Fibrillary glomerulonephritis related to serum fibrillar immunoglobulin-fibronectin complexes

Fibronectin glomerulopathy with monoclonal gammopathy responding to bortezomib plus dexamethasone: a case report

BACKGROUND

Fibronectin glomerulopathy is a rare, familial glomerular disease characterized by mesangial fibronectin deposition in the glomeruli. It is caused by the genetic defect in fibronectin and does not involve the activation of the immune system. Therefore, glomerular immunoglobulin and complement staining is generally absent or weak. Monoclonal gammopathy (MG) is an increasing cause of renal lesion, featured by light chain (κ or λ) and/or heavy chain restriction in glomeruli. Herein, we report a case of fibronectin glomerulopathy presenting as strong IgA and C3 immunostaining in renal biopsy, concomitant with monoclonal gammopathy (monoclonal IgA κ).

CASE PRESENTATION

A 44-year-old female was admitted to our hospital for one-month pedal edema. The serum albumin of 19.6 g/l, and the 24-h urine protein was 15.092 g. Immunofixation electrophoresis displayed monoclonal IgA. The renal biopsy showed the mesangial deposits positive for IgA (3+) and C3 (3+) and also for IgG (2+), IgM (2+), and C1q (2+) IF microscopy. In addition, the staining intensity of light chain κ was slight greater than that of light chain λ. The glomerular deposits were strongly positive by FN by immuohistochemistry. The patient was treated with bortezomib, dexamethasone in combination with cyclophosphamide and gained partial remission.

CONCLUSION

We present the first FNG patient with strong IgA and C3 immunostaining in the context of monoclonal IgA κ in the circulation. Perhaps FNG, monoclonal IgA κ and immune activation are potentially interplayed and eventually induce renal injuries.

Fibrillary Glomerulonephritis: An Update

Fibrillary glomerulonephritis (FGN) is a rare proliferative form of glomerular disease characterized by randomly oriented fibrillar deposits with a mean diameter of 20 nm. By immunofluorescence (IF), the deposits stain for IgG, C3, and κ and λ light chains, suggesting that the fibrils may be composed of antigen-antibody immune complexes. A recent major advance in our understanding of the pathogenesis of FGN resulted from the discovery that a major component of the fibrils is DNA-J heat-shock protein family member B9 (DNAJB9), and immunohistochemical staining for DNAJB9 now makes it possible to diagnose FGN in the absence of ultrastructural evaluation. FGN has a poor prognosis, treatment options are currently limited, and transplant recurrence is not uncommon.

Immunotactoid Glomerulopathy and Cryoglobulinemic Nephropathy: Two Entities with Many Similarities. A Unified Conceptual Approach

Immunotactoid glomerulopathy is a rare disorder that has been characterized at the ultrastructural level. Due to its rarity, there are few comprehensive studies relating to this disorder. Electron microscopy essentially characterizes this disease. The glomerular electron dense deposits which are typical of this condition consist of aggregates of highly organized microtubular structures of various diameters, but generally measuring 30-50 nm in width with a propensity to dispose themselves in parallel bundles intersecting in different planes. This study compares a large series of patients with cryoglobulinemic nephropathy with a series of patients with immunotactoid glomerulopathy to address whether there may be similarities that warrant considering these two entities part of a spectrum. This study reviews the clinicopathologic features of both entities and emphasizes ultrastructural findings that characterize them. Significant immunomorphologic overlap was found when these two disorders were compared in this study. There were also striking similarities in clinical presentation/behavior, laboratory findings and prognosis. Proteomic analysis has also demonstrated similar spectra for both entities. We postulate that immunotactoid glomerulopathy and cryoglobulinemic nephropathy are part of the spectrum of renal manifestations in patients with circulating cryoglobulins and renal disease.

Pathology of glomerular deposition diseases

In routine diagnosis on renal biopsy, one of the confusing fields for pathological diagnoses is the glomerulopathies with fibrillary structure. The primary glomerulopathies with a deposit of ultrastructural fibrillary structure, which are negative for Congo-red stain but positive for immunoglobulins, include fibrillary glomerulonephritis and immunotactoid glomerulopathy. Several paraproteinemias including cryoglobulinemia, monoclonal gammopathy, and light chain deposition disease as well as hematopoietic disorders including plasmacytoma, plasma cell dyscrasia, and B cell lymphoproliferative disorders involve glomerulopathy with an ultrastructural fibrillary structure. A rare glomerulopathy with fibrillary structure that stains negative for Congo-red as well as for immunoglobulins has been also reported. The pathological diagnoses of these glomerulopathies can include either glomerular diseases, or paraproteinemic diseases, or hematopoietic diseases. The terminology is still confusing when glomerular diseases can be combined with paraproteinemic diseases and/or hematopoietic diseases. Therefore, the generic term, 'glomerular deposition disease' (GDD), has been proposed by pathologists with a requirement for clinicians to detect autoantibodies, paraproteins as well as to carry out a bone marrow check. An attempt has been made to rearrange the diseases with related disorders of fibrillary deposits, based on detailed clinical and pathological finding and to elucidate the correlation between GDD, paraproteinemia, and hematopoietic disorder.

Fibrillary and immunotactoid glomerulonephritis: Distinct entities with different clinical and pathologic features

BACKGROUND

Controversy surrounds the relatedness of fibrillary glomerulonephritis (FGN) and immunotactoid glomerulonephritis (IT).

METHODS

To better define their clinicopathologic features and outcome, we report the largest single center series of 67 cases biopsied from 1980 to 2001, including 61 FGN and 6 IT. FGN was defined by glomerular immune deposition of Congo red-negative randomly oriented fibrils of < 30 nm (mean, 20.1 +/- 0.4 nm). IT was defined by glomerular deposition of hollow, stacked microtubules of > or = 30 nm (mean, 38.2 +/- 5.7 nm).

RESULTS

FGN comprised 0.6% of total native kidney biopsies and IT was tenfold more rare (0.06%). Deposits in FGN were immunoglobulin G (IgG) dominant and polyclonal in 96%. IgG subtype analysis in 19 FGN cases showed monotypic deposits in four (two IgG1 and two IgG4) and oligotypic deposits in 15 (all combined IgG1 and IgG4). In IT, deposits were IgG dominant in 83% and monoclonal in 67% (three IgG1 kappa and one IgG1 lambda). FGN patients were a mean age of 57 years, 92% were Caucasian, and 39% were male. At biopsy, FGN patients had the following clinical characteristics (mean, range): creatinine 3.1 mg/dL (0.5 to 14), proteinuria 6.5 g/day (0.8 to 25), 60% microhematuria, and 59% hypertension. Histologic patterns of FGN were diverse, including diffuse proliferative glomerulonephritis (DPGN) (nine cases), membranoproliferative glomerulonephritis (MPGN) (27 cases), mesangial proliferative/sclerosing (MES) (13), membranous glomerulonephritis (MGN) (four), and diffuse sclerosing (DS) (eight). The more proliferative (MPGN and DPGN) and sclerosing (DS) forms presented with a higher creatinine and greater proteinuria compared to MES and MGN. Median time to end-stage renal disease (ESRD) was 24.4 months for FGN and mean time to ESRD varied by histologic subtype: DS 7 months, DPGN 20 months, MPGN 44 months, compared to MES 80 months and MGN 87 months. There was no statistically significant effect of immunosuppressive therapy (given to 36% of FGN patients). By Cox regression (hazard ratio, confidence interval, P value), independent predictors of progression to ESRD were creatinine at biopsy [2.05 (1.55 to 2.72) P < 0.001] and severity of interstitial fibrosis [2.01 (1.05 to 3.85) P = 0.034]. Although IT had similar presentation, histologic patterns, and outcome compared to FGN, it had a greater association with monoclonal gammopathy (P = 0.014), underlying lymphoproliferative disease (P = 0.020), and hypocomplementemia (P = 0.032).

CONCLUSION

FGN is an idiopathic condition characterized by polyclonal immune deposits with restricted gamma isotypes. Most patients present with significant renal insufficiency and have a poor outcome despite immunosuppressive therapy, and outcome correlates with histologic subtype. By contrast, IT often contains monoclonal IgG deposits and has a significant association with underlying dysproteinemia and hypocomplementemia. Differentiation of FGN from the much more rare entity IT appears justified on immunopathologic, ultrastructural, and clinical grounds.

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.

Glomerulonephritis with microtubular deposits associated with cryoglobulinemia and chronic active hepatitis

A 65-year-old-woman presented with edema, ascites, proteinuria and abnormal liver function tests. A small amount of mixed cryoglobulin was detected in her serum. Liver biopsy revealed mild chronic active hepatitis, but tests for hepatotropic viral infection were negative. Electron microscopy of the renal biopsy revealed glomerular electron-dense deposits that contained numerous tubular structures. Renal amyloidosis and light chain deposition disease were ruled out by appropriate histological techniques. The ultrastructural findings of renal biopsy suggested either cryoglobulinemic glomerulonephritis or immunotactoid glomerulopathy. Although the exact interrelationship among the peculiar glomerulopathy, cryoglobulinemia and chronic active hepatitis in the present case remains undetermined, this report enlarges the spectrum of glomerulopathy characterized by extracellular deposition of microtubules.

Fibrillary glomerulonephritis: a report of 2 cases with extensive glomerular and tubular deposits

Deposition of nonamyloid fibrillary material in glomeruli is well known. It is, however, unusual to find these fibrils in the tubular basement membranes and unprecedented to have fibrils of different sizes in the same patient. We present 2 cases with nephrotic range proteinuria with evidence of renal insufficiency. In both cases, strong, polyclonal immunoglobulin (Ig)G with C3 deposits were shown in the glomeruli and along tubular basement membranes. Ultrastructurally, the first case had 28-nm fibrils deposited extensively in the glomeruli and along tubular basement membranes. The second case had 30-nm fibrils in the glomeruli and 15-nm fibrils in the tubules. In both cases, the fibrils did not react with the regular amyloid stains. These findings are used to support the view that fibrillary glomerulopathy is not a disease, but rather the morphologic expression of an etiologically diverse group of diseases as yet incompletely defined.

Fibrillary and immunotactoid glomerulopathies

There is sufficient clinical and morphological evidence to suggest that Fibrillary Glomerulonephritis (FGN) and Immunotactoid (IT) Glomerulopathy are two different diseases. Is still open to debate if IT glomerulopathy is a distinct entity or is strictly associated with a spectrum of systemic syndromes ("forme fruste" of Cryoglobulin and paraprotein associated diseases). Further studies about pathogenetic mechanisms of fibril or microtubule formation may allow a better understanding of these diseases.

A 51-year-old woman with nephrotic syndrome, hematuria, and renal insufficiency

This case illustrates the utility of all modalities of the renal biopsy in arriving at a correct diagnosis in an adult patient with nephrotic syndrome. Unlike the clinical situation in children, where minimal change disease is presumed to underlie the nephrotic syndrome unless the patient shows steroid resistance, the list of differential diagnosis of nephrotic syndrome in the adult is lengthy. The renal biopsy is essential in establishing the specific diagnosis. We discuss the diagnostic approach in an adult patient with a relatively uncommon disease causing the common manifestations of nephrotic syndrome, hematuria and renal insufficiency.