Renal amyloidosis: origin and clinicopathologic correlations of 474 recent cases

Biochemical profile of renal amyloidosis in a Latin American cohort

BACKGROUND

Two-thirds of patients with immunoglobulin light chain (AL) amyloidosis have renal involvement. The biochemical profile of kidney damage is poorly described.

METHODS

A cross-sectional study was conducted involving patients diagnosed with AL amyloidosis and renal involvement between January 1, 2010, and April 30, 2022 at the Hospital Italiano de Buenos Aires. Participants were retrospectively identified from the Institutional Amyloidosis Registry. Patients diagnosed with AL amyloidosis and evidence of renal involvement were included. Individuals with other types of amyloidosis were excluded. The selection process involved a thorough review of medical records and registry data to ensure accurate identification and inclusion of eligible participants.

RESULTS

Seventy-seven patients were included. At diagnosis, 90% of the subjects had proteinuria, with a median of 4.3 g/24 h, 61% had renal failure, and 47% presented nephrotic syndrome. Semi-automated urinary electrophoresis revealed 55% with non-selective and 21% with moderately selective glomerular proteinuria. Urine immunofixation indicated 64% with lambda monoclonal free light chains and 12% with kappa. Serum immunofixation demonstrated 48% with lambda monoclonal type and 25% with lambda IgG. At the time of diagnosis of AL amyloidosis, the median age was 66 years (IQR 53-72) and 49% were men. In addition to kidney involvement, other organs were also affected: heart in 53%, gastrointestinal system in 19%, peripheral nervous system in 16%, and liver in 16% of patients.

CONCLUSION

Our study provides a biochemical profile in renal amyloidosis due to immunoglobulin light chains in a Latin American population. Proteinuria emerged as the most common finding in this cohort with frequent multiorgan involvement.

2024 Update on Classification, Etiology, and Typing of Renal Amyloidosis: A Review

Amyloidosis is a protein folding disease that causes organ injuries and even death. In humans, 42 proteins are now known to cause amyloidosis. Some proteins become amyloidogenic as a result of a pathogenic variant as seen in hereditary amyloidoses. In acquired forms of amyloidosis, the proteins form amyloid in their wild-type state. Four types (serum amyloid A, transthyretin, apolipoprotein A-IV, and β2-macroglobulin) of amyloid can occur either as acquired or as a mutant. Iatrogenic amyloid from injected protein medications have also been reported and AIL1RAP (anakinra) has been recently found to involve the kidney. Finally, the mechanism of how leukocyte cell-derived chemotaxin 2 (ALECT2) forms amyloid remains unknown. This article reviews the amyloids that involve the kidney and how they are typed.

Kidney Transplant Outcomes in Amyloidosis: US National Database Study

BACKGROUND

We aimed to assess contemporary transplant outcomes among kidney recipients with amyloidosis, as the treatment and prognosis of amyloidosis have shown improvement over time.

METHODS

Using the US Organ Procurement and Transplantation Network database, we initially evaluated the changes in patient and graft survival among kidney recipients with amyloidosis from 2002 to 2021. We then compared transplant outcomes between recipients with amyloidosis versus those with diabetic and nondiabetic causes of kidney failure, creating 1:4 matches with highly similar characteristics separately for deceased donor kidney transplant (DDKT) and living donor kidney transplant (LDKT) during the last decade (2012-2021).

RESULTS

We identified 643 kidney recipients with amyloidosis during 2002-2021. Patient and death-censored graft survival improved over time. In the matching analysis for 207 DDKT and 166 LDKT recipients with amyloidosis during 2012-2021, patient survival was not significantly different between amyloidosis and diabetes groups in both DDKT (log-rank, P = 0.057) and LDKT (P = 0.99). Compared with the nondiabetes group, patient survival in the amyloidosis group was not significantly different for DDKTs (P = 0.56) but was significantly lower for LDKTs (P = 0.04). Death-censored graft failure risk was not significantly different between amyloidosis and diabetes or nondiabetes groups for both DDKTs (P = 0.78 and 0.75) and LDKTs (P = 0.40 and 0.24).

CONCLUSIONS

In this well-matched cohort study, we found no significant differences in patient and graft survival between kidney recipients with amyloidosis and those with diabetes. Similarly, these outcomes were not significantly different between those with amyloidosis versus nondiabetic causes, except for patient survival of LDKT recipients.

Long-Term Rehabilitation Therapy Is Effective for Physical Function in a Patient With Amyloid Light Chain Amyloidosis Complicated by Nephrotic Syndrome: A Case Report and Literature Review

We report on the rehabilitation of a patient with amyloid light chain (AL) amyloidosis complicated by nephrotic syndrome. Various symptoms produced by AL amyloidosis, including nephrotic syndrome, complicate rehabilitation therapy. In this case report, long-term physical therapy was initiated prior to autologous peripheral blood stem cell transplantation owing to the risk of further decline in physical function due to decreased mobility and physical activity. Patients were instructed on how to perform home exercise therapy. Furthermore, compliance was monitored using a checklist and regular face-to-face feedback. There was no increase in skeletal muscle mass, but improvements in grip strength, lower extremity muscle strength, and phase angle were observed after 24 weeks of physical therapy. Despite the absence of partial remission (urinary protein level of 3.5 g/gCre or higher), nephrotic syndrome demonstrated a trend toward improvement. Since the effectiveness of physical therapy in such patients has not yet been fully established, this report suggests that long-term rehabilitation therapy for physical function in patients with nephrotic syndrome complicated by persistent proteinuria may be effective.

Immunotactoid Glomerulopathy

Immunotactoid glomerulopathy (ITG) is a rare glomerular disease that typically presents with proteinuria, hematuria, and kidney dysfunction. A kidney biopsy is essential to establish the diagnosis of ITG. ITG is characterized by glomerular electron-dense immunoglobulin deposits with hollow-cored microtubules. ITG is classified as either monoclonal or polyclonal based on immunofluorescence staining of the immunoglobulin deposits. Monoclonal ITG is associated with an underlying hematologic disorder in two-thirds of the cases, lymphoma and plasma cell dyscrasias being the most common. Polyclonal ITG is associated with autoimmune diseases but can be seen with hematologic disorders and chronic infections. Due to the preponderance of hematologic disorders in both monoclonal and polyclonal ITG, a thorough hematologic workup must be performed in all cases of ITG. In monoclonal ITG with a detectable clone, clone-directed therapy is administered to achieve hematologic remission, as the renal response is highly dependent on the hematologic response. In clone-negative monoclonal ITG, anti-B cell therapy is often used as a first-line therapy. Management of polyclonal ITG without an underlying hematologic disorder is poorly defined. Compared to monoclonal ITG, patients with polyclonal ITG have a higher risk of progression to end-stage kidney disease. Recurrence of ITG following kidney transplantation is common and is often associated with hematologic relapse.

Paraprotein-Mediated Glomerular Diseases

Paraproteinemias are a group of complex diseases associated with an overproduction of a monoclonal immunoglobulin that can cause a diversity of kidney disorders and end-organ damage. In this review, we focus on paraprotein-mediated glomerular diseases. Kidney biopsy plays a crucial role in diagnosing these disorders, enabling the identification of specific histological patterns. These lesions are categorized into organized (such as amyloidosis, immunotactoid glomerulopathy, fibrillary glomerulonephritis, cryoglobulinemic glomerulonephritis, and monoclonal crystalline glomerulopathies) and nonorganized deposits (such as monoclonal Ig deposition disease and proliferative glomerulonephritis with monoclonal Ig deposits) based on the characteristics of immunofluorescence findings and the ultrastructural appearance of deposits on electron microscopy. This review aims to provide an update, highlight, and discuss clinicopathological aspects such as definition, epidemiology, clinical manifestations, mechanisms of kidney injury, histological features, and diagnostic procedures.

Renal Response Criteria for Clinical Trials in Amyloid Light Chain Amyloidosis

Immunoglobin light chain (AL) amyloidosis is a rare disease characterized by organ deposition of amyloid fibrils, most commonly in the heart and kidney. Disease heterogeneity necessitates organ-specific assessment to determine prognosis and response or progression. To facilitate development of new therapies, the Amyloidosis Forum (a public-private partnership between the US Food and Drug Administration and the nonprofit Amyloidosis Research Consortium) held a series of meetings and formed multiple working groups to identify clinical trial end points and analytic strategies. This report summarizes the recommendations of Renal Working Group. Estimated glomerular filtration rate (eGFR) and proteinuria were selected to evaluate eligibility, response, and/or progression in the context of investigational clinical trials for patients with AL amyloidosis. Accurate response assessments at the earliest possible time point were emphasized. The context of use, specific patient population, and the investigational therapeutic mechanism should ultimately drive selection of appropriate end points to evaluate renal response/progression in AL amyloidosis clinical trials.

AA Amyloidosis: A Contemporary View

PURPOSE OF REVIEW

Amyloid A (AA) amyloidosis is an organ- or life-threatening complication of chronic inflammatory disorders. Here, we review the epidemiology, causes, pathogenesis, clinical features, and diagnostic and therapeutic strategies of AA amyloidosis.

RECENT FINDINGS

The incidence of AA amyloidosis has declined due to better treatment of the underlying diseases. Histopathological examination is the gold standard of diagnosis, but magnetic resonance imaging can be used to detect cardiac involvement. There is yet no treatment option for the clearance of amyloid fibril deposits; therefore, the management strategy primarily aims to reduce serum amyloid A protein. Anti-inflammatory biologic agents have drastically expanded our therapeutic armamentarium. Kidney transplantation is preferred in patients with kidney failure, and the recurrence of amyloidosis in the allograft has become rare as transplant recipients have started to benefit from the new agents. The management of AA amyloidosis has been considerably changed over the recent years due to the novel therapeutic options aiming to control inflammatory activity. New agents capable of clearing amyloid deposits from the tissues are still needed.

Non-Immunoglobulin Amyloidosis-Mediated Kidney Disease: Emerging Understanding of Underdiagnosed Entities

Amyloidosis is a complex group of rare disorders characterized by the deposition of misfolded proteins in the extracellular space of various tissues and organs, leading to progressive organ dysfunction. The kidneys constitute a very common site affected, most notably by immunoglobulin-mediated (light chain, heavy chain, and light and heavy chain amyloidosis), but other types that include serum amyloid A (AA) amyloidosis and leukocyte chemotactic factor 2 amyloidosis, along with mutant proteins in several hereditary forms of amyloidosis such as transthyretin, fibrinogen α-chain, gelsolin, lysozyme, and apolipoproteins AI/AII/AIV/CII/CIII amyloidosis have been incriminated as well. The clinical presentation is variable and can range from minimal proteinuria for leukocyte chemotactic factor 2 amyloidosis to a full-blown nephrotic syndrome for AA amyloidosis. Clinical correlation, genetic analysis, and adequate tissue typing through a kidney biopsy are essential to make the correct diagnosis, especially when a family history of amyloidosis is absent. Except for AA and transthyretin amyloidosis, the treatment is usually purely supportive. Kidney transplantation is an acceptable form of treatment for end-stage kidney disease in all types of non-Ig-mediated renal amyloidosis.

Global research trends and hotspots for leukocyte cell-derived chemotaxin-2 from the past to 2023: a combined bibliometric review

Leukocyte cell-derived chemotaxin-2 (LECT2) is an important cytokine synthesized by liver. Significant research interest is stimulated by its crucial involvement in inflammatory response, immune regulation, disease occurrence and development. However, bibliometric study on LECT2 is lacking. In order to comprehend the function and operation of LECT2 in human illnesses, we examined pertinent studies on LECT2 investigation in the Web of Science database, followed by utilizing CiteSpace, VOSview, and Scimago Graphica for assessing the yearly quantity of papers, countries/regions involved, establishments, authors, publications, citations, and key terms. Then we summarized the current research hotspots in this field. Our study found that the literature related to LECT2 has a fluctuating upward trend. "Angiogenesis", "ALECT2", "diagnosis", and "biliary atresia" are the current investigative frontiers. Our findings indicated that liver diseases (e.g. liver fibrosis and hepatic cell carcinoma), systemic inflammatory disease, and amyloidosis are the current research focus of LECT2. The current LECT2 research outcomes are not exceptional. We hope to promote the scientific research of LECT2 and exploit its potential for clinical diagnosis and treatment of related diseases through a comprehensive bibliometric review.

Advancing Renal Amyloidosis Care: The Role of Modern Diagnostic Techniques with the Potential of Enhancing Patient Outcomes

Renal amyloidosis is a set of complex disorders characterized by the deposition of amyloid proteins in the kidneys, which causes gradual organ damage and potential kidney failure. Recent developments in diagnostic methods, particularly mass spectrometry and proteome profiling, have greatly improved the accuracy of amyloid typing, which is critical for disease management. These technologies provide extensive insights into the specific proteins involved, allowing for more targeted treatment approaches and better patient results. Despite these advances, problems remain, owing to the heterogeneous composition of amyloid proteins and the varying efficacy of treatments based on amyloid type. Access to sophisticated diagnostics and therapy varies greatly, highlighting the global difference in renal amyloidosis management. Future research is needed to investigate next-generation sequencing and gene-editing technologies, like clustered regularly interspaced short palindromic repeats (CRISPR), which promise more profound insights into the genetic basis of amyloidosis.

Deactivation of the Unfolded Protein Response Aggravated Renal AA Amyloidosis in HSF1 Deficiency Mice

Systemic amyloid A (AA) amyloidosis, which is considered the second most common form of systemic amyloidosis usually takes place several years prior to the occurrence of chronic inflammation, generally involving the kidney. Activated HSF1, which alleviated unfolded protein response (UPR) or enhanced HSR, is the potential therapeutic target of many diseases. However, the effect of HSF1 on AA amyloidosis remains unclear. This study focused on evaluating effect of HSF1 on AA amyloidosis based on HSF1 knockout mice. As a result, aggravated amyloid deposits and renal dysfunction have been found in HSF1 knockout mice. In progressive AA amyloidosis, HSF1 deficiency enhances serum amyloid A production might to lead to severe AA amyloid deposition in mice, which may be related to deactivated unfolded protein response as well as enhanced inflammation. Thus, HSF1 plays a significant role on UPR related pathway impacting AA amyloid deposition, which can mitigate amyloidogenic proteins from aggregation pathologically and is the possible way for intervening with the pathology of systemic amyloid disorder. In conclusion, HSF1 could not only serve as a new target for AA amyloidosis treatment in the future, but HSF1 knockout mice also can be considered as a valuable novel animal model for renal AA amyloidosis.

Autosomal dominant chronic tubulointerstitial nephropathy: do not forget amyloidosis

Amyloidosis is a rare cause of inherited kidney disease, with most variants responsible for prominent glomerular involvement. In this issue, Kmochová et al. reported the first description of autosomal dominant medullary amyloidosis due to apolipoprotein A4 variants, resulting in slowly progressive chronic kidney disease with minimal proteinuria. Combining next-generation sequencing with histopathological studies incorporating Congo red staining and mass spectrometry should be considered in the diagnostic workup of hereditary tubulointerstitial disorders not identified after routine genetic testing.

Morphological findings in different subtypes of hepatic amyloid

The classic findings have been well described for light-chain amyloid involving the liver. In addition to light chain, however, many additional proteins are now known to be amyloidogenic and can involve the liver. A total of 58 surgical pathology specimens with amyloid deposits were analyzed for patterns of amyloid deposition, including amyloid from light chain lambda (N = 17), light chain kappa (N = 15), transthyretin (N = 15), serum amyloid A (N = 4), apolipoprotein A1 (N = 4), fibrinogen alpha (N = 2), LECT2 (N = 1). Amyloid deposits predominately targeted the liver vasculature, including the walls of the hepatic arteries, portal veins, and sinusoids. While there was overlap, light chain amyloid predominately involved the sinusoids, while transthyretin amyloid predominately targeted the hepatic arteries, especially the larger ones in the hilum and larger portal tracts. Serum amyloid A formed nodular deposits that started in the portal vasculature but then extended into the portal tract stroma, leading to large, bulbous, portal-based amyloid deposits. Apolipoprotein A amyloid also formed large portal-based nodules. Fibrinogen was mild and subtle on H&E and predominately affected portal veins. Amyloid deposits in hilar nerves were prominent with amyloid light chain, transthyretin, and apolipoprotein A1. In conclusion, the histology of hepatic amyloid is diverse and shows several distinct clusters of findings that can aide in recognition in surgical pathology specimens.

Systemic Amyloidosis and Kidney Transplantation: An Update

Amyloidosis is a heterogeneous disorder characterized by abnormal protein aggregate deposition that often leads to kidney involvement and end-stage kidney disease. With advancements in diagnostic techniques and treatment options, the prevalence of patients with amyloidosis requiring chronic dialysis has increased. Kidney transplantation is a promising avenue for extending survival and enhancing quality of life in these patients. However, the complex and heterogeneous nature of amyloidosis presents challenges in determining optimal referral timing for transplantation and managing post-transplantation course. This review focuses on recent developments and outcomes of kidney transplantation for amyloidosis-related end-stage kidney disease. This review also aims to guide clinical decision-making and improve management of patients with amyloidosis-associated kidney disease, offering insights into optimizing patient selection and post-transplant care for favorable outcomes.

AA amyloidosis With Ig-Dominant Staining and Diagnostically Unusual Features

Introduction

Although serum amyloid A (AA) amyloid may occasionally show nonspecific staining by immunofluorescence (IF), the correct diagnosis can usually be determined by integrating pathologic features and clinical scenario, and using AA amyloid immunohistochemistry (IHC) and/or mass spectrometry. A recent mass spectrometry-based study described false-positive Ig IF staining in a subset of AA amyloid cases.

Methods

We sought to delineate clinicopathologic features of AA amyloid with Ig-dominant staining by using a retrospective review.

Results

AA amyloid with Ig-dominant staining was identified in 10 patients from 5 institutions, representing 1.2% to 4% of AA amyloid kidney biopsies. Evidence of a monoclonal protein was documented in 0% to 2.7% of patients with AA amyloid screened for inclusion, but 30% of those with Ig-dominant staining. The patient population had equal sex distribution and presented at median age of 68.5 years with nephrotic proteinuria and kidney impairment. Etiologies of AA amyloid included injection drug use (30%), autoimmune disease (20%), and chronic infection (10%); 40% had no identified clinical association. On biopsy, heavy chain (co)dominant staining by IF (in 80%), discordant distribution in Ig staining (in 20%), tubulointerstitial nephritis (in 30%), and/or crescents (in 10%) were present. Two of 3 patients with paraproteinemia had concordant heavy and/or light chain dominant staining within the AA amyloid. Two cases were initially misdiagnosed as Ig-associated amyloidosis.

Conclusion

We describe the morphologic spectrum of AA amyloidosis with Ig-dominant staining which may have clinical, laboratory, and pathologic overlap with amyloid light chain (AL), amyloid heavy chain, and heavy and light chain (AHL) amyloidosis.

An Intriguing Case of Amyloidosis Leading to PAGE Kidney in a Post Renal Transplant Recipient: A Case Report

Amyloidosis is an infiltrative disease where amyloid fibrils get deposited in the organs like kidney, liver and spleen. Amyloid deposition in the kidneys classically meant deposition in the glomeruli and mesangium until 2008 when interstitial amyloid deposits were isolated and named as` Leukocyte cell-derived chemotaxin 2-associated amyloidosis. It is a progressive disease which clinically manifests as slowly progressive renal dysfunction and/or proteinuria. Our case 34 year old renal transplant recipient underwent graft biopsy post transplantation which revealed interstitial LECT-2 amyloid deposits. Unfortunately, he developed page kidney post biopsy which was managed conservatively with percutaneous drainage.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-022-01072-6.

Tubular basement membrane amyloid deposition: is it an indicator of renal progression in light chain amyloidosis?

In light chain amyloidosis (LA), the massive glomerular and vascular amyloid deposition leading to interstitial fibrosis/tubular atrophy (IFTA) is thought to be responsible for renal failure. The amyloid deposition in the interstitium and the tubular basement membrane (TBM) has received less attention in the study of LA. We, therefore, collected clinical and laboratory data on patients diagnosed with LA in our Nephrology Department and studied amyloid deposition in the TBM. Twelve LA patients were diagnosed by renal biopsy during a seven-year period. In 4 of the 12, amyloid deposition could also be detected in the TBM. In our first case of a patient with diabetes mellitus, non-amyloid fibrils resembling 'diabetic fibrillosis' were also seen by electron microscopy. Despite the double damage, IFTA was negligible, blood vessels were unaffected, and the glomerular deposition was segmental. In the other three cases, significant (>50%) IFTA and a severely reduced estimated glomerular filtration rate were already detected at the time of diagnosis and amyloid deposition was also observed in the blood vessels. These findings indicate the importance of TBM amyloid deposition in the progression of renal disease. This may represent a late-stage presentation of the disease with a heavy LC burden.

Characteristics of Complement Protein Deposition in Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposition

BACKGROUND

Hypocomplementemia and complement co-deposition with monoclonal immunoglobulins in glomeruli are not rare in proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID). Deposition of monoclonal immunoglobulins in glomeruli has been suggested to activate complement and cause kidney injury. However, the profiles of complement activation in PGNMID and their clinical and pathologic significance need to be clarified.

METHODS

Forty-six patients with PGNMID were enrolled. Proteomic analysis of glomeruli using laser microdissection and mass spectrometry was performed for ten patients with PGNMID to determine the composition of glomerular deposits. Kidney deposition of complement components was detected by immunohistochemistry and immunofluorescence. Urinary and plasma levels of complement components were measured by an enzyme-linked immunosorbent assay. Group differences were assessed using t tests or Mann-Whitney U tests depending on the distribution. Correlation analysis was performed using Spearman rank correlation or Pearson correlation.

RESULTS

Laser microdissection and mass spectrometry-based proteomic analysis showed that complement components were the most enriched proteins deposited in the glomeruli of patients with PGNMID. Glomerular deposition of C3c, C4d, and C5b-9 was detected in most patients. Levels of urinary and plasma C3a, C5a, soluble C5b-9, C4d, Bb, and C1q as well as urinary mannose-binding lectin were significantly higher in patients with PGNMID compared with healthy controls. The intensity of C3c and C4d deposition in glomeruli correlated with serum creatinine and the percentage of crescents, respectively. Furthermore, levels of urinary complement components correlated positively with serum creatinine, urinary protein excretion, percentage of crescents, and global glomerulosclerosis in kidney biopsies, whereas plasma levels of most complement components did not show a significant correlation with clinicopathologic parameters. In multivariable analysis, a higher level of urinary C4d was identified as an independent risk factor of kidney failure.

CONCLUSIONS

The complement system was found to be overactivated in PGNMID, and levels of urinary complements correlated with disease severity. A higher level of urinary C4d was identified as an independent risk factor of kidney failure.

Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation

A diverse spectrum of pathologically distinct, nonneoplastic, proliferative conditions of the kidneys and urinary tract demonstrate a expansile growth pattern similar to that of neoplasms. The renal pseudotumors include myriad causes of infections as well as rare noninfectious causes such as sarcoidosis, amyloidosis, and immunoglobulin G4-related disease (IgG4-RD). Rare entities such as cystitis cystica, endometriosis, nephrogenic adenoma, and pseudosarcomatous myofibroblastic proliferation and distinct types of prostatitis comprise tumefactive nontumorous disorders that affect specific segments of the urinary tract. The pseudotumors of the kidneys and urinary tract demonstrate characteristic histopathologic and epidemiologic features, as well as protean clinical manifestations, natural history, and imaging findings. Many patients present with genitourinary tract-specific symptoms or systemic disease. Some cases may be incidentally discovered at imaging. Some entities such as perinephric myxoid pseudotumors, IgG4-RD, fibroepithelial polyp, and nephrogenic adenoma display specific anatomic localization and disease distribution. Imaging features of multisystem disorders such as tuberculosis, sarcoidosis, and IgG4-RD provide supportive evidence that may allow precise diagnosis. Fungal pyelonephritis, xanthogranulomatous pyelonephritis, IgG4-RD, actinomycosis, and endometriosis show markedly low signal intensity on T2-weighted MR images. Although some pseudotumors exhibit characteristic imaging findings that permit correct diagnosis, laboratory correlation and histopathologic confirmation are required for definitive characterization in most cases. A high index of suspicion is a prerequisite for diagnosis. Accurate diagnosis is critical for instituting optimal management while preventing use of inappropriate therapies or interventions. Surveillance CT and MRI are frequently used for monitoring the response of pseudotumors to therapy. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Diagnostic performance of fluorescence microscopy with a tetramethylrhodamine isothiocyanate filter in identifying renal amyloidosis

BACKGROUND

Renal amyloidosis (RA) has a worldwide incidence of 5-13 cases per million person-years and is expected to rise in upcoming years due to growing awareness, plus improvement of diagnostic modalities. Diagnosing RA remains challenging, especially when encountering very small, focal, or early amyloid deposits. Since delays in diagnosis portends poor prognosis, high morbidity, and mortality, it is crucial to evaluate the performance of commonly used diagnostic modalities. This is the first study that presents a full picture of the diagnostic performance of fluorescence microscopy (FM) with a tetramethylrhodamine isothiocyanate (TRITC) filter to diagnose RA in general and stratified by compartments.

MATERIALS AND METHODS

A retrospective double-blind diagnostic accuracy study of FM-TRITC filter was performed. The presence or absence of amyloid in the vascular, interstitial, and glomerular compartments was established in 316 representative Congo red-stained core biopsies with an FM-TRITC filter. This was contrasted with polarized microscopy (PM) showing apple-green birefringence as the gold standard. Sensitivity, specificity, positive and negative predictive values, likelihood ratios, and the receiver operating characteristic (ROC) curve were obtained using STATA13.

RESULTS

The prevalence of RA was 6.01%, comparable with that reported in the literature. Reciprocity with regard to the location and pattern of fluorescence and birefringence between the two diagnostic modalities was seen. The FM-TRITC filter has a sensitivity of 100%, specificity of 97.64%, and a positive and negative predictive value of 73.08% and 100%, respectively. The positive likelihood ratio was 42.37, and the negative was 0.00. Overall accuracy was 97.78%. The area under the ROC curve was 0.98. The Diagnostic performance of the FM-TRITC filter stratified by compartments is shown in Table 1. The area under the ROC curve was 0.99, 0.98, and 0.99 for the vascular, interstitial, and glomerular compartment, respectively. All patients with RA (n = 19) were correctly identified; this included one new case, one case with small and focal amyloid, and two early cases with less dense amyloid where birefringence was ambiguous by PM.

DISCUSSION

The FM-TRITC filter is a highly accurate, sensitive, specific, with excellent predictive values, time-efficient, easy to perform, and suitable to reproduce diagnostic modality for RA. It can accurately rule out RA in all compartments, and in most cases concomitant use of PM should not be indispensable. The diagnosis of vascular, interstitial, and glomerular amyloid deposits can be done using only the FM-TRITC filter with Congo red-stained slides. Exceptionally, a few cases of interstitial amyloidosis could be overdiagnosed due to interferences (e.g. artefacts), these cases could be further assessed with a second diagnostic modality if positive fluorescence is seen. Routine use of the FM-TRITC filter can aid in the diagnosis of early RA, even when the deposits are inconspicuous by PM.

Hyperspectral Raman Imaging for Automated Recognition of Human Renal Amyloid

In the clinical setting, routine identification of the main types of tissue amyloid deposits, light-chain amyloid (AL) and serum amyloid A (AA), is based on histochemical staining; rarer types of amyloid require mass spectrometry analysis. Raman spectroscopic imaging is an analytical tool, which can be used to chemically map, and thus characterize, the molecular composition of fluid and solid tissue. In this proof-of-concept study, we tested the feasibility of applying Raman spectroscopy combined with artificial intelligence to detect and characterize amyloid deposits in unstained frozen tissue sections from kidney biopsies with pathologic diagnosis of AL and AA amyloidosis and control biopsies with no amyloidosis (NA). Raman hyperspectral images, mapped in a 2D grid-like fashion over the tissue sections, were obtained. Three machine learning-assisted analysis models of the hyperspectral images could accurately distinguish AL (types λ and κ), AA, and NA 93-100% of the time. Although very preliminary, these findings illustrate the potential of Raman spectroscopy as a technique to identify, and possibly, subtype renal amyloidosis.

Fibrinogen Aα-chain amyloidosis outbreaks in Japanese squirrels (Sciurus lis): a potential disease model

Fibrinogen Aα-chain amyloidosis is a hereditary systemic amyloidosis characterized by glomerular amyloid depositions, which are derived from the fibrinogen Aα-chain variant in humans. Despite its unique pathology, the pathogenic mechanisms of this disease are only partially understood. This is in part because comparative pathological studies on fibrinogen Aα-chain amyloidosis are currently unavailable as there is a lack of reported cases in animals other than humans. In this study, mass spectrometry-based proteomic analyses of Japanese squirrels (Sciurus lis) that died in five Japanese zoos showed that they developed glomerular-associated fibrinogen Aα-chain amyloidosis with an extremely high incidence rate (29/38 cases, 76.3%). The condition was found to be age-dependent in the Japanese squirrels, with 89% of individuals over 4 years of age affected. Mass spectrometry revealed that the C-terminal region of the fibrinogen Aα-chain was involved in amyloidogenesis in Japanese squirrels as well as humans. No gene variations were identified between amyloid-positive and amyloid-negative squirrels, which contrasted with the available data for humans. The results indicate that fibrinogen Aα-chain amyloidosis is a senile amyloidosis in Japanese squirrels. The results have also provided comparative pathological support that the amyloidogenic C-terminal region of the fibrinogen Aα-chain is involved in the characteristic glomerular pathology, regardless of the animal species. This study elucidates the potential causes of death in Japanese squirrels and will contribute to future comparative pathological studies of fibrinogen Aα-chain amyloidosis. © 2023 The Pathological Society of Great Britain and Ireland.

Pathological spectrum of hereditary transthyretin renal amyloidosis and clinicopathologic correlation: a French observational study

BACKGROUND

Cardiac and neurological involvements are the main clinical features of hereditary transthyretin (ATTRv) amyloidosis. Few data are available about ATTRv amyloid nephropathy (ATTRvN).

METHODS

We retrospectively included 30 patients with biopsy-proven ATTRvN [V30M (26/30) including two domino liver recipients, S77Y (2/30), V122I (1/30) and S50R (1/30) variants] from two French reference centers. We described the pathological features by comparing amyloid deposits distribution to patients with AL or AA amyloidosis, and sought to determine clinicopathological correlation with known disease-modifying factors such as TTR variant, gender and age at diagnosis.

RESULTS

In comparison with AL and AA amyloidosis, ATTRv patients had similar glomerular, arteriolar and arterial amyloid deposits, but more cortical and medullary tubulointerstitial (33%, 44%, 77%, P = .03) involvement. While the presence of glomerular deposits is associated with the range of proteinuria, some patients with abundant glomerular ATTRv amyloidosis had no significant proteinuria. V30M patients had more glomerular (100% and 25%, odds ratio = 114, 95% confidence interval 3.85-3395.00, P = .001) deposits, and higher estimated glomerular filtration rate [50 (interquartile range 44-82) and 27 (interquartile range 6-31) mL/min/1.73 m², P = .004] than non-V30M patients. We did not find difference in amyloid deposition according to gender or age at diagnosis.

CONCLUSION

ATTRvN affects all kidney compartments, but compared with AL/AA amyloidosis, ATTRvN seems to involve more frequently tubulointerstitial areas. V30M patients represents the dominant face of the disease with a higher risk of glomerular/arteriolar involvement. ATTRvN should thus be considered in patients, and potential relatives, with ATTRv amyloidosis and kidney dysfunction, regardless of proteinuria level.

Amyloidosis and the Kidney: An Update

Various types of systemic amyloidosis can wreak havoc on the architecture and functioning of the kidneys. Amyloidosis should be suspected in patients with worsening kidney function, proteinuria, and multisystem involvement, but isolated kidney involvement also is possible. Confirming the amyloidosis type and specific organ dysfunction is of paramount importance to select the appropriately tailored treatment and aim for better survival while avoiding treatment-associated toxicities. Amyloid renal staging in light chain amyloidosis amyloidosis helps inform prognosis and risk for end-stage kidney disease. Biomarker-based staging systems and response assessment guide the therapeutic strategy and allow the timely identification of refractory or relapsing disease so that patients can be switched to salvage therapy. Kidney transplantation is a viable option for selected patients with amyloidosis. Because of the complex nature of the pathophysiology and treatment of amyloidosis, a multidisciplinary team-based approach should be used in the care of these patients.

Non-Perturbative Identification and Subtyping of Amyloidosis in Human Kidney Tissue with Raman Spectroscopy and Machine Learning

Amyloids are proteins with characteristic beta-sheet secondary structures that display fibrillary ultrastructural configurations. They can result in pathologic lesions when deposited in human organs. Various types of amyloid protein can be routinely identified in human tissue specimens by special stains, immunolabeling, and electron microscopy, and, for certain forms of amyloidosis, mass spectrometry is required. In this study, we applied Raman spectroscopy to identify immunoglobulin light chain and amyloid A amyloidosis in human renal tissue biopsies and compared the results with a normal kidney biopsy as a control case. Raman spectra of amyloid fibrils within unstained, frozen, human kidney tissue demonstrated changes in conformation of protein secondary structures. By using t-distributed stochastic neighbor embedding (t-SNE) and density-based spatial clustering of applications with noise (DBSCAN), Raman spectroscopic data were accurately classified with respect to each amyloid type and deposition site. To the best of our knowledge, this is the first time Raman spectroscopy has been used for amyloid characterization of ex vivo human kidney tissue samples. Our approach, using Raman spectroscopy with machine learning algorithms, shows the potential for the identification of amyloid in pathologic lesions.

Renal function in aged C57BL/6J mice is impaired by deposition of age-related apolipoprotein A-II amyloid independent of kidney aging

Spontaneous and age-related amyloidosis has been reported in C57BL/6J mice; however, the biochemical characteristics of age-related amyloidosis remain unclear. Therefore, we herein investigated the age-related prevalence of amyloidosis, the types of amyloid fibril proteins, and the effects of amyloid deposition on renal function in C57BL/6J mice. The results obtained revealed a high incidence of amyloidosis in C57BL/6J mice originating from the Jackson laboratory as well as the deposition of large amounts of amyloid in the glomeruli of aged mice. We identified the amyloid fibril protein in C57BL/6J mice as wild-type apolipoprotein A-II. We induced renal amyloid deposition in 40-week-old mice, equivalent to that of spontaneous development in 80-week-old mice, to rule out the effects of aging, and revealed subsequent damage to kidney function by amyloid deposits. Furthermore, amyloid deposition in the mesangial region decreased podocyte density, compromised foot processes, and led to the accumulation of fibroblast growth factor 2 (FGF2) in glomeruli. Collectively, these results suggest that AApoAII deposition is a general pathology in aged C57BL/6J mice and is dependent on supplier colonies. Therefore, the effects of age-related amyloid deposition need to be considered in research on aging in mice.

Monoclonal gammopathy of renal significance: Multidisciplinary approach to diagnosis and treatment

Monoclonal gammopathy of renal significance (MGRS) is a hemato-nephrological term referring to a heterogeneous group of kidney disorders characterized by direct or indirect kidney injury caused by a monoclonal immunoglobulin (MIg) produced by a B cell or plasma cell clone that does not meet current hematologic criteria for therapy. MGRS-associated kidney diseases are diverse and can result in the development of end stage kidney disease (ESKD). The diagnosis is typically made by nephrologists through a kidney biopsy. Many distinct pathologies have been identified and they are classified based on the site or composition of the deposited Mig, or according to histological and ultrastructural findings. Therapy is directed towards the identified underlying clonal population and treatment decisions should be coordinated between hematologists and nephrologists in a multidisciplinary fashion, depend on the type of MGRS, the degree of kidney function impairment and the risk of progression to ESKD.

Renal AA amyloidosis: presentation, diagnosis, and current therapeutic options: a review

Amyloid A amyloidosis is thought to be the second most common form of systemic amyloidosis behind amyloidosis secondary to monoclonal Ig. It is the result of deposition of insoluble fibrils in the extracellular space of tissues and organs derived from the precursor protein serum amyloid A, an acute phase reactant synthesized excessively in the setting of chronic inflammation. The kidney is the most frequent organ involved. Most patients present with proteinuria and kidney failure. The diagnosis is made through tissue biopsy with involvement of the glomeruli in most cases, but also often of the vessels and the tubulointerstitial compartment. The treatment usually targets the underlying etiology and consists increasingly of blocking the inflammatory cascade of cytokines with interleukin-1 inhibitors, interleukin-6 inhibitors, and tumor necrosis factor-α inhibitors to reduce serum amyloid A protein formation. This strategy has also shown efficacy in cases where an underlying etiology cannot be readily identified and has significantly improved the prognosis of this entity. In addition, there has been increased interest at developing effective therapies able to clear amyloid deposits from tissues, albeit with mitigated results so far.

Leukocyte Chemotactic Factor 2 Amyloidosis (ALECT2) Distribution in a Mexican Population

OBJECTIVES

To assess the prevalence of leukocyte cell-derived chemotactic 2 (LECT2), its organ involvement, and its clinical association in autopsies from an ethnically biased population.

METHODS

The tissues from all autopsies of individuals diagnosed with amyloidosis were reassessed and typed for amyloid light chain (AL) amyloidosis, amyloid A (AA) amyloidosis, transthyretin amyloidosis (ATTR), and leukocyte chemotactic factor 2 amyloidosis (ALECT2) by immunohistochemistry. Organ involvement was described and correlated with its clinical associations.

RESULTS

Of 782 autopsies, 27 (3.5%) had a confirmed diagnosis of amyloidosis. Of these, 14 (52%) corresponded to ALECT2, 5 (19%) to AL amyloidosis, 2 (7%) to ATTR amyloidosis, 1 (4%) to AA amyloidosis, and 5 (21%) as undetermined-type amyloidosis. The LECT2 amyloid deposits were found in the kidneys, liver, spleen, and adrenal glands in most individuals. Except for the kidneys, there were no clinical signs suggestive of amyloid deposition in most of the affected organs. LECT2 amyloidosis was not associated with the cause of death in any case. No cases had heart or brain involvement. Potential subclinical effects of amyloid deposition in organs such as adrenal glands and spleen require further study.

CONCLUSIONS

This autopsy study confirms the high prevalence of LECT2 amyloidosis in the Mexican population, with frequent amyloid deposition in the kidneys, liver, spleen, and adrenal glands.

Kidney Biopsy Corner: Amyloidosis

Amyloidosis is an infiltrative disease caused by misfolded proteins depositing in tissues. Amyloid infiltrates the kidney in several patterns. There are, as currently described by the International Society of Amyloidosis, 14 types of amyloid that can involve the kidney, and these types may have different locations or clinical settings. Herein we report a case of AA amyloidosis occurring in a 24-year-old male with a history of intravenous drug abuse and provide a comprehensive review of different types of amyloids involving the kidney.

Current approaches to the diagnosis and management of amyloidosis

Amyloidosis is a collection of diseases caused by the misfolding of proteins that aggregate into insoluble amyloid fibrils and deposit in tissues. While these fibrils may aggregate to form insignificant localised deposits, they can also accumulate in multiple organs to the extent that amyloidosis can be an immediately life-threatening disease, requiring urgent treatment. Recent advances in diagnostic techniques and therapies are dramatically changing the disease landscape and patient prognosis. Delays in diagnosis and treatment remain the greatest challenge, necessitating physician awareness of the common clinical presentations that suggest amyloidosis. The most common types are transthyretin (ATTR) amyloidosis followed by immunoglobulin light-chain (AL) amyloidosis. While systemic AL amyloidosis was previously considered a death sentence with no effective therapies, significant improvement in patient survival has occurred over the past 2 decades, driven by greater understanding of the disease process, risk-adapted adoption of myeloma therapies such as proteosome inhibitors (bortezomib) and monoclonal antibodies (daratumumab) and improved supportive care. ATTR amyloidosis is an underdiagnosed cause of heart failure. Technetium scintigraphy has made noninvasive diagnosis much easier, and ATTR is now recognised as the most common type of amyloidosis because of the increased identification of age-related ATTR. There are emerging ATTR treatments that slow disease progression, decrease patient hospitalisations and improve patient quality of life and survival. This review aims to update physicians on recent developments in amyloidosis diagnosis and management and to provide a diagnostic and treatment framework to improve the management of patients with all forms of amyloidosis.

Clinicopathological Profile of Paraprotein-Associated Kidney Disease in Monoclonal Gammopathies: An Observational Study

Background Renal involvement in monoclonal gammopathies presents with different clinico-morphological patterns and can manifest at the onset or the late phase of hematological disease, or after chemotherapy. The spectrum is ever-expanding with advancements in diagnostic methods. Renal biopsy is needed for accurate diagnosis, as each of these patterns carries therapeutic and prognostic implications. Methods A total of 41 cases of monoclonal gammopathies were included in the study. Clinical, biochemical, and hematological details were obtained, and pathological variables were observed. Patients were followed till the maximum possible period, and treatment history and follow-up creatinine details were collected. Results The spectrum of renal biopsy lesions observed included light chain cast nephropathy (LCCN) n=19, amyloidosis n=11, monoclonal immunoglobulin deposition disease (MIDD) n=6, and proliferative glomerulonephritis with monoclonal immunoglobulin deposition (PGNMID) n=5; 10 of these cases can be categorized as monoclonal gammopathy of renal significance (MGRS). Acute kidney injury (AKI) (41%) is the predominant clinical presentation in general whereas the majority of amyloidosis cases presented with nephrotic and sub-nephrotic proteinuria. LCCN cases had high serum creatinine and calcium, positivity for M-spike, as well as a high FLC ratio, compared to the other types. Around 100% of LCCN and MIDD patients had myeloma and 100% of PGNMID cases had normal marrow. Conclusion More than three-fourths of patients were diagnosed with monoclonal gammopathies with biochemical and hematological workups after an initial kidney biopsy. The clinicopathological profile of these patients had a broad spectrum but there were still some consistent findings within the different types. A subgroup of patients (MGRS) had undetectable serum paraproteins but had monoclonal immunoglobulin deposition in the kidney.

A comprehensive mini-review on amyloidogenesis of different SARS-CoV-2 proteins and its effect on amyloid formation in various host proteins

Amyloidogenesis is the inherent ability of proteins to change their conformation from native state to cross β-sheet rich fibrillar structures called amyloids which result in a wide range of diseases like Parkinson's disease, Alzheimer's disease, Finnish familial amyloidosis, ATTR amyloidosis, British and Danish dementia, etc. COVID-19, on the other hand is seen to have many similarities in symptoms with other amyloidogenic diseases and the overlap of these morbidities and symptoms led to the proposition whether SARS-CoV-2 proteins are undergoing amyloidogenesis and whether it is resulting in or aggravating amyloidogenesis of any human host protein. Thus the SARS-CoV-2 proteins in infected cells, i.e., Spike (S) protein, Nucleocapsid (N) protein, and Envelope (E) protein were tested via different machinery and amyloidogenesis in them were proven. In this review, we will analyze the pathway of amyloid formation in S-protein, N-protein, E-protein along with the effect that SARS-CoV-2 is creating on various host proteins leading to the unexpected onset of many morbidities like COVID-induced Acute Respiratory Distress Syndrome (ARDS), Parkinsonism in young COVID patients, formation of fibrin microthrombi in heart, etc., and their future implications.

Idiopathic membranous nephropathy with renal amyloidosis: A case report

Background

Immunoglobulin light chain amyloidosis is a clonal, non-proliferative plasma cell disorder, in which fragments of immunoglobulin light chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic failure, peripheral/autonomic neuropathy, and atypical multiple myeloma. Membranous nephropathy (MN) is a group of diseases characterized by deposition of immune complexes under the epithelial cells of glomerular basement and diffuse thickening of the basement membrane. Most patients with idiopathic MN (IMN) have been exposed to phospholipase A2 receptor (PLA2R) antigen, and anti-PLA2R antibodies that attack podocytes can be detected in their blood. IMN combined with amyloidosis nephropathy without secondary factors is rare. The present study describes a patient with IMN combined with immunoglobulin light chain amyloidosis nephropathy.

Case report

A 39-year-old man was admitted to our hospital because of weight loss and edema. His clinical manifestation was nephrotic syndrome. Renal pathology revealed MN. A positive Congo red staining and the pathognomonic apple-green birefringence under cross-polarized light were considered to be associated with amyloid nephropathy. Immunofluorescence showed that λ light chain was positive. Heavy chain deposition disease and amyloid-associated protein amyloidosis were excluded by immunofluorescence and immunohistochemistry, respectively. Subsequent examinations showed that his serum was negative for antibodies against the PLA2R, but PLA2R was present in renal tissue. The final diagnosis was IMN with light chain amyloid nephropathy.

Conclusion

Renal amyloidosis accompanied by IMN is uncommon. Attention should be paid to the subtype of the disease and the exclusion of secondary factors. Perfect clinical and pathological examination are helpful for the classification and staging of the disease. Congo red staining, light microscopy, immunofluorescence, immunohistochemistry, electron microscopic examination, pathological tissue staining for PLA2R antigen and testing for anti-PLA2R antibody in serum are helpful.

Noninvasive Diagnostics of Renal Amyloidosis: Current State and Perspectives

Amyloidoses is a group of diseases characterized by the accumulation of abnormal proteins (called amyloids) in different organs and tissues. For systemic amyloidoses, the disease is related to increased levels and/or abnormal synthesis of certain proteins in the organism due to pathological processes, e.g., monoclonal gammopathy and chronic inflammation in rheumatic arthritis. Treatment of amyloidoses is focused on reducing amyloidogenic protein production and inhibition of its aggregation. Therapeutic approaches critically depend on the type of amyloidosis, which underlines the importance of early differential diagnostics. In fact, the most accurate diagnostics of amyloidosis and its type requires analysis of a biopsy specimen from the disease-affected organ. However, absence of specific symptoms of amyloidosis and the invasive nature of biomaterial sampling causes the late diagnostics of these diseases, which leads to a delayed treatment, and significantly reduces its efficacy and patient survival. The establishment of noninvasive diagnostic methods and discovery of specific amyloidosis markers are essential for disease detection and identification of its type at earlier stages, which enables timely and targeted treatment. This review focuses on current approaches to the diagnostics of amyloidoses, primarily with renal involvement, and research perspectives in order to design new specific tests for early diagnosis.

Renal amyloidosis: a new time for a complete diagnosis

Amyloidoses are a group of disorders in which soluble proteins aggregate and deposit extracellularly in tissues as insoluble fibrils, causing organ dysfunction. Clinical management depends on the subtype of the protein deposited and the affected organs. Systemic amyloidosis may stem from anomalous proteins, such as immunoglobulin light chains or serum amyloid proteins in chronic inflammation or may arise from hereditary disorders. Hereditary amyloidosis consists of a group of rare conditions that do not respond to chemotherapy, hence the identification of the amyloid subtype is essential for diagnosis, prognosis, and treatment. The kidney is the organ most frequently involved in systemic amyloidosis. Renal amyloidosis is characterized by acellular pathologic Congo red-positive deposition of amyloid fibrils in glomeruli, vessels, and/or interstitium. This disease manifests with heavy proteinuria, nephrotic syndrome, and progression to end-stage kidney failure. In some situations, it is not possible to identify the amyloid subtype using immunodetection methods, so the diagnosis remains indeterminate. In cases where hereditary amyloidosis is suspected or cannot be excluded, genetic testing should be considered. Of note, laser microdissection/mass spectrometry is currently the gold standard for accurate diagnosis of amyloidosis, especially in inconclusive cases. This article reviews the clinical manifestations and the current diagnostic landscape of renal amyloidosis.

Concurrence of leukocyte chemotactic factor 2-associated amyloidosis and autoimmune diseases: A case report

Leukocyte chemotactic factor 2-associated (ALECT2) amyloidosis is one of the recently reported types of amyloidosis, which is caused by the extracellular deposition of leukocyte chemotactic factor 2 (LECT2). There have not been any reports involving the concurrence of ALECT2 amyloidosis with Sjögren’s syndrome (SS) or systemic lupus erythematosus (SLE)s. Herein, we report a case of a 68-year-old Chinese woman presenting with long duration of sicca symptoms. The clinical evaluation and laboratory findings showed that she had SS overlapped with SLE. Kidney biopsy revealed a membranoproliferative glomerulonephritis (MPGN) with glomerular deposition of dominant IgG3-kappa by immunofluorescene, which was related to SS/SLE. Furthermore, patchy congophilic amyloid deposits in the tubulointerstitium were detected, which were positive for LECT2 protein by immunohistochemical staining and immunoelectron microscopy. This is the first case of ALECT2 amyloidosis that coexisted with SS/SLE, and the causal relationship between ALECT2 amyloidosis and autoimmune diseases remain unclear.

Monoclonal Gammopathy of Renal Significance: Histomorphological Spectrum at a Tertiary Care Center

Introduction

The term monoclonal gammopathy of renal significance (MGRS) has been described to include patients with renal manifestations associated with circulating monoclonal proteins with or without a clonal lymphoproliferation (B-cell or plasma cell) and not meeting diagnostic criteria for an overt hematological malignancy. A host of MGRS-associated lesions have been described that involve various renal compartments. Our study describes the histomorphological spectrum of MGRS cases at our center in the last 5 years and description as per the classification system of the International Kidney and Monoclonal Gammopathy Research Group (IKMG).

Material and Methods

Retrospective analysis was carried out of all the renal biopsies with characteristic monoclonal immunoglobulin lesions for histopathological diagnosis between years 2015 and 2020 and reviewed by two independent pathologists.

Results

Most patients in the study belonged to the fifth decade, with a median age of 50 years (mean 50.14 ± 10.43) range (24-68 years) with a male preponderance. Most patients presented with proteinuria as the sole manifestation (66.6%). Many of the patients (48%) had an M spike by serum protein electrophoresis or urinary protein electrophoresis with an abnormal serum free light chain assay (60.8%). AL amyloidosis was the most common diagnosis observed on histopathological evaluation (68.7%), followed by light chain deposition disease (10.4%).

Conclusion

MGRS lesions are infrequently encountered in the practice of nephropathology and pose a diagnostic challenge due to the limitation of a congruent clinical or hematological picture. A thorough histological examination with immunofluorescence and electron microscopy often precipitates in the right diagnosis and prompts timely management.

DES-Amyloidoses “Amyloidoses through the looking-glass”: A knowledgebase developed for exploring and linking information related to human amyloid-related diseases

More than 30 types of amyloids are linked to close to 50 diseases in humans, the most prominent being Alzheimer’s disease (AD). AD is brain-related local amyloidosis, while another amyloidosis, such as AA amyloidosis, tends to be more systemic. Therefore, we need to know more about the biological entities’ influencing these amyloidosis processes. However, there is currently no support system developed specifically to handle this extraordinarily complex and demanding task. To acquire a systematic view of amyloidosis and how this may be relevant to the brain and other organs, we needed a means to explore "amyloid network systems" that may underly processes that leads to an amyloid-related disease. In this regard, we developed the DES-Amyloidoses knowledgebase (KB) to obtain fast and relevant information regarding the biological network related to amyloid proteins/peptides and amyloid-related diseases. This KB contains information obtained through text and data mining of available scientific literature and other public repositories. The information compiled into the DES-Amyloidoses system based on 19 topic-specific dictionaries resulted in 796,409 associations between terms from these dictionaries. Users can explore this information through various options, including enriched concepts, enriched pairs, and semantic similarity. We show the usefulness of the KB using an example focused on inflammasome-amyloid associations. To our knowledge, this is the only KB dedicated to human amyloid-related diseases derived primarily through literature text mining and complemented by data mining that provides a novel way of exploring information relevant to amyloidoses.

AA Amyloidosis associated with cancers

Systemic AA amyloidosis is associated with systemic inflammatory processes such as autoimmune disorders or chronic infections. In addition, AA amyloidosis can develop in a localized or systemic form in patients with malignant neoplastic disorders, and usually involves kidneys impacting renal function. Among solid tumors, renal cell carcinoma (RCC) appears to be responsible for one-quarter to half of all cancers associated with amyloidosis. Among other solid cancers, various clinical presentation and pathological types of lung cancer and basal cell carcinoma skin were reported with AA amyloidosis more often than isolated case reports on other cancers with AA amyloidosis. Symptoms from kidney involvement rather than from the tumor per se were the presenting manifestations in cases of RCC associated with AA amyloidosis. Among hematological malignancies, clonal B cell/plasma cell dyscrasias such as monoclonal gammopathy and lymphoma were noted to be associated with AA amyloidosis. In addition, AA amyloidosis was reported in a substantial number of cases treated with immune checkpoint inhibitors such as pembrolizumab and nivolumab. The mechanism of association of cancer and AA amyloidosis seems to be mediated by the immune response exacerbated from the tumor and its microenvironment or immune therapy. The mainstay of treatment consists of therapy directed against the underlying malignancy or careful withdrawal of the offending agent. This review will discuss this rare but highly morbid clinical condition.

Renal Amyloidosis: Epidemiological, Clinical, and Laboratory Profile in Adults from One Nephrology Center

Background

Renal amyloidosis is one of the main differential diagnoses of nephrotic proteinuria in adults and the elderly. The aim of this study with the most important series in our country is to contribute to the epidemiological, clinical, and etiological study of the renal amyloidosis.

Methods

In a retrospective study carried out between 1975 and 2019, 310 cases of histologically proven and typed renal amyloidosis were selected for this study.

Results

There were 209 men and 101 women with a mean age of 53.8 ± 15.4 years (range, 17–84 years). Of the 310 cases, 255 (82.3%) were diagnosed with AA renal amyloidosis and 55 (17.7%) with non-AA amyloidosis. Infections were the main cause of AA amyloidosis, and tuberculosis was the most frequent etiology. The period from the onset of the underlying disease to diagnosis of the renal amyloidosis was an average of 177 months. The most frequent manifestations at the time of diagnosis were nephrotic syndrome (84%), chronic renal failure (30.3%), and end-stage renal disease (37.8%). After a medium follow-up of 16 months (range, 0–68 months), mortality occurred in 60 cases.

Conclusions

Given the high frequency of AA amyloidosis in our country, awareness of the proper management of infectious and chronic inflammatory diseases remains a priority in reducing the occurrence of this serious disease.

LECT2: A pleiotropic and promising hepatokine, from bench to bedside

LECT2 (leucocyte cell-derived chemotaxin 2) is a 16-kDa protein mainly produced by hepatocytes. It was first isolated in PHA-activated human T-cell leukaemia SKW-3 cells and originally identified as a novel neutrophil chemotactic factor. However, many lines of studies suggested that LECT2 was a pleiotropic protein, it not only functioned as a cytokine to exhibit chemotactic property, but also played multifunctional roles in some physiological conditions and pathological abnormalities, involving liver regeneration, neuronal development, HSC(haematopoietic stem cells) homeostasis, liver injury, liver fibrosis, hepatocellular carcinoma, metabolic disorders, inflammatory arthritides, systemic sepsis and systemic amyloidosis. Among the above studies, it was discovered that LECT2 could be a promising molecular biomarker and therapeutic target. This review summarizes LECT2-related receptors and pathways, basic and clinical researches, primarily in mice and human, for a better comprehension and management of these diseases in the future.

The Clinical Features and Outcomes of Renal Amyloidosis in Tunisia

Systemic amyloidosis is a rare disease characterized by clinical polymorphism. Indeed, the kidney is the most common organ involved and represents a real turning point in the disease. We aimed to determine the clinicopathological prognostic factors of renal amyloidosis (RA). We conducted a retrospective study including 40 cases with biopsy-proven RA collected in our department over a period of 10 years. Biochemical, demographic, and clinicopathological findings at diagnosis, as well as the follow-up data, were evaluated for each patient. The prevalence of amyloidosis was 2.7 per 100 nontransplant renal biopsies. The mean age at presentation was 55.5 ± 15.6 years with a male-to-female ratio of 1.85. The diagnosis of RA was confirmed by a renal biopsy in 85% of cases. Amyloid A (AA) amyloidosis was the most common type of amyloidosis (65%), and chronic infections ranked first in the panel of etiologies (41%). Amyloid light chain amyloidosis was mainly associated with multiple myeloma (57%). The median patient survival was 59 months versus 12 months for kidney survival. Age and extrarenal localization were independent predictors of mortality, whereas renal failure at presentation significantly influenced renal survival. The results of our study emphasize the rarity but also the severity of RA. AA amyloidosis was the most common type identified, which was mainly caused by chronic infections. Prevention remains the best solution until we can achieve therapeutic advances in inflammatory diseases.

A stepwise data interpretation process for renal amyloidosis typing by LMD-MS

Backgrounds

Systemic amyloidosis is classified according to the deposited amyloid fibril protein (AFP), which determines its best therapeutic scheme. The most common type of AFP found are immunoglobulin light chains. The laser microdissection combined with mass spectrometry (LMD-MS) technique is a promising approach for precise typing of amyloidosis, however, the major difficulty in interpreting the MS data is how to accurately identify the precipitated AFP from background.

Objectives

The objective of the present study is to establish a complete data interpretation procedure for LMD-MS based amyloidosis typing.

Methods

Formalin-fixed paraffin-embedded specimens from patients with renal amyloidosis and non-amyloid nephropathies (including diabetic nephropathy, fibrillary glomerulonephritis, IgA nephropathy, lupus nephritis, membranous nephropathy, and normal tissue adjacent to tumors) were analyzed by LMD-MS. Forty-two specimens were used to train the data interpretation procedure, which was validated by another 50 validation specimens. Area under receiver operating curve (AUROC) analysis of amyloid accompanying proteins (AAPs, including apolipoprotein A-IV, apolipoprotein E and serum amyloid P-component) for discriminating amyloidosis from non-amyloid nephropathies was performed.

Results

A stepwise data interpretation procedure that includes or excludes the types of amyloidosis group by group was established. The involvement of AFPs other than immunoglobulin was determined by P-score, as well as immunoglobulin light chain by variable of λ-κ, and immunoglobulin heavy chain by H-score. This achieved a total of 88% accuracy in 50 validation specimens. The AAPs showed significantly different expression levels between amyloidosis specimens and non-amyloid nephropathies. Each of the single AAP had a AUROC value more than 0.9 for diagnosis of amyloidosis from non-amyloid control, and the averaged level of the three AAPs showed the highest AUROC (0.966), which might be an alternative indicator for amyloidosis diagnosis.

Conclusions

The proteomic data interpretation procedure for LMD-MS based amyloidosis typing was established successfully that has a high practicability in clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02785-9.

Renal Amyloidosis: Presentation, Diagnosis, and Management

More than 35 amyloid precursor proteins have been identified and many have tropism for the kidney. Renal amyloidosis is most commonly seen in AL and AA amyloidosis and the main clinical manifestations are proteinuria and progressive renal dysfunction. On renal pathology, hallmark findings of amyloidosis include Congo red positivity with apple-green birefringence and randomly arranged fibrils measuring 7-12 nm in diameter on ultrastructural examination. Management of renal amyloidosis typically combines therapy targeting the underlying amyloid process and supportive management. Patients with renal amyloidosis who progress to end-stage renal disease can be treated with dialysis, and in selected patients, with renal transplantation.

Prognostic value of histopathological scoring and grading in patients with renal AA amyloidosis

OBJECTIVE

The amount and distribution pattern of amyloid deposits may contribute to renal function and outcome, given the great diversity of renal involvement in amyloidosis. The aim of this study was to analyze the impact of histological characteristics of patients with biopsy-proven renal AA amyloidosis (AAA) on renal outcome.

METHODS

Renal biopsies of 37 patients with AAA were re-evaluated. The distribution pattern of glomerular amyloid (GA) deposits was classified, the extent of amyloid deposits in glomeruli, vessel, and interstitium and other histopathologic lesions were scored, and renal amyloid prognostic score (RAPS) was determined by summing all scores. Their potential prognostic relevance on renal outcome was investigated.

RESULTS

GA and vascular amyloid (VA) deposits were noted in all cases, interstitial amyloid (IA) was detected in 70.2%. GA deposits were predominantly seen in diffuse mesengiocapillary fashions (class IV) (51.4%). GA class, the extent of GA, VA, IA deposit, and RAPS, as well as interstitial fibrosis (IF) and interstitial inflammation were correlated to renal function at diagnosis. During the median follow-up of 52 months, 13 patients developed doubling of serum creatinine or end stage renal disease and they had a higher degree of GA and VA load (p = 0.03 and p = 0.042, respectively) as compared to the remaining patients. VA load, but not GA and RAPS grade, was associated with poor renal outcome (HR 3.016, 95% CI 1.45-6.25, p = 0.003).

CONCLUSIONS

Baseline renal function is closely linked to the extent of AA amyloid deposit in renal parenchyma but only VA load was a predictor of renal outcome in AAA patients.

Somatostatin-derived amyloidosis: a novel type of amyloidosis associated with well-differentiated somatostatin-producing neuroendocrine tumours

OBJECTIVE

To report the clinicopathologic and proteomic characteristics of a novel form of amyloidosis derived from the precursor protein somatostatin.

MATERIALS AND METHODS

Cases were identified by searching the Mayo Clinic amyloid liquid chromatography and tandem mass spectrometry (LC-MS/MS) typing database from 1 January 2008 to 1 September 2020 for specimens with the amyloid signature proteins and abundant somatostatin, in the absence of other amyloid precursor proteins. All available medical records and pathologic materials were examined.

RESULTS

Somatostatin-derived amyloid deposits were found in four patients, two females and two males, with a median age of 61.5 years (range 47-73 years). One patient also had neurofibromatosis-1. The amyloid in each case was associated with a well-differentiated, somatostatin-producing neuroendocrine tumour arising in the small bowel or pancreas. The amyloid deposits were Congo Red-positive and were readily identified by LC- MS/MS analysis. Somatostatin was present exclusively in somatostatin-associated amyloid cases (p < .001), compared to small bowel and pancreas amyloidosis cases of other types. Long-term follow-up is available for one patient who is alive 6 years after initial presentation.

CONCLUSION

We propose that somatostatin-related amyloidosis is a novel localised human amyloid type that arises in association with well-differentiated somatostatin-producing enteropancreatic neuroendocrine tumours. Treatment of the associated neuroendocrine tumour may be adequate therapy for these patients.

Primary localized amyloidosis of the ureter with osseous metaplasia presenting as a suspicious ureteral mass

Primary amyloidosis of the ureter is a rare disease that is difficult to distinguish from urothelial carcinoma. Only 50 cases of primary ureter amyloidosis have been reported since it was first described in 1937. Of these, only five cases of ureter amyloidosis with osseous metaplasia were reported. In this study, we report the clinical presentation of ureter primary amyloidosis that presented as a mass with osseous metaplasia. The aim of this study is to provide clinicians with knowledge about the clinical/radiologic manifestation that raise the suspicion of amyloidosis, bearing in mind the importance of differentiating it from other “malignant” processes.