Negative Staining for COL4A5 Correlates With Worse Prognosis and More Severe Ultrastructural Alterations in Males With Alport Syndrome

Introduction

Alport syndrome (AS) is a genetic disorder characterized by progressive hematuric nephropathy with or without sensorineural hearing loss and ocular lesions. Previous studies on AS included mostly children.

Methods

To determine the prognostic value of loss of staining for collagen type IV alpha 5 (COL4A5) and its relationship with the ultrastructural glomerular basement membrane alterations, we performed direct immunofluorescence using a mixture of fluorescein isothiocyanate-conjugated and Texas-red conjugated antibodies against COL4A5 and COL4A2, respectively, on renal biopsies of 25 males with AS (including 16 who were diagnosed in adulthood).

Results

All patients showed normal positive staining of glomerular basement membranes and tubular basement membranes for COL4A2. Of the 25 patients, 10 (40%) patients showed loss of staining for COL4A5 (including 89% of children and 13% of adults) and the remaining 15 (60%) had intact staining for COL4A5. Compared with patients with intact staining for COL4A5, those with loss of staining had more prominent ultrastructural glomerular basement membrane alterations and were younger at the time of biopsy. By Kaplan-Meier survival analysis and Cox regression analysis, loss of staining for COL4A5 predicted earlier progression to overt proteinuria and stage 2 chronic kidney disease or worse. By multivariate Cox regression analysis, loss of staining for COL4A5 was an independent predictor of the development of overt proteinuria and stage 2 chronic kidney disease or worse.

Discussion

Thus, the COL4A5 expression pattern has an important prognostic value and it correlates with the severity of ultrastructural glomerular basement membrane alterations in males with AS. Loss of COL4A5 staining is uncommon in patients with AS diagnosed in their adulthood.

Clinicopathological features of acute kidney injury associated with immune checkpoint inhibitors

Immune checkpoint inhibitors (CPIs), monoclonal antibodies that target inhibitory receptors expressed on T cells, represent an emerging class of immunotherapy used in treating solid organ and hematologic malignancies. We describe the clinical and histologic features of 13 patients with CPI-induced acute kidney injury (AKI) who underwent kidney biopsy. Median time from initiation of a CPI to AKI was 91 (range, 21 to 245) days. Pyuria was present in 8 patients, and the median urine protein to creatinine ratio was 0.48 (range, 0.12 to 0.98) g/g. An extrarenal immune-related adverse event occurred prior to the onset of AKI in 7 patients. Median peak serum creatinine was 4.5 (interquartile range, 3.6-7.3) mg/dl with 4 patients requiring hemodialysis. The prevalent pathologic lesion was acute tubulointerstitial nephritis in 12 patients, with 3 having granulomatous features, and 1 thrombotic microangiopathy. Among the 12 patients with acute tubulointerstitial nephritis, 10 received treatment with glucocorticoids, resulting in complete or partial improvement in renal function in 2 and 7 patients, respectively. However, the 2 patients with acute tubulointerstitial nephritis not given glucocorticoids had no improvement in renal function. Thus, CPI-induced AKI is a new entity that presents with clinical and histologic features similar to other causes of drug-induced acute tubulointerstitial nephritis, though with a longer latency period. Glucocorticoids appear to be a potentially effective treatment strategy. Hence, AKI due to CPIs may be caused by a unique mechanism of action linked to reprogramming of the immune system, leading to loss of tolerance.

Changing Kidney Allograft Histology Early Posttransplant: Prognostic Implications of 1-Year Protocol Biopsies

Allograft histology 1 year posttransplant is an independent correlate to long-term death-censored graft survival. We assessed prognostic implications of changes in histology first 2 years posttransplant in 938 first kidney recipients, transplanted 1999-2010, followed for 93.4 ± 37.7 months. Compared to implantation biopsies, histology changed posttransplant showing at 1 year that 72.6% of grafts had minor abnormalities (favorable histology), 20.2% unfavorable histology, and 7.2% glomerulonephritis. Compared to favorable, graft survival was reduced in recipients with unfavorable histology (hazards ratio [HR] = 4.79 [3.27-7.00], p < 0.0001) or glomerulonephritis (HR = 5.91 [3.17-11.0], p < 0.0001). Compared to unfavorable, in grafts with favorable histology, failure was most commonly due to death (42% vs. 70%, p < 0.0001) and less commonly due to alloimmune causes (27% vs. 10%, p < 0.0001). In 80% of cases, favorable histology persisted at 2 years. However, de novo 2-year unfavorable histology (15.3%) or glomerulonephritis (4.7%) related to reduced survival. The proportion of favorable grafts increased during this period (odds ratio = 0.920 [0.871-0.972], p = 0.003, per year) related to fewer DGF, rejections, polyoma-associated nephropathy (PVAN), and better function. Graft survival also improved (HR = 0.718 [0.550-0.937], p = 0.015) related to better histology and function. Evolution of graft histologic early posttransplant relate to long-term survival. Avoiding risk factors associated with unfavorable histology relates to improved histology and graft survival.

Bortezomib-induced acute interstitial nephritis

Acute interstitial nephritis (AIN) is one of the important causes of acute kidney injury (AKI) resulting from inflammatory tubulointerstitial injury induced by medications, infections and systemic diseases. Bortezomib has been increasingly used especially in renal related indications such as multiple myeloma and monoclonal gammopathy of renal significance. Severe allergic reactions from bortezomib treatment including AIN have not been described in the literature. We report a 47-year-old white man who developed biopsy-proven allergic AIN after treatment with bortezomib for his C3 glomerulonephritis. The patient's kidney function improved after treatment with glucocorticoid therapy and discontinuation of bortezomib, but worsened with recurrent AKI episode after re-initiation of bortezomib. His renal function improved after glucocorticoid therapy and discontinuation of bortezomib. To our knowledge, this is the first report of a biopsy-proven AIN from bortezomib.

Renal extramedullary hematopoiesis: interstitial and glomerular pathology

Renal extramedullary hematopoiesis is rarely recognized in the antemortem setting. We identified 14 patients with renal extramedullary hematopoiesis on antemortem specimens from 1994 to 2015. The mean age was 68 years (range 47-87 years); males predominated (M:F=9:5). All presented with renal insufficiency, including five (36%) with acute kidney injury. The mean serum creatinine at biopsy was 2.9 mg/dl (range 1.2-7.3 mg/dl). All had proteinuria (mean 7.9 g/24 h; range 0.5-28; n=13), including 9 with ≥3 g/24 h. Renal extramedullary hematopoiesis appeared histologically as an interstitial infiltrate (n=12) and/or a perirenal infiltrate (n=3) or mass-like lesion (n=1). Five were misdiagnosed as interstitial nephritis. Concurrent glomerular disease was prevalent and included fibrillary-like glomerulonephritis (n=3), chronic thrombotic microangiopathy (n=5), focal segmental glomerulosclerosis (n=6), and diabetic glomerulosclerosis (n=2). All patients had an underlying hematologic malignancy: primary myelofibrosis in 9, myeloproliferative neoplasm not otherwise specified in 1, essential thrombocythemia in 1, polycythemia vera in 1, and plasma cell myeloma in 2. Clinical follow-up was available in 12 patients, mean of 29 months (range 4-120 months). In 10 patients for whom treatment history could be obtained, 9 were treated with chemotherapy, and 1 was treated with steroids. The mean creatinine at last follow-up was 2 mg/dl (range 1.2-3.9 mg/dl) (n=9). Ten patients died in the follow-up period from their underlying hematological disease and had persistent renal disease. The two remaining patients had persistent chronic kidney disease. Renal extramedullary hematopoiesis should be considered in the differential diagnosis of interstitial infiltrates, particularly in the presence of a glomerulopathy and a hematologic malignancy.

Rapidly progressive glomerulonephritis due to coexistent anti-glomerular basement membrane disease and fibrillary glomerulonephritis

Anti-glomerular basement membrane (anti-GBM) disease is a major cause of rapidly progressive glomerulonephritis (RPGN). On the other hand, fibrillary glomerulonephritis (GN) typically presents as proteinuria, hematuria and renal insufficiency, but rarely as RPGN. Without electron microscopy, the diagnosis of fibrillary GN can be missed. We report a 68-year-old white woman who presented with RPGN with kidney biopsy demonstrating diffuse crescentic GN on light microscopy. By immunofluorescence, there was bright linear staining of the GBMs and smudgy mesangial staining for immunoglobulin G, C3, and kappa and lambda light chain. Electron microscopy revealed fibrillary deposits in the GBM and mesangium. A serum test for anti-GBM antibody was positive. To our knowledge, this is the first report of coexistence of fibrillary GN in a patient with anti-GBM disease. Electron microscopy is critical to identify the coexistence of other GN in patients presenting with crescentic GN.

Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN

Renal pathologists and nephrologists met on February 20, 2015 to establish an etiology/pathogenesis-based system for classification and diagnosis of GN, with a major aim of standardizing the kidney biopsy report of GN. On the basis of etiology/pathogenesis, GN is classified into the following five pathogenic types, each with specific disease entities: immune-complex GN, pauci-immune GN, antiglomerular basement membrane GN, monoclonal Ig GN, and C3 glomerulopathy. The pathogenesis-based classification forms the basis of the kidney biopsy report. To standardize the report, the diagnosis consists of a primary diagnosis and a secondary diagnosis. The primary diagnosis should include the disease entity/pathogenic type (if disease entity is not known) followed in order by pattern of injury (mixed patterns may be present); score/grade/class for disease entities, such as IgA nephropathy, lupus nephritis, and ANCA GN; and additional features as detailed herein. A pattern diagnosis as the sole primary diagnosis is not recommended. Secondary diagnoses should be reported separately and include coexisting lesions that do not form the primary diagnosis. Guidelines for the report format, light microscopy, immunofluorescence microscopy, electron microscopy, and ancillary studies are also provided. In summary, this consensus report emphasizes a pathogenesis-based classification of GN and provides guidelines for the standardized reporting of GN.

Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN

Renal pathologists and nephrologists met on February 20, 2015 to establish an etiology/pathogenesis-based system for classification and diagnosis of GN, with a major aim of standardizing the kidney biopsy report of GN. On the basis of etiology/pathogenesis, GN is classified into the following five pathogenic types, each with specific disease entities: immune-complex GN, pauci-immune GN, antiglomerular basement membrane GN, monoclonal Ig GN, and C3 glomerulopathy. The pathogenesis-based classification forms the basis of the kidney biopsy report. To standardize the report, the diagnosis consists of a primary diagnosis and a secondary diagnosis. The primary diagnosis should include the disease entity/pathogenic type (if disease entity is not known) followed in order by pattern of injury (mixed patterns may be present); score/grade/class for disease entities, such as IgA nephropathy, lupus nephritis, and ANCA GN; and additional features as detailed herein. A pattern diagnosis as the sole primary diagnosis is not recommended. Secondary diagnoses should be reported separately and include coexisting lesions that do not form the primary diagnosis. Guidelines for the report format, light microscopy, immunofluorescence microscopy, electron microscopy, and ancillary studies are also provided. In summary, this consensus report emphasizes a pathogenesis-based classification of GN and provides guidelines for the standardized reporting of GN.

Membranoproliferative glomerulonephritis with masked monotypic immunoglobulin deposits

The diagnosis of membranoproliferative glomerulonephritis (MPGN) has recently undergone change from an electron microscopy-based classification scheme to one based largely on immunofluorescence findings. This change is due to the recognition that many of these cases are driven by abnormalities of the alternative complement cascade, resulting in the concept of C3 glomerulopathy. Here we reviewed our case files to identify those with an MPGN pattern that show false negative staining for monoclonal immunoglobulins by routine immunofluorescence. Monoclonal immunoglobulin deposits were unmasked by performing immunofluorescence on formalin-fixed paraffin embedded tissue after protease digestion. Clinico-pathological details of 16 such cases with a mean serum creatinine of 2.7 mg/dl and mean 24 h proteinuria of 7.1 g were then determined. Hypocomplementemia was present in two-thirds of patients. Fourteen patients had a paraprotein on serum immunofixation, all of which matched the biopsy immunofluorescence staining pattern. Bone marrow biopsy showed plasma cell dyscrasia or B-cell lymphoproliferative disorder in 13 patients. Ten of these patients had findings on biopsy most consistent with C3 glomerulonephritis prior to performing paraffin immunofluorescence. Thus a high index of suspicion is necessary to avoid misdiagnosis in these cases, as many would have been mistakenly diagnosed as C3 glomerulopathy or unclassified MPGN if paraffin immunofluorescence was not performed.

Positive crossmatch kidney transplant recipients treated with eculizumab: outcomes beyond 1 year

This study examined outcomes beyond 1 year in eculizumab-treated (EC) positive crossmatch kidney transplants (+XMKTx) compared to a historical control group. +XMKTx received desensitization with either plasma exchange (PE) alone (N = 48) or PE and EC (N = 30). EC, given for at least 1 month, was continued in the setting of persistently high DSA (B flow cytometric crossmatch [BFXM] >200) including: 4 weeks (n = 14); 9 weeks (n = 6), 6 months (n = 2), and 12 months (n = 8). All patients had at least 2 years follow-up. The incidence of acute clinical ABMR was lower in the EC group than controls (6.7% vs. 43.8% p < 0.01). Death-censored allograft survival was similar between groups. Chronic ABMR was the main cause of graft loss. On 1-year protocol biopsies, no differences were noted between EC and controls including: cg score >0, 26.7% versus 31.9% (p = 0.62), ptc score ≥ 2, 60.0% versus 60.0% (p = 1.00), or C4d + , 33.8% versus 13.5% (p = 0.08). A persistently high BFXM in EC-treated patients was associated with cg score >0 at 1 year, while EC appeared to protect against cg if the BFXM remained low. We conclude that despite decreasing acute clinical ABMR rates, EC treatment does not prevent chronic ABMR in recipients with persistently high BFXM after +XMKTx.

Isolated endarteritis and kidney transplant survival: a multicenter collaborative study

Isolated endarteritis of kidney transplants is increasingly recognized. Notably, microarray studies revealed absence of immunologic signatures of rejection in most isolated endarteritis biopsy samples. We investigated if isolated endarteritis responds to rejection treatment and affects kidney transplant survival. We retrospectively enrolled recipients of kidney transplant who underwent biopsies between 1999 and 2011 at seven American and Canadian centers. Exclusion criteria were recipients were blood group-incompatible or crossmatch-positive or had C4d-positive biopsy samples. After biopsy confirmation, patients were divided into three groups: isolated endarteritis (n=103), positive controls (type I acute T cell-mediated rejection with endarteritis; n=101), and negative controls (no diagnostic rejection; n=103). Primary end points were improved kidney function after rejection treatment and transplant failure. Mean decrease in serum creatinine from biopsy to 1 month after rejection treatment was 132.6 µmol/L (95% confidence interval [95% CI], 78.7 to 186.5) in patients with isolated endarteritis, 96.4 µmol/L (95% CI, 48.6 to 143.2) in positive controls (P=0.32), and 18.6 µmol/L (95% CI, 1.8 to 35.4) in untreated negative controls (P<0.001). Functional improvement after rejection treatment occurred in 80% of patients with isolated endarteritis and 81% of positive controls (P=0.72). Over the median 3.2-year follow-up period, kidney transplant survival rates were 79% in patients with isolated endarteritis, 79% in positive controls, and 91% in negative controls (P=0.01). In multivariate analysis, isolated endarteritis was associated with an adjusted 3.51-fold (95% CI, 1.16 to 10.67; P=0.03) risk for transplant failure. These data indicate that isolated endarteritis is an independent risk factor for kidney transplant failure.

Proliferative glomerulonephritis due to monoclonal deposition with organized substructures

A growing number of monoclonal gammopathy-associated kidney diseases recently have been recognized. We present the case of a 54-year-old man who presented with acute kidney injury and hypocomplementemia. Kidney biopsy confirmed the presence of immunoglobulin G κ pseudothrombi with intracytoplasmic crystals in glomeruli and tubules. Levels of κ free light chains were elevated without a detectable monoclonal gammopathy, and bone marrow biopsy results were normal. After the first course of rituximab, cyclophosphamide, and dexamethasone in addition to daily plasmapheresis, kidney function recovered within 2 weeks and dialysis therapy was discontinued. Treatment for monoclonal protein-induced kidney disease should be considered in the setting of progressive decreased kidney function, even in the absence of a circulating monoclonal protein or cellular clone of origin.

Donor Kidney Evaluation

In patients with end-stage renal disease, kidney transplantation is the best means to extend survival and offer a better quality of life. The current shortage of organs available for transplantation has led to an effort to expand the kidney donor pool, including the use of nonideal donor kidneys. Assessment of the quality of the donated kidney is essential, and would facilitate the decision to transplant a potential organ or discard it. Multiple clinical and histologic parameters have been examined to evaluate the donor kidney and relate the findings to the graft outcome, but clear-cut criteria are yet to be defined.

Antibody-mediated rejection despite inhibition of terminal complement

Terminal complement blockade has been shown to decrease the incidence of early acute antibody-mediated rejection (eAMR) in the first month after positive cross-match kidney transplant recipients, yet some patients still develop eAMR. The current study investigated possible mechanisms of eAMR despite eculizumab treatment. Of the 26 patients treated with eculizumab, two developed clinical eAMR and another patient developed histologic signs of eAMR without graft dysfunction ('subclinical eAMR'). Twenty-three did not have histologic injury on early surveillance biopsies. All 26 patients had therapeutic levels of eculizumab and showed complete blockade of complement in hemolytic assays. High levels of donor-specific alloantibody (DSA) including total IgG, IgG3, and C1q+ DSA were present in patients with and without eAMR, and none correlated well with eAMR. In contrast, IgM DSA was present in only four patients after transplantation: the two patients with clinical eAMR, one patient with subclinical AMR, and one patient without eAMR (P = 0.006 correlation with eAMR). Both clinical eAMR episodes were easily treated with plasma exchange which removed IgM more completely and rapidly than IgG, resulting in normalization of function and histology. These data suggest a possible role of antidonor IgM DSA in the pathogenesis of eAMR in patients treated with terminal complement blockade (ClinicalTrials.gov Identifier: NCT00670774).

Membranous nephropathy with crescents: a series of 19 cases

BACKGROUND

Membranous nephropathy (MN) with crescents is rare and, in the absence of lupus, usually is associated with anti-glomerular basement membrane (anti-GBM) nephritis or antineutrophil cytoplasmic antibody (ANCA)-positive glomerulonephritis. Only rare cases of crescentic MN without ANCA or anti-GBM have been reported.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

19 patients with ANCA- and anti-GBM-negative crescentic MN and no clinical evidence of systemic lupus.

OUTCOMES

Clinical features, kidney biopsy findings, laboratory results, treatment, and follow-up of patients with crescentic MN.

RESULTS

Mean age was 55 (range, 5-86) years. All patients presented with proteinuria (mean protein excretion, 11.5 [range, 3.3-29] g/d) and nearly all had hematuria; 16 of 19 (84%) patients had decreased estimated glomerular filtration rates (eGFRs; mean serum creatinine, 2.9 [range, 0.4-10] mg/dL; mean eGFR, 39.7 [range, 4 to >100] mL/min/1.73 m2). Glomeruli showed on average 25% (range, 2%-73%) involvement by crescents. All showed a membranous pattern; 7 showed mesangial and 2 showed segmental endocapillary proliferation. By immunofluorescence, all cases showed granular subepithelial immunoglobulin G (IgG) and κ and λ light chains, and all but one showed C3; 5 showed C1q or IgA. Electron microscopy revealed stages I-III MN; 38% of cases were M-type phospholipase A2 receptor (PLA2R) associated, indicating that at least some were primary MN. Follow-up clinical data were available for all patients (mean, 22 [range, 1.5-138] months). 14 patients received immunosuppressive therapy, and 2, only angiotensin-converting enzyme inhibitor/angiotensin receptor blocker therapy. 4 patients (21%) progressed to end-stage renal disease, at 0-9 months postbiopsy. Mean serum creatinine level of those without end-stage renal disease at follow-up was 1.7 (range, 0.5-4.1) mg/dL; mean eGFR was 53.3 (range, 16-103) mL/min/1.73 m2. 67% of patients had proteinuria with protein excretion≥1 (mean, 3.2) g/d at follow-up.

LIMITATIONS

Retrospective study.

CONCLUSIONS

Crescentic MN is a rare variant of MN that usually presents with heavy proteinuria, hematuria, and decline in GFR. The prognosis is variable and the disease may respond to therapy, but most patients develop a long-term decline in GFR.

Banff 2013 meeting report: inclusion of c4d-negative antibody-mediated rejection and antibody-associated arterial lesions

The 12th Banff Conference on Allograft Pathology was held in Comandatuba, Brazil, from August 19-23, 2013, and was preceded by a 2-day Latin American Symposium on Transplant Immunobiology and Immunopathology. The meeting was highlighted by the presentation of the findings of several working groups formed at the 2009 and 2011 Banff meetings to: (1) establish consensus criteria for diagnosing antibody-mediated rejection (ABMR) in the presence and absence of detectable C4d deposition; (2) develop consensus definitions and thresholds for glomerulitis (g score) and chronic glomerulopathy (cg score), associated with improved inter-observer agreement and correlation with clinical, molecular and serological data; (3) determine whether isolated lesions of intimal arteritis ("isolated v") represent acute rejection similar to intimal arteritis in the presence of tubulointerstitial inflammation; (4) compare different methodologies for evaluating interstitial fibrosis and for performing/evaluating implantation biopsies of renal allografts with regard to reproducibility and prediction of subsequent graft function; and (5) define clinically and prognostically significant morphologic criteria for subclassifying polyoma virus nephropathy. The key outcome of the 2013 conference is defining criteria for diagnosis of C4d-negative ABMR and respective modification of the Banff classification. In addition, three new Banff Working Groups were initiated.

Systemic karyomegaly with primary pulmonary presentation

Systemic karyomegaly is a distinct disorder characterized by progressive renal failure and enlarged, bizarre renal tubular epithelial cells. We report the first case of systemic karyomegaly with primary pulmonary presentation and present the first detailed characterization of the karyomegalic cells in lung tissue. A 33-year-old woman was evaluated for chronic and progressive restrictive lung disease, ultimately necessitating single-lung transplantation. Her post-transplant course was marked by graft dysfunction, respiratory decline and renal failure culminating in her death 97 days post-transplant. At autopsy, karyomegalic cells were identified in her kidneys, prompting a careful examination of her native lung and other tissue. Karyomegalic cells were identified in the alveolar epithelium and airway walls. Viral studies were negative. DNA ploidy studies revealed an abnormal ploidy status of the karyomegalic cells. The identification and characterization of systemic karyomegaly with symptomatic lung involvement expands the differential diagnosis for relatively young patients presenting with interstitial lung disease.

Disseminated microsporidiosis in a renal transplant recipient: case report and review of the literature

Microsporidia are opportunistic pathogens that usually cause a limited disease in the gastrointestinal tract. Occasionally, they can cause disseminated disease. In solid organ transplant recipients, disseminated disease has been reported only rarely. We describe a 68-year-old woman who presented with fever, cough, and acute kidney injury 6 months after kidney transplantation. Dissemination was confirmed by identification of microsporidial spores in urine and bronchoalveolar lavage fluid. Polymerase chain reaction analysis identified the species as Encephalitozoon cuniculi.

Renal amyloidosis: origin and clinicopathologic correlations of 474 recent cases

BACKGROUND AND OBJECTIVES

The kidney is the organ most commonly involved in systemic amyloidosis. This study reports the largest clinicopathologic series of renal amyloidosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study provides characteristics of 474 renal amyloidosis cases evaluated at the Mayo Clinic Renal Pathology Laboratory from 2007 to 2011, including age, sex, serum creatinine, proteinuria, type of amyloid, and tissue distribution according to type.

RESULTS

The type of amyloid was Ig amyloidosis in 407 patients (85.9%), AA amyloidosis in 33 (7.0%), leukocyte chemotactic factor 2 amyloidosis in 13 (2.7%), fibrinogen A α chain amyloidosis in 6 (1.3%), Apo AI, Apo AII, or Apo AIV amyloidosis in 3 (0.6%), combined AA amyloidosis/Ig heavy and light chain amyloidosis in 1 (0.2%), and unclassified in 11 (2.3%). Laser microdissection/mass spectrometry, performed in 147 cases, was needed to determine the origin of amyloid in 74 of the 474 cases (16%), whereas immunofluorescence failed to diagnose 28 of 384 light chain amyloidosis cases (7.3%). Leukocyte chemotactic factor 2 amyloidosis and Apo AI, Apo AII, or Apo AIV amyloidosis were characterized by diffuse interstitial deposition, whereas fibrinogen A α chain amyloidosis showed obliterative glomerular involvement. Compared with other types, Ig amyloidosis was associated with lower serum creatinine, higher degree of proteinuria, and amyloid spicules.

CONCLUSIONS

In the authors' experience, the vast majority of renal amyloidosis cases are Ig derived. The newly identified leukocyte chemotactic factor 2 amyloidosis form was the most common of the rarer causes of renal amyloidosis. With the advent of laser microdissection/mass spectrometry for amyloid typing, the origin of renal amyloidosis can be determined in >97% of cases.

C3 glomerulonephritis associated with monoclonal gammopathy: a case series

BACKGROUND

C3 glomerulonephritis (GN) is a proliferative GN resulting from glomerular deposition of complement factors due to dysregulation of the alternative pathway of complement. Dysregulation of the alternative pathway of complement may occur as a result of mutations or functional inhibition of complement-regulating proteins. Functional inhibition of the complement-regulating proteins may result from a monoclonal gammopathy.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

32 Mayo Clinic patients with C3 GN, 10 (31%) of whom had evidence of a monoclonal immunoglobulin in serum.

OUTCOMES

Clinical features, hematologic and bone marrow biopsy findings, kidney biopsy findings, kidney measures, complement pathway abnormalities, treatment, and follow-up of patients with C3 GN that was associated with a monoclonal gammopathy.

RESULTS

Mean age of patients with C3 GN associated with monoclonal gammopathy was 54.5 years. Bone marrow biopsy done in 9 patients revealed monoclonal gammopathy of undetermined significance in 5 patients, small lymphocytic lymphoma/chronic lymphocytic leukemia in one patient, and no abnormal clones in the other 3 patients. Kidney biopsy showed membranoproliferative GN with bright capillary wall C3 staining in all 10 patients. Evaluation of the alternative pathway of complement showed abnormalities in 7 of 9 patients tested. No mutation in complement-regulating proteins was detected in any patient. As an index case, one patient with C3 GN and chronic lymphocytic leukemia was treated with rituximab, cyclophosphamide, vincristine, and prednisone, and one patient with C3 GN and monoclonal gammopathy of undetermined significance was treated with dexamethasone and bortezomib. Both patients showed significant decreases in hematuria and proteinuria and stabilization of kidney function.

LIMITATIONS

Studies to show evidence of direct activation of the alternative pathway by monoclonal immunoglobulin were not done.

CONCLUSIONS

The study highlights the association of C3 GN and monoclonal gammopathy, in particular in the older population, and the importance of targeting the underlying hematologic malignancy as an approach to treating C3 GN.

The diagnosis and characteristics of renal heavy-chain and heavy/light-chain amyloidosis and their comparison with renal light-chain amyloidosis

Little is known about the rare entities of heavy- and light-chain amyloidosis (AHL) and heavy-chain amyloidosis (AH). Here, we report the renal and hematological characteristics, pathology, and outcome of 16 patients with renal AH/AHL (5 with AH and 11 with AHL) and compare them with 202 patients with renal light-chain amyloidosis (AL) diagnosed during the same time period. All cases were diagnosed by kidney biopsy that showed Congo red-positive deposits. Amyloid typing was done by laser microdissection and mass spectrometry (LMD/MS) on 12 patients or by immunofluorescence on four patients. All patients with renal AH/AHL were Caucasians, with a male/female ratio of 2.2 and a median age at biopsy of 63 years. Compared with patients with renal AL, those with renal AH/AHL had less frequent concurrent cardiac involvement, higher likelihood of having circulating complete monoclonal immunoglobulin, lower sensitivity of fat pad biopsy and bone marrow biopsy for detecting amyloid, higher incidence of hematuria, and better patient survival. The hematological response to chemotherapy was comparable with renal AL. In 42% of patients, AH/AHL could not have been diagnosed without LMD/MS. Thus, renal AH/AHL is an uncommon and underrecognized form of amyloidosis, and its diagnosis is greatly enhanced by the use of LMD/MS for amyloid typing. The accurate histological diagnosis of renal AH/AHL and distinction from AL may have important clinical and prognostic implications.