathogenic or biochemical basis to justify such a division. Therefore, in our view, on the basis of the existing literature, there is no compelling reason to diagnose ITG and FGN separately on the basis of morphology alone, because it has not been demonstrated clearly that the ultrastructural features have significant pathogenic or clinical implications (8). As a result, we agree with the conclusion of Brady that "it would be folly to subclassify patients on the basis that the variants look different" (4).…”

“…Proliferative glomerulonephritis with cellular and fibrocellular crescents and segmental necrotizing lesions have been described in up to 30% of patients (4,5,9,22,23). However, we have not seen these lesions in ITG when systemic diseases such as cryoglobulinemia, paraproteinemia, and SLE have been excluded (6,8,16). Most important, the glomeruli, tubulointerstitium, and vessels are negative for amyloid by Congo red and thioflavin-T stains.…”

“…However, in almost 50% of cases, the fibril diameters have a mean value of 18 to 22 nM ( Figure 2B) (8). Although there is variability of fibril size among cases, the fibrils in a given case are remarkably consistent in appearance wherever they appear in the glomerulus.…”

“…The Ig class that is seen in the majority of cases is IgG (IgG 94%, IgA 60%, IgM 29%), and in 80% of cases, both and light chains are seen. Despite the absence of a paraprotein, monoclonal Ig deposits have been seen in approximately 20% of cases of ITG studied with light-chain antisera, and lightchain restriction was present in all cases, usually in combination with IgG heavy chain (8). A study of IgG subgroups found IgG4 as the dominant subclass with weak staining for IgG1 and absent IgG2 and IgG3 (9), and monoclonal IgG3 was reported in one case, not associated with a paraproteinemia, with 35 nM microtubular deposits (2).…”

“…By light microscopy, mesangial expansion by periodic acid-Schiffpositive material with only a mild mesangial hypercellularity is observed in up to 95% of cases (4,8,9). Glomerular capillary wall pathology also is observed in 95% of cases, may be focal or diffuse, and consists of thickening and complex staining patterns that are seen with methenamine silver-periodic acidSchiff (Jones) stain, including reticular patterns, spikes, and double contours.…”