Leukocyte Cell-Derived Chemotaxin 2-Associated Amyloidosis: A Recently Recognized Disease with Distinct Clinicopathologic Characteristics

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.

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.

Mimicking kidney flow shear efficiently induces aggregation of LECT2, a protein involved in renal amyloidosis

Aggregation of leukocyte cell-derived chemotaxin 2 (LECT2) causes ALECT2, a systemic amyloidosis that affects the kidney and liver. Previous studies established that LECT2 fibrillogenesis is accelerated by the loss of its bound zinc ion and stirring/shaking. These forms of agitation create heterogeneous shear conditions, including air-liquid interfaces that denature proteins, that are not present in the body. Here, we determined the extent to which a more physiological form of mechanical stress-shear generated by fluid flow through a network of narrow channels-drives LECT2 fibrillogenesis. To mimic blood flow through the kidney, where LECT2 and other proteins form amyloid deposits, we developed a microfluidic device consisting of progressively branched channels narrowing from 5 mm to 20 μm in width. Shear was particularly pronounced at the branch points and in the smallest capillaries. Aggregation was induced within 24 h by shear levels that were in the physiological range and well below those required to unfold globular proteins such as LECT2. EM images suggested the resulting fibril ultrastructures were different when generated by laminar flow shear versus shaking/stirring. Importantly, results from the microfluidic device showed the first evidence that the I40V mutation accelerated fibril formation and increased both the size and the density of the aggregates. These findings suggest that kidney-like flow shear, in combination with zinc loss, acts in combination with the I40V mutation to trigger LECT2 amyloidogenesis. These microfluidic devices may be of general use for uncovering mechanisms by which blood flow induces misfolding and amyloidosis of circulating proteins.

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.

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.

Association between Leukocyte Cell-Derived Chemotaxin 2 and Metabolic and Renal Diseases in a Geriatric Population: A Pilot Study

LECT2 is not a routine diagnostic marker for any disease, but it has been associated with many pathologies, including systemic amyloidosis, rheumatoid arthritis, diabetes, atherosclerosis, and metabolic syndrome. With human aortic sections (n = 22) and sera from geriatric subjects (n = 79), we analyzed the relationships that could be observed between this protein and other parameters related to metabolic diseases. As a result, we observed a relatively high (r~0.8, p < 0.05) positive correlation between SRA and LECT2 and a negative correlation between EGFR and LECT2 (r~-0.4, p < 0.05). We observed LECT2 expression in macrophages, myocytes, and other aortic cells, with a tendency to be overexpressed in developed atherosclerotic plaques. We conclude that LECT2 exerts its chemotactic effects not only as a protein synthesized in the liver and secreted and circulating in the blood but also as a locally expressed protein within atherosclerotic plaque development. The LECT2-EGFR correlation suggests an association of this protein with loss of normal renal function. This fact can be associated with LECT2 amyloidosis, although it should be verified whether in the geriatric population there is indeed a widespread accumulation of LECT2 with the progression of aging or whether it is rather a marker of general deterioration of renal function.

Leukocyte cell-derived chemotaxin 2 correlates with pediatric non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), newly renamed metabolic dysfunction-associated liver disease (MASLD), is a leading cause of liver disease in children and adults. There is a paucity of data surrounding potential biomarkers and therapeutic targets, especially in pediatric NAFLD. Leukocyte cell-derived chemotaxin 2 (LECT2) is a chemokine associated with both liver disease and skeletal muscle insulin resistance. Our aim was to determine associations between LECT2 and common clinical findings of NAFLD in pediatric patients. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum LECT2 concentrations in children (aged 2-17 years) with and without NAFLD. LECT2 concentrations were then correlated to clinical parameters in NAFLD. Mean LECT2 was significantly elevated in children with NAFLD versus healthy controls (n = 63 vs. 42, 5.83 ± 1.98 vs. 4.02 ± 2.02 ng/mL, p < 0.005). Additionally, LECT2 had strong correlations with body mass index (BMI) (Pearson r = 0.301, p = 0.002). A LECT2 concentration of 3.76 mg/mL predicts NAFLD with a sensitivity of 90.5% and specificity of 54.8%. Principal component analysis and logistic regression models further confirmed associations between LECT2 and NAFLD status. This study demonstrates increased serum LECT2 concentrations in pediatric NAFLD, which correlates with BMI and shows strong predictive value within these patients. Our data indicate that LECT2 is a potential diagnostic biomarker of disease and should be further investigated in pediatric as well as adult NAFLD.

Mimicking Kidney Flow Shear Efficiently Induces Aggregation of LECT2, a Protein Involved in Renal Amyloidosis

Aggregation of leukocyte cell-derived chemotaxin 2 (LECT2) causes ALECT2, a systemic amyloidosis that affects the kidney and liver. Homozygosity of the I40V LECT2 mutation is believed to be necessary but not sufficient for the disease. Previous studies established that LECT2 fibrillogenesis is greatly accelerated by loss of its single bound zinc ion and stirring or shaking. These forms of agitation are often used to facilitate protein aggregation, but they create heterogeneous shear conditions, including air-liquid interfaces that denature proteins, that are not present in the body. Here, we determined the extent to which a more physiological form of mechanical stress-shear generated by fluid flow through a network of artery and capillary-sized channels-drives LECT2 fibrillogenesis. To mimic blood flow through the human kidney, where LECT2 and other proteins form amyloid deposits, we developed a microfluidic device consisting of progressively branched channels narrowing from 5 mm to 20 μm in width. Flow shear was particularly pronounced at the branch points and in the smallest capillaries, and this induced LECT2 aggregation much more efficiently than conventional shaking methods. EM images suggested the resulting fibril structures were different in the two conditions. Importantly, results from the microfluidic device showed the first evidence that the I40V mutation accelerated fibril formation and increased both size and density of the aggregates. These findings suggest that kidney-like flow shear, in combination with zinc loss, acts in combination with the I40V mutation to trigger LECT2 amyloidogenesis. These microfluidic devices may be of general use for uncovering the mechanisms by which blood flow induces misfolding and amyloidosis of circulating proteins.

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.

Bystander LECT2 amyloidosis in tumor nephrectomy

Pathologic evaluation of the non-neoplastic renal parenchyma in tumor nephrectomy specimens is critical and can detect both renal-limited and systemic pathologies. We report the case of a 69-year-old Punjabi male who underwent cytoreductive nephrectomy for advanced renal cell carcinoma after immunotherapy. We detected clinically unexpected leukocyte chemotactic factor 2 (LECT2) amyloidosis during pathologic analysis of the surrounding non-neoplastic renal parenchyma, which was confirmed by mass spectrometry. LECT2 amyloidosis occurs predominantly in Hispanic patients and has only rarely been described in Punjabi patients. This case highlights the importance of careful pathologic evaluation of the non-neoplastic renal parenchyma of nephrectomy specimens and raises awareness that LECT2 amyloidosis can occur outside of the typical demographic of Hispanic patients.

Current Understanding of Systemic Amyloidosis and Underlying Disease Mechanisms

Amyloidosis is a group of diverse disorders caused by misfolded proteins that aggregate into insoluble fibrils and ultimately cause organ damage. In medical practice, amyloidosis classification is based on the amyloid precursor protein type, of which amyloid immunoglobulin light chain, amyloid transthyretin, amyloid leukocyte chemotactic factor 2, and amyloid derived from serum amyloid A protein are the most common. Distinct mechanisms appear to be predominantly operational in the pathogenesis of particular types of amyloidosis, including increased protein precursor synthesis, somatic or germ line mutations, and inherent instability in the precursor protein in its wild form. An increased supply of misfolded proteins and/or a decreased capacity of the protein quality control systems can result in an imbalance that leads to increased circulation of misfolded proteins. Although the detection of mature fibrils is the basis for diagnosis of amyloidosis, a growing body of evidence has implicated the prefibrillar species as proteotoxic and key contributors to the development of the disease.

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.

Renal amyloidogenic leukocyte chemotactic factor 2 combined with IgA nephropathy: A case report

RATIONALE

Amyloidogenic leukocyte chemotactic factor 2 (ALECT2) was recently considered as a new clinicopathologic type of amyloid, which frequently affects kidney in adults and results in different degrees of renal insufficiency and failure with or without proteinuria. Here, we present a case of combining LECT2-associated renal amyloidosis with immunoglobulin (Ig)A nephropathy.

PATIENT CONCERNS

A 71-year-old Chinese man presented with edema of both lower extremities.

DIAGNOSES

There was pale eosinophilic material strongly positive for the Congo red stain in interstitium with demonstrated apple green birefringence under polarized light. Immunofluorescent stain was positive for IgA deposits (4+), IgG deposits (2+), C3 deposits (3+) within the mesangium and capillary wall. Immunohistochemistry was positive for κ (+), λ (2+) in mesangial area, and LECT2 (2+) in the interstitium. On electron microscopy, there were electron-dense deposits within mesangial area and subendothelial and randomly orientated and nonbranching fibrils 10 nm in size found in the interstitium areas. Liquid chromatography tandem mass spectrometry was performed on peptides extracted from Congo red-positive, microdissected areas of the paraffin-embedded kidney specimen. LECT 2-associated renal amyloidosis with IgA nephropathy was pathologically confirmed by renal biopsy.

INTERVENTIONS

Steroids (60 mg/d) were used to treat IgA nephropathy daily. Antihypertensive treatment was switched to an angiotensin-converting enzyme inhibitor.

OUTCOMES

One year after diagnosis, creatine remained stable in the normal range, and 24-hour proteinuria decreased to 2.9 g.

LESSONS

To date, ALECT2 has still not been comprehensively investigated. The findings of this research provide insights for concurrent IgA nephropathy with ALECT2.

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.

LECT-2 amyloidosis: what do we know?

Amyloidosis is a rare group of diseases characterized by abnormal folding of proteins and extracellular deposition of insoluble fibrils. It can be localized to one organ system or can have systemic involvement. The kidney is the most common organ to be involved in systemic amyloidosis often leading to renal failure and the nephrotic syndrome. The two most common types of renal amyloidosis are immunoglobulin light chain-derived amyloidosis (AL) and reactive amyloidosis (AA). A novel form of amyloidosis (ALECT2) derived from leukocyte chemotactic factor 2 (LECT-2) and primarily involving the kidneys was first described by Benson et al in 2008. The liver was subsequently identified as the second most common organ involved in ALECT2 amyloidosis. LECT-2 is a unique protein that can form amyloid deposits even in its unmutated form. Patients with ALECT2 present with minimal proteinuria in contrast to other forms of amyloidosis especially AL and AA. They may present with slightly elevated serum creatinine. Nephrotic syndrome and hematuria are rare. ALECT2 can be found in association with other types of amyloidosis as well as malignancies or autoimmune diseases. ALECT2 may be confused with amyloidosis associated with light and heavy chain monoclonal gammopathy if the immunofluorescence is positive with anti-light chain and anti-AA sera. The other organs involved are the duodenum, adrenal gland, spleen, prostate, gall bladder, pancreas, small bowel, parathyroid gland, heart, and pulmonary alveolar septa, but consistently uninvolved organs included brain and fibroadipose tissue. A renal biopsy along with characteristic features found on immunohistochemistry and mass spectrometry is diagnostic of ALECT2. ALECT2 should be suspected when all markers for AL and AA are negative. Proper diagnosis of ALECT2 can determine need for supportive care versus more aggressive interventions.

The molecular structure and role of LECT2 or CHM-II in arthritis, cancer, and other diseases

Leukocyte cell-derived chemotaxin-2 (LECT2 or LECT-2), also called chondromodulin II (ChM-II or CHM2) plays a versatile role in various tissues. It was first identified as a chemotactic factor to promote the migration of neutrophils. It was also reported as a hepatokine to regulate glucose metabolism, obesity, and nonalcoholic fatty liver disease. As a secreted factor, LECT2 binds to several cell surface receptors CD209a, Tie1, and Met to regulate inflammatory reaction, fibrogenesis, vascular invasion, and tumor metastasis in various cell types. As an intracellular molecule, it is associated with LECT2-mediated amyloidosis, in which LECT2 misfolding results in insoluble fibrils in multiple tissues such as the kidney, liver, and lung. Recently, LECT2 was found to be associated with the development of rheumatoid arthritis and osteoarthritis, involving the dysregulation of osteoclasts, mesenchymal stem cells, osteoblasts, chondrocytes, and endothelial cells in the bone microenvironment. LECT2 is implicated in the development of cancers, such as hepatocellular carcinoma via MET-mediated PTP1B/Raf1/ERK signaling pathways and is proposed as a biomarker. The mechanisms by which LECT2 regulates diverse pathogenic conditions in various tissues remain to be fully elucidated. Further research to understand the role of LECT2 in a tissue tropism-dependent manner would facilitate the development of LECT2 as a biomarker for diagnosis and therapeutic target.

Clinically occult amyloidosis derived from leukocyte chemotactic factor 2 (ALECT 2) with cardiac involvement complicating renal transplantation: case report and literature review

INTRODUCTION

Amyloidosis derived from leukocyte chemotactic factor 2 (ALECT2) may be associated with slowly progressive renal failure that is clinically unsuspected at the time of transplantation. While this is typically clinically insignificant, we report a case with extensive systemic ALECT2 amyloidosis that also involved the myocardium, contributing to perioperative death post renal transplantation.

CASE DESCRIPTION

A 72-year-old Hispanic woman presented for renal transplantation due to end-stage renal disease secondary to hypertension. She was bradycardic on admission. Cardiac workup prior to transplantation had not identified an infiltrative process. Post-transplant hypotensive bradycardic arrests lead to multiorgan failure, anoxic brain injury, and death. Autopsy revealed massive amyloid deposition in the native kidneys, adrenals, spleen, and less extensive infiltration of liver and myocardium. Cardiac intramural vasculature from venules to capillaries, arterioles, and arteries showed amyloid deposition. Mass spectrometry revealed ALECT2 as the amyloidogenic protein.

DISCUSSION

ALECT2 is a systemic amyloidosis that typically involves kidneys, adrenals, spleen, and liver. It may be clinically unsuspected at the time of renal transplantation and should be considered in older patients, especially from higher ALECT2 amyloid prevalence populations. Complications related to systemic disease may add to morbidity or mortality post-transplantation. Cardiac involvement in ALECT2 amyloidosis has not been previously identified as a significant clinical or autopsy finding, but our case demonstrates that the cardiovascular system may indeed rarely be involved by ALECT2 amyloidosis in cases with extensive systemic disease, and it may be associated with significant clinical sequelae.

The amyloid proteome: a systematic review and proposal of a protein classification system

Amyloidosis is a disease caused by pathological fibril aggregation and deposition of proteins in different tissues and organs. Thirty-six fibril-forming proteins have been identified. So far, proteomic evaluation of amyloid focused on the detection and characterization of fibril proteins mainly for diagnostic purposes or to find novel fibril-forming proteins. However, amyloid deposits are a complex mixture of constituents that show organ-, tissue-, and amyloid-type specific patterns, that is the amyloid proteome. We carried out a comprehensive literature review on publications investigating amyloid via liquid chromatography coupled to tandem mass spectrometry, including but not limited to sample preparation by laser microdissection. Our review confirms the complexity and dynamics of the amyloid proteome, which can be divided into four functional categories: amyloid proteome-category 1 (APC1) includes exclusively fibrillary proteins found in the patient; APC2 includes potential fibril-forming proteins found in other types of amyloid; and APC3 and APC4 summarizes non-fibril proteins-some being amyloid signature proteins. Our categorization may help to systemically explore the nature and role of the amyloid proteome in the manifestation, progression, and clearance of disease. Further exploration of the amyloid proteome may form the basis for the development of novel diagnostic tools, thereby enabling the development of novel therapeutic targets.

LECT2 Protects Nile Tilapia (Oreochromis niloticus) Against Streptococcus agalatiae Infection

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine that especially plays an important role in innate immune. However, the roles of LECT2 in the immune response of the economically important fish Nile tilapia (Oreochromis niloticus) against bacterial infection remains unclear. In this study, a lect2 gene from Nile tilapia (On-lect2) was identified, and its roles in the fish’s immune response against bacterial infection were determined and characterised. On-lect2 contains an open reading frame of 456 bp that encodes a peptide of 151 amino acids, as well as the conservative peptidase M23 domain. On-LECT2 is 62%–84% identical to other fish species and about 50% identical to mammals. The highest transcriptional level of On-lect2 was detected in the liver, whereas the lowest levels were detected in the other tissues. Moreover, the On-LECT2 protein is located mainly in the brain and head kidney. The transcriptional levels of On-lect2 substantially increased in the head kidney, brain, liver and spleen after Streptococcus agalactiae infection. Knockdown On-lect2 led to higher mortality due to liver necrosis or haemorrhage and splenomegaly. In vitro analysis indicated that the recombinant protein of On-LECT2 improved phagocytic activity of head kidney-derived macrophages. In vivo challenge experiments revealed several functions of On-LECT2 in the immune response of Nile tilapia against bacterial infection, including promotion of inflammation, reduction of tissue damages and improvement of survival rate.

Stress Response Is the Main Trigger of Sporadic Amyloidoses

Amyloidoses are a group of diseases associated with the formation of pathological protein fibrils with cross-β structures. Approximately 5-10% of the cases of these diseases are determined by amyloidogenic mutations, as well as by transmission of infectious amyloids (prions) between organisms. The most common group of so-called sporadic amyloidoses is associated with abnormal aggregation of wild-type proteins. Some sporadic amyloidoses are known to be induced only against the background of certain pathologies, but in some cases the cause of amyloidosis is unclear. It is assumed that these diseases often occur by accident. Here we present facts and hypotheses about the association of sporadic amyloidoses with vascular pathologies, trauma, oxidative stress, cancer, metabolic diseases, chronic infections and COVID-19. Generalization of current data shows that all sporadic amyloidoses can be regarded as a secondary event occurring against the background of diseases provoking a cellular stress response. Various factors causing the stress response provoke protein overproduction, a local increase in the concentration or modifications, which contributes to amyloidogenesis. Progress in the treatment of vascular, metabolic and infectious diseases, as well as cancers, should lead to a significant reduction in the risk of sporadic amyloidoses.

A case of renal and splenic LECT 2 amyloidosis: A recently recognized cause of renal and systemic amyloidosis

Amyloidosis has traditionally been of a few defined varieties, most commonly including light-chain amyloidosis (AL amyloidosis) and secondary amyloidosis due to chronic inflammation (AA amyloidosis). Apolipoprotein A-I/A-II cystatin C, gelsolin, lysozyme, fibrinogen alpha chain, beta 2 microglobulin, and transthyretin familial amyloidosis represent rarer but reported varieties. Ten years ago, the first reports linked leukocyte chemotactic factor 2 (LECT2) amyloidosis as a pathological agent identified as a novel class of amyloid-generating protein. Epidemiology suggested that this was a new cause of amyloidosis that is especially common in Hispanic patients and somewhat common among patients from the Middle East-North Africa (MENA) region. We report a case of splenic and renal LECT 2 amyloidosis in a 62-year- old Hispanic male with diabetes mellitus. After an unremarkable serological workup, LECT 2 amyloidosis was diagnosed on renal biopsy. The case presentation is reviewed as a typical presentation, and the literature is reviewed regarding this newly reported entity, resulting in infiltrative renal amyloidosis and chronic renal disease.

Gut microbiota, key to unlocking the door of diabetic kidney disease

This review discusses the influence of gut microbiota dysbiosis on diabetic kidney disease through metabolite profile changes and immune and inflammatory mechanisms. We also elaborate on the mechanism of dysbiosis in the onset and development of other kidney diseases.

This review presents scientific evidence on the pathophysiologic links between gut microbiota and diabetic kidney disease (DKD), highlighting the influence of gut microbiota dysbiosis on DKD through metabolite profile changes and immunologic mechanisms.

Donor-Derived ALECT2 Amyloidosis and Recurrent Fibrillary Glomerulonephritis in a Transplant Allograft

The occurrence of renal amyloidosis and fibrillary glomerulonephritis in the same biopsy specimen is exceptional and poses a diagnostic challenge. We describe the case of a non-Hispanic White patient with end-stage kidney disease due to fibrillary glomerulonephritis who received a second living donor kidney from a Hispanic individual. A 40-month–posttransplantation biopsy performed for an elevated serum creatinine level revealed interstitial congophilic deposits and glomerular noncongophilic fibrillary deposits, in addition to rejection. Separate laser microdissections of the glomerular and interstitial deposits followed by liquid chromatography–tandem mass spectrometry (LC MS/MS) revealed DNAJB9 peptide spectra in glomeruli and a peptide profile consistent with leukocyte chemotactic factor 2 (ALECT2) amyloidosis in the interstitium. Based on these findings, a 2-week–posttransplantation biopsy was re-reviewed and analyzed using LC MS/MS, which revealed a peptide profile consistent with ALECT2 amyloidosis in the interstitium, without peptide spectra for ALECT2 or DNAJB9 in glomeruli. The findings were consistent with donor-derived ALECT2 amyloidosis and recurrent fibrillary glomerulonephritis. At 49 months posttransplantation, allograft function was stable with minimal proteinuria. Thus, LC MS/MS was crucial to establish the accurate diagnosis of these 2 nephropathies characterized by fibrillary deposits. The indolent posttransplantation course suggests that donated kidneys with focal interstitial ALECT2 deposits may be suitable for transplantation but the deposits persist for many years.

Loss of bound zinc facilitates amyloid fibril formation of leukocyte-cell-derived chemotaxin 2 (LECT2)

Aggregation of the circulating protein leukocyte-cell-derived chemotaxin 2 (LECT2) causes amyloidosis of LECT2 (ALECT2), one of the most prevalent forms of systemic amyloidosis affecting the kidney and liver. The I40V mutation is thought to be necessary but not sufficient for ALECT2, with a second, as-yet undetermined condition being required for the disease. EM, X-ray diffraction, NMR, and fluorescence experiments demonstrate that LECT2 forms amyloid fibrils in vitro in the absence of other proteins. Removal of LECT2's single bound Zn2+ appears to be obligatory for fibril formation. Zinc-binding affinity is strongly dependent on pH: 9-13 % of LECT2 is calculated to exist in the zinc-free state over the normal pH range of blood, with this fraction rising to 80 % at pH 6.5. The I40V mutation does not alter zinc-binding affinity or kinetics but destabilizes the zinc-free conformation. These results suggest a mechanism in which loss of zinc together with the I40V mutation leads to ALECT2.

Rare, Yet Emerging Cause of Graft Dysfunction-ALECT 2 Amyloidosis

Amyloidosis is characterized by pathological deposition of abnormal protein aggregates in various tissues, AL protein being the commonest. Amyloidosis derived from leukocyte cell-derived chemotaxin 2 (LECT2) is a recently recognized form of amyloidosis in the United States with predominant involvement of kidney and liver. We present a case of ALECT2 renal amyloid in a transplant recipient who presented with gradual worsening of graft function and subnephrotic proteinuria. To our knowledge, this is first case of LECT2 amyloidosis from Northern India in a transplant recipient. There is no effective therapy for amyloidosis derived from leukocyte cell-derived chemotaxin 2.

Renal amyloidosis: an update on diagnosis and pathogenesis

Amyloidosis is a diverse group of protein conformational disorder which is caused by accumulation and deposition of insoluble protein fibrils in vital tissues or organs, instigating organ dysfunction. Renal amyloidosis is characterized by the acellular Congo red-positive pathologic deposition of amyloid fibrils within glomeruli and/or the interstitium. It is generally composed of serum amyloid A-related protein or an immunoglobulin light chain; other rare forms lysozyme, gelsolin, fibrinogen alpha chain, transthyretin, apolipoproteins AI/AII/AIV/CII/CIII; and the recently identified form ALECT2. This disease typically manifests with heavy proteinuria, nephrotic syndrome, and finally progression to end-stage renal failure. Early diagnosis of renal amyloidosis is arduous as its symptoms appear in later stages with prominent amyloid deposition. The identification of the correct type of amyloidosis is quite troublesome as it can be confused with another related form. Therefore, the exact typing of amyloid is essential for prognosis, treatment, and correct management of renal amyloidosis. The emanation of new techniques of proteomic analysis, for instance, mass spectroscopy/laser microdissection, has provided greater accuracy in amyloid typing. This in-depth review emphasizes on the clinical features, renal pathological findings, and diagnosis of the AL and non-AL forms of renal amyloidosis.

Plasma half-life and tissue distribution of leukocyte cell-derived chemotaxin 2 in mice

Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine that causes skeletal muscle insulin resistance. The circulating levels of LECT2 are a possible biomarker that can predict weight cycling because they reflect liver fat and precede the onset of weight loss or gain. Herein, to clarify the dynamics of this rapid change in serum LECT2 levels, we investigated the in vivo kinetics of LECT2, including its plasma half-life and tissue distribution, by injecting ¹²⁵I-labelled LECT2 into ICR mice and radioactivity tracing. The injected LECT2 was eliminated from the bloodstream within 10 min (approximate half-life, 5 min). In the kidneys, the radioactivity accumulated within 10 min after injection and declined thereafter. Conversely, the radioactivity in urine increased after 30 min of injection, indicating that LECT2 is mainly excreted by the kidneys into the urine. Finally, LECT2 accumulated in the skeletal muscle and liver until 30 min and 2 min after injection, respectively. LECT2 accumulation was not observed in the adipose tissue. These findings are in agreement with LECT2 action on the skeletal muscle. The present study indicates that LECT2 is a rapid-turnover protein, which renders the circulating level of LECT2 a useful rapid-response biomarker to predict body weight alterations.

Along for the Ride: Intrahepatic Cholangiocarcinoma with Concomitant LECT2 Amyloidosis

We present a case of a 69-year-old Hispanic male with a past medical history of type II diabetes mellitus who presented with a two-month history of abdominal pain. A CT scan was performed which identified a liver mass. Biopsy of the liver mass revealed infiltration of normal liver parenchyma by atypical glands surrounded by pale eosinophilic material. The atypical glands were positive for CK7, while negative for CK20, CDX-2, and TTF-1, consistent with intrahepatic cholangiocarcinoma. A Congo red stain was performed, which highlighted salmon-orange areas, some with a globular appearance, around the glands and within the sinusoids and vasculature. Under polarized light, these areas displayed apple-green birefringence. These findings were consistent with amyloidosis, which was further supported by identification of ALECT2- (leukocyte chemotactic factor-2-) type amyloid on mass spectrometry. To our knowledge, this is the first documented case of intrahepatic cholangiocarcinoma arising in association with LECT2 amyloidosis.

Renal leukocyte chemotactic factor 2 (ALECT2)-associated amyloidosis in Chinese patients

Background: Leukocyte chemotactic factor 2 (ALECT2) amyloidosis is one of the recently described types of amyloidosis. In this study, we reported the first large case series of renal ALECT2 amyloidosis in Chinese patients.Methods: We studied the prevalence, clinical characteristics, renal pathology, outcome and genetic features among seven patients diagnosed with renal ALECT2 amyloidosis at Peking University First Hospital of China from 2000 to 2018.Results: Seven patients were diagnosed with ALECT2 amyloidosis, representing 1.9% of the renal biopsy-proven amyloidosis cases. The mean age at diagnosis was 68 years without gender preference. The patients mainly manifested with varying impaired kidney function with a mean estimated glomerular filtration rate of 42.7 mL/min/1.73 m² (range 8.0-80.5) and proteinuria at 3.9 g/24 h (range 0.4-11.3). There were four ALECT2 amyloidosis patients with concurrent membranous nephropathy (MN), who presented a higher proteinuria (6.4 ± 4.0 g/24 h vs. 2.0 ± 1.8 g/24 h) and higher frequency of nephrotic syndrome (50% vs. 0) than patients with isolated ALECT2 amyloidosis. Renal biopsy showed strongly congophilic amyloid deposits distributed mainly in the renal cortical interstitium, as well as the glomerular mesangium, the inner layer of glomerular basement membrane (GBM), and vascular walls. Two patients with concurrent ALECT2 amyloidosis and MN showed mild amyloid deposits, which have not been identified as ALECT2 amyloidosis by IHC and LMD/MS methods. All patients were corroborated by immunoelectron microscopy to exhibit the specific location of LECT2 in the amyloid fibrils. Genetic analysis revealed no mutations but homozygosity for the G allele encoding valine at position 40 in the mature protein in all patients. Except for one patient who died 8 years later after he was diagnosed with ALECT2 amyloidosis, the others presented with relatively stable renal function during the mean follow-up period of 12.5 months.Conclusions: ALECT2 amyloidosis was the third most common type of renal amyloidosis in Chinese patients from a single centre. The majority of ALECT2 amyloidosis patients were of Han ethnicity, with a high rate of concurrent MN. The recognition and accurate diagnosis of renal ALECT2 amyloidosis should be considered in Chinese patients.

[Incidental finding of leukocyte cell-derived chemotaxin 2 - Associated amyloidosis in a liver]

Leukocyte cell-derived chemotaxin 2-associated amyloidosis (ALECT2) is a recently described of amyloidosis described in the United States in 2007. It is a systemic disease that is predominantly associated with some ethnics groups. ALECT2 is usually diagnosed on a kidney biopsy performed in the context of slowly progressive chronic renal disease but can also be found incidentally on a liver sample. We report the case of a Syrian patient who benefited from a partial hepatectomy for the treatment of multiple metastasis of a colorectal adenocarcinoma. Microscopic analysis of the surgical specimen revealed numerous amyloid deposits that did not match any of the usual forms of liver amyloidosis after immunohistochemistry typing. Some morphologic features of the deposits were highly suggestive of ALECT2. Complementary immunohistochemical study and mass spectrometry confirmed the diagnosis.

The Pathology of Amyloidosis in Classification: A Review

BACKGROUND

The amyloidoses are a rare and heterogeneous group of disorders that are characterized by the deposition of abnormally folded proteins in tissues ultimately leading to organ damage. The deposits are mainly extracellular and are recognizable by their affinity for Congo red and their yellow-green birefringence under polarized light. Current classification of amyloid in medical practice is based on the amyloid protein type. To date, 36 proteins have been identified as being amyloidogenic in humans.

SUMMARY

in clinical practice, it is critical to distinguish between treatable versus non-treatable amyloidoses. Moreover, amyloidoses with a genetic component must be distinguished from the sporadic types and systemic amyloidoses must be distinguished from the localized forms. Among the systemic amyloidoses, AL continues to be the most common amyloid diagnosis in the developed world; other clinically significant types include AA, ALECT2, and ATTR. The latter is emerging as an underdiagnosed type in both the hereditary and wild-type setting. Other hereditary amyloidoses include AFib, several amyloidoses derived from apolipoproteins, AGel, ALys, etc. In a dialysis setting, systemic amyloid derived from β2 microglobulin (Aβ2M) should be considered, although a very rare hereditary variant has also been reported; several amyloidoses may be typically associated with aging and several iatrogenic types have also emerged. Determination of the amyloid protein type is imperative before specific therapy can be implemented and the current methods are briefly summarized. A brief overview of the target organ involvement by amyloid type is also included. Key Messages: (1) Early diagnosis of amyloidosis continues to pose a significant challenge and requires the participation of many clinical and laboratory specialties. (2) Determination of the protein type is imperative before specific therapy can be implemented. (3) While mass spectrometry has emerged as the preferred method of amyloid typing, careful application of immune methods is still clinically useful but caution and experience, as well as awareness of the limitations of each method, are necessary in their interpretation. (4) While the spectrum of amyloidoses continues to expand, it is critical to distinguish between those that are currently treatable versus those that are untreatable and avoid causing harm by inappropriate treatment.

Multiple morphological phenotypes of monoclonal immunoglobulin disease on renal biopsy: Significance of treatment

Plasma cell dyscrasias frequently involve the kidney causing renal dysfunction. Multiple morphologic manifestations of κ light chain disease occurring simultaneously in the same kidney biopsy are uncommon and suggest local microenvironment effects in addition to structural properties of the light chain. A 61-year-old female presented with new onset renal failure and proteinuria. Serological workup revealed monoclonal gammopathy with elevated κ : λ ratio of 1,371. Renal biopsy revealed several paraprotein manifestations including κ light chain deposition disease, monoclonal fibrillary glomerulonephritis, cryocrystalglobulenemia and fibrillar/microtubular cast nephropathy. There was also incidental leukocyte chemotactic factor 2 amyloidosis (ALECT 2), negative for κ light chain and confirmed by immunohistochemistry (IHC). Bone marrow biopsy revealed 10 - 20% κ restricted plasma cells. The patient received 10 cycles of CyBorD (cyclophosphamide, bortezomib, and dexamethasone) chemotherapy. Renal function improved with decreased κ : λ ratio. Repeat bone marrow biopsy showed no evidence of abnormal plasma cells by IHC. The renal recovery demonstrates there may be response to chemotherapy irrespective of the morphologic manifestations of light chain-related injury. Additionally, if amyloid is not demonstrated to be of light chain origin, other amyloid types should be considered.

Amyloidosis: diagnosis and new therapies for a misunderstood and misdiagnosed disease

Amyloidosis is a group of diseases characterized by extracellular deposition of amyloid fibril complexes. Fibril deposition results in organ dysfunction and possible failure. Amyloidosis is regarded as a rare disease, but in general is underdiagnosed. The two main types of systemic amyloidosis are immunoglobulin light chain and transthyretin amyloidosis. The increased availability of noninvasive cardiac imaging, genetic testing and improved laboratory assays and protein identification methods have led to increased diagnosis. However, in many cases, the diagnosis is not made until the patient develops organ impairment. Earlier diagnosis is required to prevent irreversible organ failure. Novel treatments for immunoglobulin light chain and transthyretin amyloidosis that halt disease progression, prolong and increase quality of life have recently become available.

Fibrinogen alpha amyloidosis: insights from proteomics

Introduction: Systemic amyloidosis is a diverse group of diseases that, although rare, pose a serious health issue and can lead to organ failure and death. Amyloid typing is essential in determining the causative protein and initiating proper treatment. Mass spectrometry-based proteomics is currently the most sensitive and accurate means of typing amyloid. Areas covered: Amyloidosis can be systemic or localized, acquired or hereditary, and can affect any organ or tissue. Diagnosis requires biopsy, histological analysis, and typing of the causative protein to determine treatment. The kidneys are the most commonly affected organ in systemic disease. Fibrinogen alpha chain amyloidosis (AFib) is the most prevalent form of hereditary renal amyloidosis. Select mutations in the fibrinogen Aα (FGA) gene lead to AFib. Expert commentary: Mass spectrometry is currently the most specific and sensitive method for amyloid typing. Identification of the mutated fibrinogen alpha chain can be difficult in the case of 'private' frameshift mutations, which dramatically change the sequences of the expressed fibrinogen alpha chain. A combination of expert pathologist review, mass spectrometry, and gene sequencing can allow for confident diagnosis and determination of the fibrinogen alpha chain mutated sequence.

Diagnosis, pathogenesis and outcome in leucocyte chemotactic factor 2 (ALECT2) amyloidosis

Introduction

Renal biopsy series from North America suggest that leucocyte chemotactic factor 2 (ALECT2) amyloid is the third most common type of renal amyloid. We report the first case series from a European Centre of prevalence, clinical presentation and diagnostic findings in ALECT2 amyloidosis and report long-term patient and renal outcomes for the first time.

Methods

We studied the clinical features, diagnostic investigations and the outcome of all patients with ALECT2 amyloidosis followed systematically at the UK National Amyloidosis Centre (NAC) between 1994 and 2015.

Results

Twenty-four patients, all non-Caucasian, were diagnosed with ALECT2 amyloidosis representing 1.3% of all patients referred to the NAC with biopsy-proved renal amyloid. Diagnosis was made at median age of 62 years, usually from renal histology; immunohistochemical staining was definitive for ALECT2 fibril type. Median estimated glomerular filtration rate (GFR) at diagnosis was 33 mL/min/1.73 m2 and median proteinuria was 0.5 g/24 h. Hepatic amyloid was evident on serum amyloid P component (SAP) scintigraphy in 11/24 cases but was not associated with significant derangement of liver function. No patient had evidence of cardiac amyloidosis or amyloid neuropathy. Median follow-up was 4.8 (range 0.5-15.2) years, during which four patients died and four progressed to end-stage renal disease. The mean rate of GFR loss was 4.2 (range 0.5-9.6) mL/min/year and median estimated renal survival from diagnosis was 8.2 years. Serial SAP scans revealed little or no change in total body amyloid burden.

Conclusions

ALECT2 amyloidosis is a relatively benign type of renal amyloid, associated with a slow GFR decline, which is reliably diagnosed on renal histology. Neither the molecular basis nor the factors underlying the apparent restriction of ALECT2 amyloidosis to non-Caucasian populations have been determined.

Epidemiology and Pathophysiology of Glomerular C4d Staining in Native Kidney Biopsies

Introduction

Routine C4d staining in renal transplantation has stimulated its use in kidney biopsies with glomerulonephritis (GN). Methodical description on staining patterns in the native kidney is not available.

Methods

We retrospectively evaluated C4d staining in formalin-fixed paraffin-embedded sections from 519 native kidney biopsies (bx) with and without glomerular disease.

Results

Strong C4d staining was consistently present in immune-complex GN, including lupus nephritis (LN) (n = 68), membranous GN (n = 24), membranoproliferative glomerulonephritis (MPGN) pattern (n = 22), fibrillary GN (n = 3), and proliferative GN with monoclonal IgG (n = 3). C4d stained all cases of postinfectious GN (n = 7) amyloidosis (n = 20) and C1q GN (n = 3). In contrast, IgA nephropathy (IgAN) (n = 34), was negative in 62% of bx, with the rest staining variably. The E1 Oxford classification score correlated with capillary wall C4d staining (P = 0.05). C4d marked the glomerular and arteriolar lesions in thrombotic microangiopathy (TMA; n = 16), the glomerular sclerotic segments in focal segmental glomerulosclerosis (FSGS; n = 77), and marked areas of necrosis in crescentic GN (n = 21). In diabetic glomerulopathy (n = 70), C4d marked advanced insudative lesions but was negative otherwise. C4d weakly stained the mesangium, or was negative in normal biopsies (n = 13), minimal change disease (MCD; n = 21), thin basement membrane disease (n = 20), Alport (n = 3), IgM nephropathy (n = 2), C3 glomerulopathy (n = 5), acute interstitial nephritis (n = 12), acute tubular necrosis (n = 22), ischemic glomerulopathy/nephrosclerosis (n = 23), and other miscellaneous processes (n = 14). Staining in tubular basement membranes and peritubular capillaries was most common in lupus.

Conclusion

Based on reliable staining in lupus and membranous GN, C4d staining is potentially useful as a screening and diagnostic tool, if only paraffin-embedded tissue is available. Knowledge of C4d staining patterns in normal and pathological tissues enhances its diagnostic value.

De novo leukocyte chemotactic factor 2 amyloidosis in a pediatric renal allograft, 15 years post-transplant

Leukocyte chemotactic factor 2 amyloidosis (ALECT2) is a recently described form of systemic amyloidosis, which most commonly affects the kidney and liver. The LECT2 protein is produced during inflammatory processes, but its precise function in renal diseases in unclear. ALECT2, however, is known to be a relatively common form of renal amyloidosis, after amyloid light chain and serum amyloid A types and is most often seen in patients of Hispanic ethnicity. ALECT2 can occur de novo or as recurrent disease in kidney transplants. We present the first case, to our knowledge, of de novo ALECT2 in a pediatric kidney transplant patient, 15 years post-transplant.

Systemic immunoglobulin light chain amyloidosis

Systemic immunoglobulin light chain amyloidosis is a protein misfolding disease caused by the conversion of immunoglobulin light chains from their soluble functional states into highly organized amyloid fibrillar aggregates that lead to organ dysfunction. The disease is progressive and, accordingly, early diagnosis is vital to prevent irreversible organ damage, of which cardiac damage and renal damage predominate. The development of novel sensitive biomarkers and imaging technologies for the detection and quantification of organ involvement and damage is facilitating earlier diagnosis and improved evaluation of the efficacy of new and existing therapies. Treatment is guided by risk assessment, which is based on levels of cardiac biomarkers; close monitoring of clonal and organ responses guides duration of therapy and changes in regimen. Several new classes of drugs, such as proteasome inhibitors and immunomodulatory drugs, along with high-dose chemotherapy and autologous haematopoietic stem cell transplantation, have led to rapid and deep suppression of amyloid light chain production in the majority of patients. However, effective therapies for patients with advanced cardiac involvement are an unmet need. Passive immunotherapies targeting clonal plasma cells and directly accelerating removal of amyloid deposits promise to further improve the overall outlook of this increasingly treatable disease.

Leukocyte Cell-Derived Chemotaxin 2-Associated Renal Amyloidosis: A Case Report

Amyloidosis is a disorder characterized by the deposition of abnormal protein fibrils in tissues. Leukocyte cell-derived chemotaxin 2-associated amyloidosis is a recently recognized entity and is characterized by a distinctive clinicopathologic type of amyloid deposition manifested in adults by varying degrees of impaired kidney function and proteinuria. There are only a limited number of cases reported in the literature. We present a 64-year-old Hispanic female with a history of hypertension who was referred for chronic kidney disease management. The review of her laboratory tests revealed a serum creatinine of 1.5–1.8 mg/dL and microalbuminuria (in the presence of a bland urine sediment) in the past year. She denied any history of diabetes, rheumatologic disorders or exposure to intravenous contrast, nonsteroidal anti-inflammatory drugs, herbals, and heavy metals. Serological workup was negative. A renal biopsy showed diffuse infiltration of glomerulus with pale eosinophilic material strongly positive for Congo red stain and a similar eosinophilic material in the interstitium, muscular arteries, and arterioles. Electron microscopy showed marked infiltration of the mesangium, capillary loops, and interstitium with haphazardly arranged fibrillary deposits (9.8 nm thick). Liquid chromatography tandem mass spectrometry confirmed leukocyte cell-derived chemotaxin 2 (LECT2) amyloid deposition. LECT2 amyloidosis (ALECT2) should be suspected in renal biopsy specimens exhibiting extensive and strong mesangial as well as interstitial congophilia. Individuals with LECT2 renal amyloidosis have a varying prognosis. Therapeutic options include supportive measures and consideration of a kidney transplant for those with end-stage renal disease.

Leukocyte Cell-Derived Chemotaxin-2 Amyloidosis (ALECT2) in a Patient With Lung Adenocarcinoma: An Autopsy Report and Literature Review

Amyloidosis caused by deposition of leukocyte cell-derived chemotaxin-2 amyloidosis (ALECT2) is the most recently described form of systemic amyloidosis and has quickly emerged as a common and possibly underdiagnosed cause of slowly declining renal function, particularly in patients of Hispanic ancestry. We describe the autopsy findings in a 70-year-old Hispanic woman who died of metastatic lung adenocarcinoma and was incidentally found to have extensive amyloid deposition in the kidneys, liver, spleen, adrenal glands, small intestine, gallbladder, lungs, bilateral ovaries, and uterus. The type of amyloid was confirmed to be ALECT2 by mass spectrometry. The pattern of amyloid deposition in the kidneys and the liver was typical for what has been described for ALECT2. In addition, a unique pattern of amyloid deposition was observed in spleen, adrenal glands, small intestine, gallbladder, lungs, ovaries, and uterus. The pattern of amyloid deposition in ALECT2 is distinct from amyloid A and amyloid light-chain and needs to be recognized to avoid misdiagnosis as amyloid light-chain or amyloid A amyloidosis. After recognition, an accurate diagnosis by mass spectrometry and/or immunohistochemical staining is essential to guide treatment and avoid toxic therapies.

A Peptide-Fc Opsonin with Pan-Amyloid Reactivity

There is a continuing need for therapeutic interventions for patients with the protein misfolding disorders that result in systemic amyloidosis. Recently, specific antibodies have been employed to treat AL amyloidosis by opsonizing tissue amyloid deposits thereby inducing cell-mediated dissolution and organ improvement. To develop a pan-amyloid therapeutic agent, we have produced an Fc-fusion product incorporating a peptide, p5, which binds many if not all forms of amyloid. This protein, designated Fcp5, expressed in mammalian cells, forms the desired bivalent dimer structure and retains pan-amyloid reactivity similar to the p5 peptide as measured by immunosorbent assays, immunohistochemistry, surface plasmon resonance, and pulldown assays using radioiodinated Fcp5. Additionally, Fcp5 was capable of opsonizing amyloid fibrils in vitro using a pH-sensitive fluorescence assay of phagocytosis. In mice,¹²⁵ I-labeled Fcp5 exhibited an extended serum circulation time, relative to the p5 peptide. It specifically bound AA amyloid deposits in diseased mice, as evidenced by biodistribution and microautoradiographic methods, which coincided with an increase in active, Iba-1-positive macrophages in the liver at 48 h postinjection of Fcp5. In healthy mice, no specific tissue accumulation was observed. The data indicate that polybasic, pan-amyloid-targeting peptides, in the context of an Fc fusion, can yield amyloid reactive, opsonizing reagents that may serve as next-generation immunotherapeutics.

Amyloidosis: Insights from Proteomics

Amyloidoses are a spectrum of disorders caused by abnormal folding and extracellular deposition of proteins. The deposits lead to tissue damage and organ dysfunction, particularly in the heart, kidneys, and nerves. There are at least 30 different proteins that can cause amyloidosis. The clinical management depends entirely on the type of protein deposited, and thus on the underlying pathogenesis, and often requires high-risk therapeutic intervention. Application of mass spectrometry-based proteomic technologies for analysis of amyloid plaques has transformed the way amyloidosis is diagnosed and classified. Proteomic assays have been extensively used for clinical management of patients with amyloidosis, providing unprecedented diagnostic and biological information. They have shed light on the pathogenesis of different amyloid types and have led to identification of numerous new amyloid types, including ALECT2 amyloidosis, which is now recognized as one of the most common causes of systemic amyloidosis in North America.