Clinical and pathologic features of fibrillary glomerulonephritis

Familial Mediterranean fever, inflammation and nephrotic syndrome: fibrillary glomerulopathy and the M680I missense mutation

BACKGROUND

Familial Mediterranean fever (FMF) is an autosomal recessive disease characterized by inflammatory serositis (fever, peritonitis, synovitis and pleuritis). The gene locus responsible for FMF was identified in 1992 and localized to the short arm of chromosome 16. In 1997, a specific FMF gene locus, MEFV, was discovered to encode for a protein, pyrin that mediates inflammation. To date, more than forty missense mutations are known to exist. The diversity of mutations identified has provided insight into the variability of clinical presentation and disease progression.

CASE REPORT

We report an individual heterozygous for the M680I gene mutation with a clinical diagnosis of FMF using the Tel-Hashomer criteria. Subsequently, the patient developed nephrotic syndrome with biopsy-confirmed fibrillary glomerulonephritis (FGN). Further diagnostic studies were unremarkable with clinical workup negative for amyloidosis or other secondary causes of nephrotic syndrome.

DISCUSSION

Individuals with FMF are at greater risk for developing nephrotic syndrome. The most serious etiology is amyloidosis (AA variant) with renal involvement, ultimately progressing to end-stage renal disease. Other known renal diseases in the FMF population include IgA nephropathy, IgM nephropathy, Henoch-Schönlein purpura as well as polyarteritis nodosa.

CONCLUSION

To our knowledge, this is the first association between FMF and the M680I mutation later complicated by nephrotic syndrome and fibrillary glomerulonephritis.

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.

Identification of IgG subclasses and C-reactive protein in lupus nephritis: the relationship between the composition of immune deposits and FCgamma receptor type IIA alleles

OBJECTIVE

To characterize the subclass composition of IgG deposited in lupus glomeruli, to examine its relationship to allelic polymorphisms of IgG receptors (Fcgamma receptors [FcgammaR]), and to determine whether C-reactive protein (CRP), a ligand for FcgammaRIIa, is present in these immune deposits.

METHODS

Renal biopsy samples from 80 patients with lupus nephritis were examined by light microscopy and indirect immunofluorescence with IgG-subclass-specific monoclonal antibodies. FcgammaRIIA genotypes were determined using allele-specific polymerase chain reaction. Immunostaining for CRP was performed on lupus and nonlupus glomerulonephritis specimens.

RESULTS

IgG2 and IgG3 were the predominant subclasses in immune deposits in all World Health Organization classes of nephritis. The frequency of genotypes containing the low-binding IgG2 allele, FcgammaRIIa-R131, was significantly greater than expected in patients with class III or class IV nephritis and in patients with intense IgG2 deposition. CRP, a ligand with particular affinity for FcgammaRIIa-R131, was consistently present in the renal immune deposits of lupus nephritis specimens.

CONCLUSION

FcgammaRIIA genes are associated with proliferative renal disease and may contribute to disease pathogenesis. FcgammaRIIa-R131, the variant with low affinity for IgG2, has high affinity for CRP. Thus, FcgammaRIIa-R131 may contribute to impaired removal of circulating immune complexes, as well as efficiently triggering phagocyte activation and the release of inflammatory mediators within glomeruli.

A case of idiopathic nodular glomerulosclerosis mimicking diabetic glomerulosclerosis (Kimmelstiel-Wilson type)

A case of idiopathic nodular glomerulosclerosis mimicking diabetic Kimmelstiel-Wilson glomerulopathy is reported. The patient was a 45-year-old man suffering from nephrotic syndrome. Light and electron microscopy revealed diffuse and nodular glomerulosclerosis indistinguishable from diabetic nodular glomerulosclerosis. Diabetes mellitus, however, had been excluded both by extensive clinical and by laboratory investigation. The differential diagnosis also included amyloidotic and non-amyloidotic fibrillary glomerulopathy, light chain glomerulopathy, collagen type III disease, immunotactoid glomerulopathy, and the sclerosing variant of membranoproliferative glomerulonephritis. Immunohistochemistry and ultrastructural investigations, however, excluded these entities, and the diagnosis of idiopathic nodular glomerulosclerosis was made. This variant has to be included in the differential diagnosis of nodular glomerulopathy associated with nephrotic syndrome.

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.

Fibrillary glomerulonephritis: early diagnosis associated with steroid responsiveness

Patients with fibrillary glomerulonephritis usually present with nephrotic proteinuria, microscopic hematuria, impaired renal function, and hypertension; 50% develop end-stage renal disease within a few years. There is no known effective therapy for fibrillary glomerulonephritis. We describe three patients with biopsy-proven fibrillary glomerulonephritis, in whom pathognomonic fibrillar deposits of 20-nm diameter were seen by electron microscopy. All patients had nephrotic syndrome and normal renal function at the time of diagnosis. They were treated initially with prednisone, 1 mg/kg body weight, then tapered individually according to the clinical course. Additional therapy consisted of an angiotensin-converting enzyme inhibitor and diuretics. Proteinuria disappeared in two of three patients after 9 and 12 months of therapy. In one patient, proteinuria was reduced from 7.49 mg/mg creatinine to 0.63 mg/mg creatinine after 6 months of treatment. The kidney function remained normal in all three cases. Two patients are now free of steroid therapy for 9 and 6 months. They show no signs of recurrence of kidney disease and have normal renal function without significant proteinuria. Steroid therapy in patients with biopsy-proven fibrillary glomerulonephritis, starting with prednisone, 1 mg/kg body weight, and tapered individually according to the clinical course, is a promising strategy. Early start of treatment in patients with preserved renal function seems to be crucial for a favorable outcome.

Fibrillary glomerulonephritis associated with crescents as a therapeutic challenge

Most cases of fibrillary glomerulonephritis (FG) terminate in end-stage renal disease within a few years. We report on two female patients (41 and 50 years old) with the diagnosis of FG associated with crescentic glomerulonephritis, a combination found in 20% to 25% of cases of FG. A broad spectrum of infectious disease and systemic immunologic disorders could be ruled out by specific assays. Both patients had severely impaired renal function, nephrotic syndrome, and hypertension. Based on the biopsy finding with necrotizing FG, treatment was started with corticosteroids and cyclophosphamide. In both patients, renal function recovered markedly within 6 months of treatment, in one case remaining stable for 3.5 years. Whether or not cyclophosphamide treatment changed the course of the FG itself or counteracted the acute crescentic process cannot be determined from these two patients. Based on these promising preliminary findings and the poor prognosis of FG, however, we recommend cyclophosphamide treatment of patients with FG and additional crescentic glomerulonephritis. For a systematic evaluation of the therapeutic options in FG, a multicenter clinical trial should be conducted.

Mesangial IgG glomerulonephritis: a distinct type of primary glomerulonephritis

Fourteen cases of mesangial IgG glomerulonephritis characterized by exclusive or predominant mesangial IgG deposits are reported. The median age at onset was 19 yr (range, 13 to 47 yr). No patient exhibited evidence of systemic lupus erythematous or other systemic diseases. Proteinuria was present in all cases (median, 2.4 g/d; range, 1 to 13 g/d), microscopic hematuria in 12 cases, and macroscopic hematuria in two cases. Five patients were hypertensive at the time of referral. In all cases, renal biopsies revealed mesangial IgG deposits and varying degrees of mesangial matrix expansion, in the absence of significant mesangial cell proliferation. Complement component (mainly C3) deposits were present in virtually all cases. Subepithelial deposits were also noted in nine cases. IgG deposits were polyclonal and consisted mainly of IgG1 and IgG3 subclasses. In electron-microscopic analyses, deposits were electron dense and granular. Treatment was purely supportive. After a mean follow-up period of 11 yr, seven patients had experienced progression to chronic renal failure, including four who had reached end-stage renal failure. Three patients exhibited persistently normal renal function. For one patient, a symptomatic recurrence of mesangial IgG deposits in the renal graft was diagnosed 4 yr after renal transplantation. Such a recurrence highlights the specificity of this type of glomerulonephritis. Mesangial IgG glomerulonephritis is a distinct, albeit rare, type of glomerulonephritis that exhibits far from benign outcome and may recur in renal transplants.

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.

A case of fibrillary glomerulonephritis with linear immunoglobulin G staining of the glomerular capillary walls

We report a case of crescentic glomerulonephritis that presented with extensive crescent formation and fibrinoid necrosis in the glomeruli. Immunofluorescence staining was strongly positive for linear and pseudolinear staining of the capillary walls for immunoglobulin G (IgG) in the absence of significant mesangial staining. Histologic examination and immunofluorescence staining suggested a diagnosis of anti-glomerular basement membrane disease. However, electron microscopy showed the presence of numerous fibrillary deposits in the subepithelial areas of the glomerular capillary walls, supporting the diagnosis of fibrillary glomerulonephritis. Test results for circulating anti-glomerular basement membrane antibodies were negative. We report this interesting case to illustrate the point that fibrillary glomerulonephritis should be considered in the differential diagnosis of crescentic glomerulonephritis with linear and pseudolinear IgG deposits within the capillary walls. In such cases, electron microscopy is critical in differentiating the cause of crescentic glomerulonephritis.

Immunotactoid glomerulopathy characterized by steroid-responsive massive subendothelial deposition

We report a case of immunotactoid glomerulopathy with unique histologic findings in serial biopsies. A 73-year-old man complained of developing general edema. Laboratory data on admission presented moderate renal dysfunction with nephrotic syndrome. There was no evidence of systemic disease that might cause secondary glomerulopathy. Light microscopy of the renal specimen revealed lobulation of glomerular tufts and massive endothelial deposition of hyaline-like periodic acid-Schiff-positive substance with neutrophilic infiltration. The deposits were positive for immunoglobulin by immunohistochemical stains but negative for Congo red stain. Electron microscopy disclosed the deposition of microtubular structure (60 nm in diameter) predominantly in the subendothelial area and to some extent in the subepithelial and mesangial areas. Some of the tubules were extremely large (100 to 130 nm in diameter) and displayed a unique scroll structure in cross-section. The patient was treated with two sessions of plasma exchange and subsequent oral prednisolone (30 mg/d). Proteinuria and renal dysfunction improved significantly in the following 2 months. Second and third renal biopsies revealed disappearance of the deposit along with the improvement of proteinuria and renal dysfunction. Because similar microtubular structures were found in neutrophils in the glomerulus as well as in the urinary sediment, phagocytosis was suggested as a possible mechanism for removal of the deposit.

Glomerulopathies with fibrillary deposits

Renal diseases involving glomerular deposits of fibrillary material are an important diagnostic challenge for the ultrastructural pathologist. Two primary disorders of this type, termed "fibrillary glomerulonephritis" (characterized by fibrils measuring approximately 20 nm in diameter) and "immunotactoid glomerulopathy" (characterized by larger, microtubular deposits), have been described. The possible relatedness of these two disorders and their potential association with other systemic illnesses are subjects of current debate. Other multisystemic diseases, including amyloidosis and various forms of cryoglobulinemia, can also present with fibrillary or microtubular deposits in the kidney. Five cases are presented in which fibrillar or microtubular structures were identified in renal biopsies by ultrastructural examination. The distinction between fibrillary glomerulonephritis, immunotactoid glomerulopathy, and other processes that have similar ultrastructural features are discussed.

Intraglomerular monocyte infiltration and immune deposits in diffuse lupus glomerulonephritis

Previous studies have suggested that separately, glomerular monocyte (MO) infiltration and persistent glomerular immune deposits have opposite prognostic implications in lupus nephritis (LN). To see whether these pathological variables are inversely related, 37 renal biopsy specimens from 37 patients with diffuse proliferative LN were assessed histologically for activity index, chronicity index, and mean glomerular deposit score per biopsy (deposit index [DI]); the latter was determined semiquantitatively on a scale of 0 to 4.0. Frozen sections were double immunolabeled for immunoglobulin G (IgG) and CD68, a marker for MOs. For each glomerulus in each biopsy specimen, the number of CD68+ cells was counted and the amount of IgG scored semiquantitatively on a scale of 0 to 4.0. For each biopsy specimen, the mean number of MOs per glomerular cross-section (MO index [MOI]) was calculated. Linear regression analysis showed a moderately strong inverse correlation between individual glomerular IgG deposit score and individual glomerular MO count (r = -0.447; P < 0.0001), a weaker but significant inverse correlation between DI and MOI (r = -0.350; P = 0.0389), and a positive correlation between the DI determined histologically in each case and the corresponding DI scored on the immunolabeled sections (r = 0.534; P = 0.0105). The results indicate that the amount of glomerular deposit and the extent of glomerular MO infiltration are inversely related in LN.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

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.

Glomerular pathology: recent advances

The last decade has seen significant advances in the fields of cellular and molecular biology and pathology. These have contributed to our understanding of the mechanisms of glomerular disease and indicate possible novel approaches to therapy. This review discusses recent insights into the pathogenesis of glomerular disease, with consideration of the roles of intrinsic glomerular cells, infiltrating inflammatory cells, circulating permeability factors, and antibodies, and recent advances in the molecular pathology of the glomerular basement membrane. Changes in the perception of some well-established glomerular entities such as focal segmental glomerulosclerosis are considered. In addition, a number of newly-recognized specific glomerulopathies including collapsing glomerulopathy, fibrillary and immunotactoid glomerulopathy, fibronectin glomerulopathy, and collagenofibrotic glomerulopathy are briefly reviewed.

Antibodies to C1q in systemic lupus erythematosus: characteristics and relation to Fc gamma RIIA alleles

Autoantibodies to the collagen-like region of the first complement component (C1qAB) are found in patients with systemic lupus erythematosus (SLE), particularly those with renal disease. In a cohort of 46 SLE patients with diffuse proliferative glomerulonephritis, we found declining C1qAB titers in 77% of treatment responders and in only 38% of treatment non-responders (P < 0.03). To further characterize this autoantibody, we tested 240 SLE patients for the presence of C1qAB. Positive titers were found in 44% of patients with renal disease and 18% of patients without renal disease (chi2 P < 0.0003). Analysis of IgG subclass revealed IgG2 C1qAB alone in 34%, IgG1 C1qAB alone in 20%, and both IgG1 and IgG2 in 46% of patients. Fewer than 10% of patients had measurable titers of IgG3 or IgG4 C1qAB. The pathogenic role of these IgG2-skewed C1qAB may relate to impaired immune complex clearance by the mononuclear phagocyte system: IgG2 antibodies are efficiently recognized by only one IgG receptor, the H131 allele of Fc gamma RIIa (Fc gamma RIIa-H131). In contrast, Fc gamma RIIa-R131, which is characterized by minimal IgG2 binding, has recently been associated with lupus nephritis. In our C1qAB positive patients, the presence of Fc gamma RIIA-R131 was associated with an increased risk for renal disease. Autoantibodies to C1q may have pathogenic significance in SLE patients with genetic defects in the ability to clear IgG2 containing immune complexes.

Immunotactoid glomerulopathy: report of a case

We report a 51-year-old man diagnosed as having immunotactoid glomerulopathy (IT) who achieved partial remission after approximately 1 year of a low-dose prednisolone regimen. On admission, he was noted to show proteinuria, hypoproteinemia, and hypocomplementemia. On electron microscopy of the renal biopsy specimen, the mesangial and subendothelial areas were expanded because of the electron-dense deposits, which were represented by mostly straight and nonbranching hollow microtubule structures. The microtubular width was on average 22.0 nm. Clinical and histological findings did not support the diagnosis of amyloidosis, cryoglobulinemic glomerulonephritis, systemic lupus erythematosus, or paraproteinemias. Under treatment with oral prednisolone, 4 months later, the patient's serum albumin level increased from its lowest level of 2.3 to 3.6 g/dL, and CH50 from the lowest level of less than 6.3 to 32.4 U/mL. A 24-hour collection of urine showed that the protein had decreased from its highest level of 3.9 g to 2.0 g. This case suggests the effectiveness of long-term, low-dose prednisolone therapy for IT.

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.

IgG subclasses in patients with membranoproliferative glomerulonephritis, membranous nephropathy, and lupus nephritis

Primary glomerulopathy can be classified into seven essential patterns based on histopathological studies. The pathogenesis of membranoproliferative glomerulonephritis (MPGN), and membranous nephropathy (MN), which show glomerular IgG deposition and induce mainly nephrotic syndrome, is not known. To clarify the role of IgG subclass in glomerulonephritis, we compared serum concentrations of IgG subclasses, the ratio of serum IgG subclasses to total IgG (%IgG subclass), and glomerular deposition of IgG subclasses between 7 MPGN patients, 21 MN patients, and 9 lupus nephritis (LN) patients. Serum IgG subclasses and %IgG in all groups were almost within normal range based on the values in Japanese healthy adults. In the MPGN and MN groups, the IgG1 concentration was significant lower than that of the LN group (P < 0.001, P < 0.0001, respectively). The IgG2 concentration in the MPGN group decreased significantly compared with that in the LN group (P < 0.05). The %IgG2 of the LN group decreased significantly compared with that of the MN group (P < 0.05). The %IgG3 of the MPGN group was significantly higher that that of the MN group (P < 0.05). The glomerular immunofluorescent intensity of IgG1 and IgG2 were significantly stronger in the LN group than in the MPGN and MN groups (IgG1, P < 0.001, P < 0.01, respectively; IgG2, P < 0.0001, P < 0.0001, respectively). IgG3 in the MPGN and LN groups deposited significantly compared with that in the MN group (P < 0.0001, P < 0.01, respectively). The intensity of IgG4 in the MN group showed a significant difference compared with that in the MPGN and LN groups (P < 0.0001, P < 0.01, respectively). IgG3 is an important factor in the pathogenesis of primary MPGN, while IgG4 relates to glomerular IgG deposition in MN.

Fibrillary glomerulonephritis related to serum fibrillar immunoglobulin-fibronectin complexes

Fibrillary glomerulonephritis is a disease of uncertain origin and pathogenesis characterized by nonamyloidotic fibrils in glomeruli. We report immunohistological, immunochemical, and biochemical studies of a serum fibrillar cryoprecipitate obtained from a patient with fibrillary glomerulonephritis, that formed on prolonged storage at 4 degrees C. By Western blot and amino acid sequence analysis, the cryoprecipitated fibril components consisted of immunoglobulins, heavy chains gamma and mu, light chains kappa and lambda, and fibronectin, similar to the proteins identified by immunofluorescence and immunoelectron microscopy in the glomerular fibrils. These findings support the hypothesis that serum precursors may be the source of the fibrillar deposits and suggest a role for immunoglobulin-fibronectin complexes in the pathogenesis of fibrillary glomerulonephritis.

Familial glomerulopathy with giant fibrillar (fibronectin-positive) deposits: 15-year follow-up in a large kindred

A 15-year clinical follow-up is reported for a familial glomerulopathy characterized on light microscopy by the glomerular deposition of giant fibrillary deposits (Virchows Arch A Pathol Anat Histol 388:313-326, 1980). On electron microscopy, the deposits consist of randomly oriented fibrils (12 to 16 nm in width and 120 to 170 nm in length). These deposits show positive immunoreactivity for fibronectin. One hundred fifty-seven of 197 family members within five generations were investigated. The disease is characterized by the occurrence of albuminuria in the third to fourth decades of life and slow progression to end-stage renal disease over a period of 15 to 20 years with the occurrence of generalized distal tubular acidosis (renal tubular acidosis type IV), hypertension, and the nephrotic syndrome. The frequent occurrence of otherwise unexplained microalbuminuria in young individuals of generations IV and V could be indicative of incipient glomerular disease. In one affected male individual and in his unaffected sister, renal cell carcinoma was diagnosed, raising the possibility that this familial glomerulopathy might be associated with an increased risk to develop renal cell cancer by direct or indirect (associated genetic predisposition) mechanisms. The disease relapsed in one renal transplant, raising the possibility of the presence of a transferable factor that could be part of the deposited fibrillar material or, alternatively, interfere with the glomerular handling of the deposited material.

The primary glomerulopathies

Disorders of glomerular structure and function are encountered frequently in clinical medicine. Many arise as part of a well-defined multisystem or multi-organ disease process, while in others the clinical and laboratory manifestations are consequent to the sole or predominant involvement of glomeruli. The latter are known as the primary glomerulopathies. These disorders can evoke a variety of clinical syndromes, including acute glomerulonephritis, rapidly progressive glomerulo-nephritis, nephrotic syndrome, "symptomless" hematuria and/or proteinuria, and chronic glomerulonephritis. The identification of underlying morphology, through the application of renal biopsy techniques, can provide useful information for both prognosis and treatment. Pathogenic mechanisms involved in the primary glomerulopathies are varied, but immunologic perturbations underlie many disease entities. This article describes the clinical features, pathology, natural history, and treatment of the main categories of primary glomerulonephritis, with emphasis on recent developments and practical aspects of diagnosis and management.

Immunotactoid glomerulopathy with unusually thick extracellular microtubules and nodular glomerulosclerosis in a diabetic patient

It has recently been suggested that immunotactoid glomerulopathy be separated from much more common fibrillary glomerulonephritis by ultrastructural features of highly organized immune deposits containing tubules of more than 30 nm in diameter. We report and discuss the results of a light, immunofluorescence and electron microscopic study of a needle renal biopsy from a 75-year-old, non-insulin dependant diabetic female presented with nephrotic syndrome, hypertension and a progressive renal failure. A unique coexistence of nodular glomerulosclerosis, as traditionally ascribed to diabetes with a peculiar type of immunotactoid glomerulopathy was confirmed by the exclusion of amyloidosis, monoclonal gammopathies, systemic autoimmune diseases and cryoglobulinemia. Mesangial, scattered subepithelial and segmentally prominent subendothelial immune deposits were found highly organized in mostly parallel arrays of 40 to 91 nm thick tubules. The average thickness of 67 nm exceeds the average diameter of tubules in all other 11 published cases of immunotactoid glomerulopathy to date. By immunofluorescence, predominantly capillary wall, thick, ribbon-like glomerular deposits contained IgG, IgM, kappa and lambda light chains of equal intensity, C3, C4 and fibrin related antigens. Mild to moderate glomerular cell proliferation associated with nodular sclerosis has been assumed to be causally related to immunotactoid deposits.

Glomerulopathy associated with predominant fibronectin deposits: a newly recognized hereditary disease

A newly recognized type of familial glomerulopathy observed in patients of both sexes in six families is reported. Proteinuria, often within the nephrotic range, microscopic hematuria, hypertension and a slowly decreasing renal function over several years were common. No underlying systemic diseases were identified. Generally, light microscopy showed enlarged glomeruli with minimal hypercellularity and with extensive deposits in the mesangium and subendothelial space. By electron microscopy, granular deposits with some admixture of fibrils were most common. In one family, the deposits were predominantly fibrillary. Immunoglobulins and complement factors were inconstant or lacking. A main finding was a strong immune reactivity to fibronectin, corresponding to the distribution of the deposits. In one patient, the deposits recurred in a renal transplant. There was no indication of systemic deposition. Abnormalities in the metabolism of circulating fibronectin may play a pathogenetic role in this disease of probably autosomal dominant inheritance.

Familial glomerulonephritis characterized by massive deposits of fibronectin

In recent years more than 150 cases of glomerulonephritis characterized by deposits of irregularly arranged fibrils have been documented. In the majority of these cases immunoglobulins and complement are the prime constituents of these deposits. We recently made a diagnosis of fibrillary glomerulonephritis without immunoglobulin deposition in two members of a family, a father and a son. In the father, proteinuria was first discovered 18 years ago. In 1985 he was referred to our outpatient clinic because of hypertension and increasing proteinuria. From that time onward he was regularly seen for blood pressure control. Nephrotic-range proteinuria persisted, without hardly any evidence of deterioration of renal function. Renal biopsies were performed in 1985 and 1993. His son underwent a renal biopsy in 1993 because of moderate proteinuria. The biopsies of both patients disclosed a distinct form of fibrillary glomerulonephritis that was characterized by massive deposits of a homogeneous, eosinophilic material in the mesangial and subendothelial areas. Staining for amyloid was negative. Immunofluorescence revealed that the biopsy specimens only stained faintly for immunoglobulins, complement factors C1q and C3, the extracellular matrix proteins, collagen IV, and laminin. However, they strongly stained for fibronectin. Using monoclonal antibodies specific for cell-derived fibronectin (IST-9) and plasma- and cell-derived fibronectin (IST-4), in the biopsy of the son we demonstrated that the fibronectin deposited in the glomeruli was mainly derived from the plasma, and to a lesser extent from resident glomerular cells. In addition, a moderate staining for amyloid P and vitronectin also was present. No or minor enhanced staining for collagen I, III, or V, heparan sulfate proteoglycan or its glycosaminoglycan side chains, tenascin, or thrombospondin could be observed. By electron microscopy the deposits in the mesangium and the subendothelial spaces appeared focally to be composed of irregularly arranged fibrils or microtubules 10 to 12 nm in diameter. Fibrillary glomerulonephritis with massive deposits of fibronectin represents a rare form of familial glomerulonephritis. In our patients the glomerulonephritis has an indolent course with hardly any deterioration of renal function.

Localization of extracellular matrix components in congenital nephrotic syndromes

While renal tissue from one fetus and a newborn with congenital nephrotic syndrome, Finnish type (FCNS), showed a normal basement membrane (BM) localization and composition, in another type of congenital nephrotic syndrome, diffuse mesangial sclerosis (DMS), most glomeruli demonstrated a completely disorganized matrix. In the latter, hyalinized glomerular segments were composed of irregular deposits of interstitial collagens I, III, V, and extensive deposits of heparin sulphate proteoglycan (HSPG), while collagen IV and laminin were completely absent in those areas. Apart from these sclerosed glomerular areas, normal capillarly loops revealed a matrix composition that was comparable to normal glomeruli. The additional immunolocalization of various extracellular matrix components during the development of normal human glomeruli revealed some significant age-dependent changes both in the localization of interstitial collagens and BM components: interstitial collagens I and III disappeared after the first S-shaped indentations appeared, while the interstitial collagen V remained along the glomerular BM and within the mesangium. The BM components showed no significant qualitative changes, but quantitative changes, with a post-natal relative decrease in the collagen IV and laminin content when compared with the level of BM-associated HSPG. Our results provide circumstantial evidence that the composition of the extracellular matrix (and in particular of the BM) shows age-dependent quantitative changes which may be associated with functional adaptation processes of the developing kidney. The observed matrix composition in the two different congenital nephrotic syndromes suggests various pathomechanisms which may be located either in the molecular structure of the negatively charged molecules (e.g. abnormal sulphatation of HSPG in FCNS) or in the dysregulated synthesis of various matrix components (DMS).

A practical approach to the diagnosis of renal disease by biopsy

The pathologist has an important role in the diagnosis and monitoring of renal disease. However, for optimal useful information to be derived from renal biopsy specimens, certain guidelines must be adhered to and these are enunciated here. The 3 avenues of observation of renal biopsies viz. light microscopy, immunofluorescence and electron microscopy, all have important roles to play and give differing data which informs the diagnosis for the renal biopsy report. The relative emphasis on each of these modalities of investigation will vary depending upon the situation in which the renal biopsy is performed. The methods used here have been shown to be effective in practice over a period of 20 yrs. Although there may be variations in methodology from centre to centre, the general background aims and principles remain the same. The emphasis in this paper has been on common practical aspects of renal biopsies. Much of the practical information concerning renal biopsies, which is brought together here, is otherwise scattered and not readily available. The aim of this article is to allow the reader to understand the rationale for the steps that are involved in renal biopsy diagnosis.

Recurrent diseases in the kidney transplant

Virtually all diseases affecting the native kidney recur in the kidney transplant with the exception of Alport syndrome, polycystic kidney disease, hypertension, chronic pyelonephritis, and chronic interstitial nephritis. Fortunately, in the majority of patients, recurrence of the original disease has minimal clinical impact, with only approximately 5% of all graft loss occurring as a result of recurrent disease. The primary renal diseases that commonly recur include membranoproliferative glomerulonephritis type II, IgA nephropathy, and focal and segmental glomerular sclerosis. The most common systemic disease that recurs is diabetic nephropathy. Living-related transplantation should be used with caution in patients with the hemolytic uremic syndrome, recurrent focal and segmental glomerular sclerosis, and membraneous glomerulonephritis. Fabry disease and primary hyperoxaluria type I are no longer absolute contraindications to kidney transplantation.

The fibrillary glomerulopathies

Fibrillary glomerulopathy is a category of glomerular disease that is defined by the ultrastructural feature of organized deposits of extracellular, nonbranching, microfibrils. The best-known disease in this category is amyloidosis, but cryoglobulinemia, light chain deposition disease, systemic lupus erythematosus, immunotactoid glomerulopathy, and diabetic fibrillosis may have similar ultrastructural findings and comprise the differential diagnosis of the fibrillary glomerulopathies. Because they have disease-specific therapeutic and prognostic implications, differentiating among these entities is important for nephrologists and nephropathologists. To aid the physician, we will review the fibrillary glomerulopathies using an algorithm based on morphology, clinical features, and serologic assessment. We believe this approach will prove to be practical and useful to the practicing nephrologist.

IgG subclass deposits in glomeruli of lupus and nonlupus membranous nephropathies

Membranous nephropathy (MN) accounts for approximately 10% of all renal lesions of systemic lupus erythematosus (SLE). These membranous lesions often have a clinical presentation similar to that of idiopathic MN and may present before SLE is apparent clinically. However, unlike proliferative lesions of lupus nephritis (LN), membranous LN often does not show a "full-house" pattern of glomerular immunoglobulin and complement (C) deposits by immunofluorescence (IF); only nine of 14 such lesions that we examined stained for all of the following: IgG, IgA, IgM, C3, and C1q. Iskandar et al reported in 1992 that most cases of diffuse proliferative LN showed IgG3 as the major IgG subclass present in glomerular deposits; by contrast, IgG4 predominated in six of seven cases of MN of unspecified etiology. If IgG subclass deposition is similar in membranous and proliferative lesions of LN, then IF staining for IgG3 and IgG4 may be helpful in distinguishing lupus from nonlupus lesions in patients with MN who are lacking a firm diagnosis of SLE. We therefore stained cryostat sections of renal biopsies from 14 patients with SLE and MN (without a proliferative component; World Health Organization [WHO] classes Va and Vb) and 28 non-SLE patients with MN for IgG subclasses by direct IF; the observer was blind to the diagnosis for each case until all were read. The intensity of glomerular staining was graded on a 0 to 4+ scale with increments of 0.5+.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary-renal syndrome in a patient with fibrillary glomerulonephritis

A patient presented with a rapid deterioration in renal function requiring dialysis. Renal biopsy demonstrated fibrillary glomerulonephritis. The patient was treated with steroids and cyclophosphamide and recovered sufficient renal function to discontinue dialysis. However, as immunosuppressive therapy was withdrawn, renal function worsened and the patient developed pulmonary hemorrhage and respiratory distress. Immunosuppressive therapy was reinstituted. During treatment the patient's renal function improved and pulmonary manifestations resolved. This case is further evidence that fibrillary glomerulonephritis can present as a pulmonary-renal syndrome and can respond to aggressive treatment with immunosuppressive agents.

Fibrillary glomerulonephritis without immunoglobulin deposits in the kidney

Three patients are presented, who by electron microscopy, showed prominent fibrillary deposits in the glomeruli, and in two, also around the tubules. By immunohistology these two cases had no immunoglobulins in either glomeruli or around the tubules. In the third case, which probably represents a slightly different form of the disease, minor deposits of IgM were found in the glomeruli, while fibrillary deposits were extensive and widespread. It is suggested that precursors of fibrillary deposits may not be the same in all cases.

Morphologic and clinical features of fibrillary glomerulonephritis versus immunotactoid glomerulopathy

Renal diseases characterized by Congo red-negative extracellular fibrillary deposits, either organized arrays of larger, microtubular fibrils (immunotactoid glomerulopathy [IT]) or smaller, randomly organized fibrils (fibrillary glomerulonephritis), have been recognized recently. The clinical significance, if any, of the distinction of these patterns has not been determined. On review of all renal biopsy specimens evaluated in a private referral renal pathology laboratory over the last 11 years, 26 cases with fibrillary glomerulonephritis pattern were identified and compared with our six most recent cases with the IT pattern. The fibrillary glomerulonephritis patients, 17 women and nine men, had an average age of 50 +/- 2 years and contributed 1% of the renal biopsy specimens examined. All patients had marked proteinuria and 16 had microscopic hematuria. Follow-up at 23 +/- 5 months in 25 of these patients revealed end-stage renal disease in 11 patients (44%) and one death due to renal failure. End-stage renal disease developed an average of 10 +/- 5 months after biopsy. One patient developed multiple myeloma. Twenty-four renal biopsy specimens showed proliferation, with crescents in seven. Immunofluorescence showed moderate to intense staining for immunoglobulin G and weaker staining for C3, in a predominantly mesangial pattern, with weaker glomerular basement membrane (GBM) staining, corresponding to electron microscopic deposit localization. In four cases, linear GBM staining by immunofluorescence corresponded to extensive subendothelial or transmembranous deposits. The average fibril diameter was 14.0 +/- 0.5 nm (range, 10.4 to 18.4 nm). Immunotactoid glomerulopathy patients (three women and three men) were significantly older, 62 +/- 2 years (P < 0.025). All had marked proteinuria, with microscopic hematuria in two patients. Associated hematopoietic diseases were present in four patients, with monoclonal proteins and/or abnormal plasma cell proliferation in three. One patient died of nonrenal causes. The remaining five patients have stable renal function at 20 +/- 5 months. Biopsy specimens showed proliferative (n = 3) or membranous-like (n = 3) patterns. Immunofluorescence showed immunoglobulin G and weaker C3 staining in a granular GBM pattern, with lesser mesangial staining. The microtubular fibril diameter was on average 43.2 +/- 10.3 nm (range, 16.8 to 90.0 nm). Thus, fibrillary glomerulonephritis and IT can be separated based on ultrastructurally distinct features. Patients with fibrillary glomerulonephritis are less likely than those with IT to have associated hematopoietic disease and also have poorer renal survival. We propose that classification based on these morphologic differences appears to have clinical significance.