Monoclonal gammopathy of renal significance: Diagnostic workup

The clinical spectrum of diseases associated with monoclonal gammopathies is wide and they are most commonly the consequence of renal deposition of monoclonal immunoglobulin or its components. The differential diagnosis is difficult and renal biopsy is essential. To distinguish many of these pathologies is necessary to use techniques that are not always available, even in tertiary central hospitals. This review will discuss the clinical presentation, pathologic features, treatment, prognosis and common diagnostic difficulties of these entities.

Paraprotein-Related Kidney Disease: Glomerular Diseases Associated with Paraproteinemias

Paraproteins are monoclonal Igs that accumulate in blood as a result of abnormal excess production. These circulating proteins cause a diversity of kidney disorders that are increasingly being comanaged by nephrologists. In this review, we discuss paraprotein-related diseases that affect the glomerulus. We provide a broad overview of diseases characterized by nonorganized deposits, such as monoclonal Ig deposition disease (MIDD), proliferative GN with monoclonal Ig deposits (PGNMID), and C3 glomerulopathy, as well as those characterized by organized deposits, such as amyloidosis, immunotactoid glomerulopathy, fibrillary GN, and cryoglobulinemic GN, and rarer disorders, such as monoclonal crystalline glomerulopathies, paraprotein-related thrombotic microangiopathies, and membranous-like glomerulopathy with masked IgGκ deposits. This review will provide the nephrologist with an up to date understanding of these entities and highlight the areas of deficit in evidence and future lines of research.

Spectrum of manifestations of monoclonal gammopathy-associated renal lesions

PURPOSE OF REVIEW

Monoclonal gammopathies result from an overt malignant process, such as multiple myeloma, or a premalignant process, such as monoclonal gammopathy of undetermined significance. The kidney is often affected in the setting of a monoclonal gammopathy. The term 'monoclonal gammopathy of renal significance (MGRS)' was recently introduced to draw attention to renal diseases related to the monoclonal gammopathy. In this review, we define the pathology of these monoclonal gammopathy-associated kidney diseases.

RECENT FINDINGS

Renal disease can be caused by deposition of the monoclonal immunoglobulin (direct mechanism) or by activation of the alternative pathway of complement by the monoclonal immunoglobulin (indirect mechanism). The deposition of monoclonal immunoglobulin can affect the glomeruli, tubules, and the interstitium and vessels. The glomerular diseases include proliferative glomerulonephritis with monoclonal immunoglobulin deposits, immunotactoid glomerulopathy, and, less commonly, fibrillary glomerulonephritis. Tubular lesions associated with monoclonal immunoglobulin include cast nephropathy and light-chain proximal tubulopathy. Lesions involving the glomeruli, tubules, interstitium or vessels include amyloidosis and monoclonal immunoglobulin deposition diseases. Rarely, monoclonal immunoglobulin may also cause C3 glomerulopathy or atypical hemolytic uremic syndrome by interfering with the regulation of the alternative pathway of complement.

SUMMARY

Monoclonal gammopathy are associated with a variety of kidney diseases. The monoclonal gammopathy-associated renal diseases are distinct in their pathogenesis, kidney biopsy findings, clinical presentation, progression, prognosis, and treatment. The term monoclonal gammopathy of renal significance helps highlight patients who have renal disease secondary to monoclonal immunoglobulin secreted by a premalignant or malignant clone, but is not a disease or diagnosis in itself.

A case report of unusually long lag time between immunotactoid glomerulopathy (itg) diagnosis and diffuse large B-cell lymphoma (DLBCL) development

Background

Immunotactoid glomerulopathy (ITG) is a rare cause of proteinuria characterized by organized microtubular deposits in the glomerulus. ITG has been associated with underlying lymphoproliferative disorders and any renal impairment may be reversible with treatment of the concomitant hematologic malignancy. This case is the first reported in literature where diffuse large B cell lymphoma developed two years following the initial ITG diagnosis.

Case presentation

A 55-year-old woman with a history of well-controlled diabetes mellitus and thalassemia trait presented with proteinuria (830 mg/day) in 2010. Initially, she was managed with renin-angiotensin-aldosterone-system blockade. In 2012, the proteinuria worsened (4.3 g/day) and a renal biopsy showed immunotactoid glomerulopathy (Fig. 1). Despite extensive work up, no lymphoproliferative disorder was initially found. In January 2014, the patient presented with a soft-palate mass found on biopsy to be diffuse large B-cell lymphoma. She received 6 cycles of R-CHOP, 4 cycles of high dose methotrexate chemotherapy for CNS prophylaxis and 30 Gy of Intensity Modulated Radiation Therapy. Follow-up revealed complete remission of diffuse large B-cell lymphoma and resolution of proteinuria from the ITG.

Conclusion

As we recognize that patients with ITG may develop hematopoietic neoplasms, close long-term monitoring is important. Moreover, treatment of the lymphoproliferative disorder can allow for complete remission of ITG.

Bridging the Divide: An Onco-Nephrologic Approach to the Monoclonal Gammopathies of Renal Significance

The monoclonal gammopathies of renal significance (MGRS) are a group of disorders characterized by monoclonal Ig deposition in the kidney, but are not associated with systemic lymphoma or overt multiple myeloma. The prevailing hypothesis is that the pathogenic paraproteins in MGRS are produced by underlying B cell or plasma cell clones. However, in the MGRS literature, the yield of detecting a clone has been variable, and progression to ESRD is common. Here, we present an "onco-nephrologic" approach to the MGRS disorders by highlighting recent advances in lymphoma and multiple myeloma that can be used in the evaluation and management of these patients.

IgG Subclass Staining in Routine Renal Biopsy Material

Immunofluorescence staining plays a vital role in nephropathology, but the panel of antibodies used has not changed for decades. Further classification of immunoglobulin (Ig)G-containing immune-type deposits with IgG subclass staining (IgG1, IgG2, IgG3, and IgG4) has been shown to be of diagnostic utility in glomerular diseases, but their value in the evaluation of renal biopsies has not been addressed systematically in large renal biopsy material. Between January 2007 and June 2014, using direct immunofluorescence, we stained every renal biopsy for the IgG subclasses if there was moderate to prominent glomerular IgG staining and/or IgG-predominant or IgG-codominant glomerular staining. The total number of biopsies stained was 1084, which included 367 cases of membranous glomerulonephritis, 307 cases of lupus nephritis, 74 cases of fibrillary glomerulonephritis, 53 cases of proliferative glomerulonephritis with monoclonal IgG deposits, and 25 cases of antiglomerular basement membrane disease, among others. We found that monoclonality of IgG deposits cannot always be reliably determined on the basis of kappa and lambda light chain staining alone, particularly if concomitant (frequently nonspecific) IgM staining is present. In IgG heavy and heavy and light chain deposition disease (3 cases), subclass staining is very helpful, and in proliferative glomerulonephritis with monoclonal IgG deposits subclass staining is necessary. IgG subclass staining is useful in differentiating primary from secondary membranous glomerulonephritis. In proliferative glomerulonephritis with polyclonal IgG deposition, IgG1 dominance/codominance with concomitant IgG3 and IgG2 but weak or absent IgG4 staining favors an underlying autoimmune disease. IgG subclass staining is a very useful diagnostic method in a selected cohort of renal biopsies, particularly in biopsies with glomerulonephritis with monoclonal IgG deposits.

A Patient with Abnormal Kidney Function and a Monoclonal Light Chain in the Urine

Monoclonal gammopathy is increasingly recognized as a cause of kidney injury. These renal conditions behave differently than ones without monoclonal gammopathy and require specific treatment. To avoid misdiagnosis, testing for paraprotein should be performed in addition to vasculitis and autoimmune diseases serologies in adults with unexplained AKI or proteinuria. Because the prevalence of monoclonal gammopathy is much more common than glomerular diseases, the nephrotoxicity of the monoclonal protein must be confirmed before cytotoxic therapy is initiated. This can only be done by a kidney biopsy. After a monoclonal gammopathy of renal significant is verified, the evaluation should then focus on the identification of the pathologic clone, because therapy is clone specific. We present this patient to illustrate the clinical presentation of a patient with renal dysfunction and a monoclonal gammopathy. This patient is also used to discuss the diagnostic process in detail when monoclonal gammopathy-associated renal disease is suspected.

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.

Haematuria as a risk factor for chronic kidney disease progression in glomerular diseases: A review

Haematuria has long been considered to be a benign condition associated with glomerular diseases. However, new evidences suggest that haematuria has a pathogenic role in promoting kidney disease progression. An increased risk for end-stage renal disease has been reported in adolescents and young adults with persistent microscopic haematuria. A persistent impairment of renal function has been also reported following macroscopic haematuria-associated acute kidney injury in immunoglobulin A nephropathy. Haematuria-induced renal damage has been related to oxidant, cytotoxic and inflammatory effects induced by haemoglobin or haem released from red blood cells. The pathophysiological origin of haematuria may be due to a more fragile and easily ruptured glomerular filtration barrier, as reported in several glomerular diseases. In this review we describe a number of the key issues associated with the epidemiology and pathogenesis of haematuria-associated diseases, provide an update of recent knowledge on the role of haematuria on renal function outcome and discuss specific therapeutic approaches in this setting. KEY SUMMARY POINTS: 1. Glomerular haematuria is a common observation in a number of renal diseases that may lead to persistent renal injury. 2. Haematuria in children differs from that in adults in specific aspects, particularly in the frequency of glomerular diseases and renal disease outcome. 3. Regular follow-up of renal function in children with isolated microhaematuria may be recommended.

[Renal involvement during type 1 cryoglobulinemia]

Cryoglobulins are circulating immunoglobulins that precipitate with cold temperature and dissolve with rewarming. Type 1 cryoglobulinemia is composed of a single monoclonal immunoglobulin and is associated with renal involvement in up to 40% of cases. Type 1 cryoglobulinemia is related to an underlying B-cell haematological malignancy in 60% of patients. In the remaining cases, in the absence of criteria for malignancy, the diagnosis of monoclonal gammopathy of renal significance should be established. The clinical and biological setting and histological features of type 1 cryoglobulinemia are globally similar to those of mixed cryoglobulinemia. In case of haematological malignancy, the treatment is guided by the nature of the underlying disease, and aims at inducing haematological remission, which is necessary for the renal response. The management of monoclonal gammopathy of renal significance has been clarified by an international consensus group and is based on the nature of the underlying clone. In case of monoclonal cryoglobulinemia associated with a plasma-cell clone (IgG or IgA), the treatment is based on the combination of bortezomib, cyclophosphamide and dexamethasone. In case of IgM monoclonal cryoglobulinemia, the treatment is similar to that of Waldenström macroglobulinemia, and is based on rituximab. The clinical course of renal monoclonal cryoglobulinemia is intimately associated with the haematological response, and is usually favourable.

Proliferative Glomerulonephritis With Monoclonal IgG1κ Deposits in a Hepatitis C Virus-Positive Patient

Hepatitis C virus infection is associated with several glomerular diseases, most commonly cryoglobulinemic glomerulonephritis, which is typically secondary to type II mixed cryoglobulinemia. We present a patient with hepatitis C virus infection and cryoglobulinemic glomerulonephritis secondary to type I (monoclonal) cryoglobulinemia that is likely related to a concurrent hepatitis C virus infection-associated lymphoproliferative disorder. We list the differential diagnosis of cryoglobulinemic glomerulonephritis. Additionally, the case draws attention to the possibility that, rarely, even clinically undetectable "occult" B-cell lymphoproliferative disorders may result in significant kidney disease.

Hematologic characteristics of proliferative glomerulonephritides with nonorganized monoclonal immunoglobulin deposits

OBJECTIVE

To study the hematologic characteristics of proliferative glomerulonephritides (GNs) from nonorganized glomerular monoclonal immunoglobulin (MIg) deposition (MIPG).

PATIENTS AND METHODS

The pathology database at Mayo Clinic (Rochester, Minnesota) was used to find patients with MIPG who underwent a kidney biopsy between January 1, 2008, and December 31, 2013. Retrospective medical record review was conducted in the identified cohort (N=60).

RESULTS

The median patient age was 56 years (interquartile range, 47-62 years) and the estimated glomerular filtration rate was 36 mL/min/1.73 m(2) (interquartile range, 22-52 mL/min/1.73 m(2)). Most patients had IgG MIg deposits (90%; 54 of 60) and a membranoproliferative pattern (48%; 29 of 60). A circulating nephropathic MIg was detected by serum immunofixation (SIFE(+)) in 20% (12 of 59) and by abnormal serum free light chain ratio (sFLCR(+)) in 21% (12 of 56). The subsets of SIFE(+) and sFLCR(+) incompletely overlapped. The nephropathic clone was found by bone marrow testing (BM(+)) in 25% (10 of 40; 6 plasma cell clones [5 IgG; 1 IgA], 3 chronic lymphocytic leukemia [all IgG], and 1 lymphoplasmacytic clone [IgM]). The clone detection rate was significantly higher in patients with SIFE(+) (P<.001) and in those with SIFE(+) and/or sFLCR(+) (P<.001). Patients with SIFE(+) and BM(+) frequently had IgG1-restricted MIg deposits on renal biopsy immunofluorescence (P=.005). Most BM(+) patients required flow cytometry and immunohistochemical analysis of the marrow specimen for accurate diagnosis.

CONCLUSION

Undetectable circulating nephropathic MIg and pathologic clones characterize most MIPG. Immunoglobulin isotype may predict detectability of MIg and clone by currently available technology. Bone marrow evaluation, including flow cytometry and immunohistochemical analysis, should be performed for SIFE(+) and/or sFLCR(+). More sensitive clone-identifying techniques in the marrow and extramedullary tissue are needed when SIFE and sFLCR test negative.

Granulomatous interstitial nephritis secondary to chronic lymphocytic leukemia/small lymphocytic lymphoma

Granulomatous interstitial nephritis (GIN) is an uncommon pathologic lesion encountered in 0.5% to 5.9% of renal biopsies. Drugs, sarcoidosis, and infections are responsible for most cases of GIN. Malignancy is not an established cause of GIN. Here, we report a series of 5 patients with GIN secondary to chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Patients were mostly elderly white males with an established history of CLL/SLL who presented with severe renal impairment (median peak serum creatinine, 7.3 mg/dL), leukocyturia, and mild proteinuria. One had nephromegaly. In 2 patients, the development and relapse of renal insufficiency closely paralleled the level of lymphocytosis. Kidney biopsy in all patients showed GIN concomitant with CLL/SLL leukemic interstitial infiltration. Granulomas were nonnecrotizing and epithelioid and were associated with giant cells. One biopsy showed granulomatous arteritis. One patient had a granulomatous reaction in lymph nodes and skin. Steroids with/without CLL/SLL-directed chemotherapy led to partial improvement of kidney function in all patients except 1 who had advanced cortical scarring on biopsy. In conclusion, we report an association between CLL/SLL and GIN. Patients typically present with severe renal failure due to both GIN and leukemic interstitial infiltration, which tends to respond to steroids with/without CLL/SLL-directed chemotherapy. The pathogenesis of GIN in this clinical setting is unknown but may represent a local hypersensitivity reaction to the CLL/SLL tumor cells.

Renal involvement in monoclonal gammopathy

Monoclonal gammopathy is produced by neoplastic or non-neoplastic expansion of a clone of plasma cells or B lymphocytes. Monoclonal gammopathy of unknown significance is characterized by low levels of the monoclonal protein and a relatively small population of clonal lymphocytes or plasma cells in the bone marrow. In these cases, the patient is asymptomatic with no evidence of overt myeloma or lymphoma. The abnormal serum protein may be present as a complete immunoglobulin molecule or may consist of ≥1 of its components such as light chains or heavy chains. These proteins may cause a variety of diseases in various tissues and organs, of which the kidney appears to be the most vulnerable. Renal involvement in monoclonal gammopathy may occur as part of a generalized disease such as amyloidosis, immunoglobulin deposition disease, and cryoglobulinemia. In addition, there may be evidence of kidney damage by processes which are renal specific. These include light chain proximal tubulopathy, light chain cast nephropathy, and a variety of glomerulopathies encompassing a wide spectrum of disease patterns.

Diagnosis of monoclonal gammopathy of renal significance

Monoclonal gammopathy of renal significance (MGRS) regroups all renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a nonmalignant B-cell clone. By definition, patients with MGRS do not meet the criteria for overt multiple myeloma/B-cell proliferation, and the hematologic disorder is generally consistent with monoclonal gammopathy of undetermined significance (MGUS). However, MGRS is associated with high morbidity due to the severity of renal and sometimes systemic lesions induced by the MIg. Early recognition is crucial, as suppression of MIg secretion by chemotherapy often improves outcomes. The spectrum of renal diseases in MGRS is wide, including old entities such as AL amyloidosis and newly described lesions, particularly proliferative glomerulonephritis with monoclonal Ig deposits and C3 glomerulopathy with monoclonal gammopathy. Kidney biopsy is indicated in most cases to determine the exact lesion associated with MGRS and evaluate its severity. Diagnosis requires integration of morphologic alterations by light microscopy, immunofluorescence (IF), electron microscopy, and in some cases by IF staining for Ig isotypes, immunoelectron microscopy, and proteomic analysis. Complete hematologic workup with serum and urine protein electrophoresis, immunofixation, and serum-free light-chain assay is required. This review addresses the pathologic and clinical features of MGRS lesions, indications of renal biopsy, and a proposed algorithm for the hematologic workup.

[Minimal-change glomerulonephritis in chronic lymphocytic leukemia: A clinical case]

Chronic lymphocytic leukemia (CLL) in association with glomerulonephritis (GN) and renal failure is a serious problem in terms of therapy. The paper reports a clinical case of a 64-year-old female patient with Binet stage C CLL accompanied by minimal-change GN complicated by nephrotic syndrome and the development of acute renal failure. GN was diagnosed on the basis of electron microscopic studies of renal biopsy specimens. It was treated with rituximab in combination with bendamustine. The former was intravenously injected in a dose of 375 mg/m2 on day 0 of the cycle; the latter was given in a dose of 70 mg/m2 within the first 2 days; the cycle was repeated 28 days after initiation of the previous cycle. Five cycles could result in complete CLL remission (the follow-up duration was 20 months); nephrotic syndrome was completely abolished and kidney function recovered.

Rituximab-cyclophosphamide-dexamethasone is highly effective in patients with monoclonal Ig deposit-related glomerulopathy and indolent non-Hodgkin lymphomas

Indolent non-hodgkin lymphomas (iNHL) are a rare cause of monoclonal immunoglobulin deposits-related glomerulopathy (mIgGN). In patients with iNHL-related mIgGN, whether treatment should include either single or a combination of drug(s) to target the malignant clone and renal inflammation remains elusive. In this retrospective study, we report a cohort of 14 patients with iNHL-related mIgGN (cryoglobulinemic glomerulonephritis [n = 5], membranous nephropathy [n = 3], membranoproliferative glomerulonephritis [n = 3], AL or AL/AH amyloidosis [n = 2], and Light Chain Deposits Disease [n = 1]) and who received a treatment combining rituximab, cyclophosphamide, and dexamethasone (RCD). After a mean follow-up of 18 ± 4 months, nine patients (63%) had complete haematological response. Renal response was observed in 12 of the 14 patients (86%; complete response: n = 9; partial: n = 3). Estimated glomerular filtration rate increased from 47 ± 7 to 63 ± 8 mL/min/1.73 m(2) , and proteinuria decreased from 6.5 ± 0.7 to 1.4 ± 0.8 g/24 hr at one year. Following hematological relapse, renal relapse occurred in two patients suggesting sustained clonal eradication offers the best renal protection. Tolerance of RCD was good and the most frequent adverse event was pneumonia (3/14, 21%). RCD is a promising regimen for patients with iNHL and mIgGN, irrespective of glomerular pathologic pattern. Whether steroids can be avoided or minimized remains to be addressed.

Monoclonal light chain deposits within the stomach manifesting as immunotactoid gastropathy

Immunotactoid deposits are defined by their ultrastructural appearance and are characterized by microtubular or cylindrical structures typically measuring greater than 30 nm in diameter. Although a rare entity, immunotactoid deposition most often manifests as immunotactoid glomerulopathy and is associated with underlying lymphoplasmacytic disorders. Corneal immunotactoid deposition known as immunotactoid keratopathy has also been reported in patients with paraproteinemia. Here, we describe the first reported case of immunotactoid deposition in the stomach. The deposits were composed solely of kappa immunoglobulin light chains without significant lambda light chain or immunoglobulin heavy chain components. The patient displayed no renal signs or symptoms, and additional thorough clinical examination failed to detect any evidence of a paraproteinemia or plasma cell dyscrasia. Thus, the gastric immunotactoid deposits in this case appear to be an isolated finding of light chain deposition, of which the significance and etiology are unclear.

Renal Amyloidosis

Amyloidosis is an uncommon group of diseases in which soluble proteins aggregate and deposit extracellularly in tissue as insoluble fibrils, leading to tissue destruction and progressive organ dysfunction. More than 25 proteins have been identified as amyloid precursor proteins. Amyloid fibrils have a characteristic appearance on ultrastructural examination and generate anomalous colors under polarized light. Amyloidosis can be systemic or localized. The kidney is a prime site for amyloid deposition. Immunofluorescence, immunoperoxidase, and more recently laser microdissection and mass spectrometry are important tools used in the typing of renal amyloidosis.

Diagnosis and treatment of glomerular diseases in elderly patients

Glomerular diseases are common in elderly patients and are a major cause of kidney failure. Most glomerular diseases in the elderly are caused by chronic systemic diseases, including arterial hypertension, diabetes, and atherosclerotic vascular diseases, although acute systemic vasculitis, especially anti-neutrophil-cytoplamic-antibody-mediated vasculitis, and membranous nephropathy related to malignancy, drug toxicity, and idiopathic form also occur often. Complex age-related changes and sensitivity to drug toxicity can render diagnosis and treatment for elderly patients challenging. As the general population is aging and the rate of CKD rising, updating knowledge on managing these patients is critical for care providers. We provide a comprehensive review and update of the diagnosis and treatment of glomerular diseases in the elderly.

Myeloma-related kidney disease

Multiple myeloma is a malignant plasma cell disorder characterized by the overproduction of monoclonal proteins. The kidney is 1 of the major target organs of multiple myeloma. Most often, this is the result of the monoclonal proteins, which can injure the kidney via several mechanisms. In some cases, direct invasion by myeloma cells and/or bone marrow cells can also result in kidney injury. A kidney biopsy can help distinguish the various myeloma-related kidney diseases and aid in the treatment plan.

Urinary prognostic biomarkers and classification of IgA nephropathy by high resolution mass spectrometry coupled with liquid chromatography

IgA nephropathy is the most common cause of primary glomerulonephritis. There are different pathologic biopsy-based scoring systems in use, but there is no consensus among nephrologists yet regarding the best classification method. Our aim was to test urine proteomics as a non-invasive method for classification of IgA nephropathy. This aim was pursued by discovering novel prognostic protein biomarkers in urine, and linking them to pathogenesis of the disease through known signaling and metabolic pathways. 13 urine samples of the patients with biopsy-proven IgA nephropathy were analyzed via two proteomics approaches: nanoflow LC-MS/MS and GeLC-MS/MS. The results of label-free quantification were subjected to multivariate statistical analysis, which could classify patients into two groups, broadly corresponding to the primary and advance stages. The proteome classification correlated well with biopsy-based scoring systems, especially endocapillary hypercellularity score of the Oxford’s classification. Differentially excreted candidate proteins were found as potential prognostic biomarkers: afamin, leucine-rich alpha-2-glycoprotein, ceruloplasmin, alpha-1-microgolbulin, hemopexin, apolipoprotein A-I, complement C3, vitamin D-binding protein, beta-2-microglobulin, and retinol-binding protein 4. Pathway analysis suggested impairment of Extra Cellular Matrix (ECM)-Receptor Interaction pathways as well as activation of complement and coagulation pathway in progression of IgA nephropathy.

How I treat monoclonal gammopathy of renal significance (MGRS)

Recently, the term monoclonal gammopathy of renal significance (MGRS) was introduced to distinguish monoclonal gammopathies that result in the development of kidney disease from those that are benign. By definition, patients with MGRS have B-cell clones that do not meet the definition of multiple myeloma or lymphoma. Nevertheless, these clones produce monoclonal proteins that are capable of injuring the kidney resulting in permanent damage. Except for immunoglobulin light chain amyloidosis with heart involvement in which death can be rapid, treatment of MGRS is often indicated more to preserve kidney function and prevent recurrence after kidney transplantation rather than the prolongation of life. Clinical trials are rare for MGRS-related kidney diseases, except in immunoglobulin light chain amyloidosis. Treatment recommendations are therefore based on the clinical data obtained from treatment of the clonal disorder in its malignant state. The establishment of these treatment recommendations is important until data can be obtained by clinical trials of MGRS-related kidney diseases.

Shotgun-proteomics-based clinical testing for diagnosis and classification of amyloidosis

Shotgun proteomics technology has matured in the research laboratories and is poised to enter clinical laboratories. However, the road to this transition is sprinkled with major technical unknowns such as long-term stability of the platform, reproducibility of the technology and clinical utility over traditional antibody-based platforms. Further, regulatory bodies that oversee the clinical laboratory operations are unfamiliar with this new technology. As a result, diagnostic laboratories have avoided using shotgun proteomics for routine diagnostics. In this perspectives article, we describe the clinical implementation of a shotgun proteomics assay for amyloid subtyping, with a special emphasis on standardizing the platform for better quality control and earning clinical acceptance. This assay is the first shotgun proteomics assay to receive regulatory approval for patient diagnosis. The blueprint of this assay can be utilized to develop novel proteomics assays for detecting numerous other disease pathologies.

Long-term kidney disease outcomes in fibrillary glomerulonephritis: a case series of 27 patients

BACKGROUND

Fibrillary glomerulonephritis (GN) is a rare disorder with poor renal prognosis. Therapeutic strategies, particularly the use of immunosuppressive drugs, are debated.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

27 adults with fibrillary GN referred to 15 nephrology departments in France between 1990 and 2011 were included. All patients were given renin-angiotensin system blockers and 13 received immunosuppressive therapy, including rituximab (7 patients) and cyclophosphamide (3 patients).

OUTCOMES & MEASUREMENTS

Clinical and histologic features of patients and kidney disease outcome. Renal response was defined as a >50% decrease in 24-hour proteinuria with <15% decline in estimated glomerular filtration rate (eGFR).

RESULTS

All patients presented with proteinuria, associated with nephrotic syndrome (41%), hematuria (73%), and hypertension (70%). Baseline median eGFR was 49 mL/min/1.73 m(2). Eight patients had a history of autoimmune disease and none had evidence of hematologic malignancy during follow-up. Light microscopic studies showed mesangial GN (70%), predominant pattern of membranous GN (19%), or membranoproliferative GN (11%). By immunofluorescence, immunoglobulin G (IgG) deposits (IgG4, 15/15; IgG1, 9/15) were polyclonal in 25 cases. Serum IgG subclass distribution was normal in the 6 patients tested. After a median 46-month follow-up, renal response occurred in 6 of 13 patients who received immunosuppressive therapy with rituximab (5 patients) or cyclophosphamide (1 patient). Of these, 5 had a mesangial or membranous light microscopic pattern, and median eGFR before therapy was 76 mL/min/1.73 m(2). In contrast, chronic kidney disease progressed in 12 of 14 patients who were not given immunosuppressive therapy, 10 of whom reached end-stage renal disease.

LIMITATIONS

Number of patients, retrospective study, use of multiple immunosuppressive regimens.

CONCLUSIONS

The therapeutic approach in fibrillary GN remains challenging. The place of immunosuppressive therapy, particularly anti-B-cell agents, needs to be assessed in larger collaborative studies.