Amyloid Typing by Mass Spectrometry in Clinical Practice: a Comprehensive Review of 16,175 Samples

Adding intrinsically disordered proteins to biological ageing clocks

Research into how the young and old differ, and which biomarkers reflect the diverse biological processes underlying ageing, is a current and fast-growing field. Biological clocks provide a means to evaluate whether a molecule, cell, tissue or even an entire organism is old or young. Here we summarize established and emerging molecular clocks as timepieces. We emphasize that intrinsically disordered proteins (IDPs) tend to transform into a β-sheet-rich aggregated state and accumulate in non-dividing or slowly dividing cells as they age. We hypothesize that understanding these protein-based molecular ageing mechanisms might provide a conceptual pathway to determining a cell's health age by probing the aggregation state of IDPs, which we term the IDP clock.

Spatial resolution of renal amyloid deposits through MALDI-MSI: a combined digital and molecular approach to monoclonal gammopathies

AIMS

Identification and characterisation of monoclonal gammopathies of renal significance (MGRS) is critical for therapeutic purposes. Amyloidosis represents one of the most common forms of MGRS, and renal biopsy remains the gold standard for their classification, although mass spectrometry has shown greater sensitivity in this area.

METHODS

In the present study, a new in situ proteomic technique, matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI), is investigated as an alternative to conventional laser capture microdissection MS for the characterisation of amyloids. MALDI-MSI was performed on 16 cases (3 lambda light chain amyloidosis (AL), 3 AL kappa, 3 serum amyloid A amyloidosis (SAA), 2 lambda light chain deposition disease (LCDD), 2 challenging amyloid cases and 3 controls). Analysis began with regions of interest labelled by the pathologist, and then automatic segmentation was performed.

RESULTS

MALDI-MSI correctly identified and typed cases with known amyloid type (AL kappa, AL lambda and SAA). A 'restricted fingerprint' for amyloid detection composed of apolipoprotein E, serum amyloid protein and apolipoprotein A1 showed the best automatic segmentation performance (area under the curve >0.7).

CONCLUSIONS

MALDI-MSI correctly assigned minimal/challenging cases of amyloidosis to the correct type (AL lambda) and identified lambda light chains in LCDD cases, highlighting the promising role of MALDI-MSI for amyloid typing.

How Artificial Intelligence Can Enhance the Diagnosis of Cardiac Amyloidosis: A Review of Recent Advances and Challenges

Cardiac amyloidosis (CA) is an underdiagnosed form of infiltrative cardiomyopathy caused by abnormal amyloid fibrils deposited extracellularly in the myocardium and cardiac structures. There can be high variability in its clinical manifestations, and diagnosing CA requires expertise and often thorough evaluation; as such, the diagnosis of CA can be challenging and is often delayed. The application of artificial intelligence (AI) to different diagnostic modalities is rapidly expanding and transforming cardiovascular medicine. Advanced AI methods such as deep-learning convolutional neural networks (CNNs) may enhance the diagnostic process for CA by identifying patients at higher risk and potentially expediting the diagnosis of CA. In this review, we summarize the current state of AI applications to different diagnostic modalities used for the evaluation of CA, including their diagnostic and prognostic potential, and current challenges and limitations.

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.

2024 Australia-New Zealand Expert Consensus Statement on Cardiac Amyloidosis

Over the past 5 years, early diagnosis of and new treatments for cardiac amyloidosis (CA) have emerged that hold promise for early intervention. These include non-invasive diagnostic tests and disease modifying therapies. Recently, CA has been one of the first types of cardiomyopathy to be treated with gene editing techniques. Although these therapies are not yet widely available to patients in Australia and New Zealand, this may change in the near future. Given the rapid pace with which this field is evolving, it is important to view these advances within the Australian and New Zealand context. This Consensus Statement aims to update the Australian and New Zealand general physician and cardiologist with regards to the diagnosis, investigations, and management of CA.

Clinicopathological characteristics and prognosis in patients with monoclonal gammopathy and renal damage in central China: a multicenter retrospective cohort study

Renal involvement is common in monoclonal gammopathy (MG); however, the same patient may have both MG and non-paraprotein-associated renal damage. Accordingly, distinguishing the cause of renal damage is necessary because of the different clinical characteristics and associated treatments. In this multicenter retrospective cohort study, we described the clinicopathological characteristics and prognosis of 703 patients with MG and renal damage in central China. Patients were classified as having MG of renal significance (MGRS), MG of undetermined significance (MGUS), or hematological malignancy. 260 (36.98%), 259 (36.84%), and 184 (26.17%) had MGRS, MGUS, and hematological malignancies, respectively. Amyloidosis was the leading pattern of MGRS (74.23%), followed by thrombotic microangiopathy (8.85%) and monoclonal immunoglobulin deposition disease (8.46%). Membranous nephropathy was the leading diagnosis of MGUS (39.38%). Renal pathological findings of patients with hematological malignancies included paraprotein-associated lesions (84.78%) and non-paraprotein-associated lesions (15.22%). The presence of nephrotic syndrome and an abnormal free light chain (FLC) ratio were independently associated with MGRS. The overall survival was better in patients with MGUS than in those with MGRS or hematological malignancies.

Truncation of the constant domain drives amyloid formation by immunoglobulin light chains

AL amyloidosis is a life-threatening disease caused by deposition of immunoglobulin light chains. While the mechanisms underlying light chains amyloidogenesis in vivo remain unclear, several studies have highlighted the role that tissue environment and structural amyloidogenicity of individual light chains have in the disease pathogenesis. AL natural deposits contain both full-length light chains and fragments encompassing the variable domain (VL) as well as different length segments of the constant region (CL), thus highlighting the relevance that proteolysis may have in the fibrillogenesis pathway. Here, we investigate the role of major truncated species of the disease-associated AL55 light chain that were previously identified in natural deposits. Specifically, we study structure, molecular dynamics, thermal stability, and capacity to form fibrils of a fragment containing both the VL and part of the CL (133-AL55), in comparison with the full-length protein and its variable domain alone, under shear stress and physiological conditions. Whereas the full-length light chain forms exclusively amorphous aggregates, both fragments generate fibrils, although, with different kinetics, aggregate structure, and interplay with the unfragmented protein. More specifically, the VL-CL 133-AL55 fragment entirely converts into amyloid fibrils microscopically and spectroscopically similar to their ex vivo counterpart and increases the amorphous aggregation of full-length AL55. Overall, our data support the idea that light chain structure and proteolysis are both relevant for amyloidogenesis in vivo and provide a novel biocompatible model of light chain fibrillogenesis suitable for future mechanistic studies.

2024 Update on Classification, Etiology, and Typing of Renal Amyloidosis

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 (AA), transthyretin (ATTR), apolipoprotein AIV (ApoAIV), and beta-2-macroglobulin (AB2m)) 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 paper will review amyloids that involve the kidney and how they are typed.

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.

Cardiac Amyloidosis Due to Transthyretin Protein: A Review

Importance

Systemic amyloidosis from transthyretin (ATTR) protein is the most common type of amyloidosis that causes cardiomyopathy.

Observations

Transthyretin (TTR) protein transports thyroxine (thyroid hormone) and retinol (vitamin A) and is synthesized predominantly by the liver. When the TTR protein misfolds, it can form amyloid fibrils that deposit in the heart causing heart failure, heart conduction block, or arrhythmia such as atrial fibrillation. The biological processes by which amyloid fibrils form are incompletely understood but are associated with aging and, in some patients, affected by inherited variants in the TTR genetic sequence. ATTR amyloidosis results from misfolded TTR protein deposition. ATTR can occur in association with normal TTR genetic sequence (wild-type ATTR) or with abnormal TTR genetic sequence (variant ATTR). Wild-type ATTR primarily manifests as cardiomyopathy while ATTR due to a genetic variant manifests as cardiomyopathy and/or polyneuropathy. Approximately 50 000 to 150 000 people in the US have heart failure due to ATTR amyloidosis. Without treatment, heart failure due to ATTR amyloidosis is associated with a median survival of approximately 5 years. More than 130 different inherited genetic variants in TTR exist. The most common genetic variant is Val122Ile (pV142I), an allele with an origin in West African countries, that is present in 3.4% of African American individuals in the US or approximately 1.5 million persons. The diagnosis can be made using serum free light chain assay and immunofixation electrophoresis to exclude light chain amyloidosis combined with cardiac nuclear scintigraphy to detect radiotracer uptake in a pattern consistent with amyloidosis. Loop diuretics, such as furosemide, torsemide, and bumetanide, are the primary treatment for fluid overload and symptomatic relief of patients with ATTR heart failure. An ATTR-directed therapy that inhibited misfolding of the TTR protein (tafamidis, a protein stabilizer), compared with placebo, reduced mortality from 42.9% to 29.5%, reduced hospitalizations from 0.7/year to 0.48/year, and was most effective when administered early in disease course.

Conclusions and Relevance

ATTR amyloidosis causes cardiomyopathy in up to approximately 150 000 people in the US and tafamidis is the only currently approved therapy. Tafamidis slowed progression of ATTR amyloidosis and improved survival and prevented hospitalization, compared with placebo, in people with ATTR-associated cardiomyopathy.

A proteomic atlas of kidney amyloidosis provides insights into disease pathogenesis

The mechanisms of tissue damage in kidney amyloidosis are not well described. To investigate this further, we used laser microdissection-mass spectrometry to identify proteins deposited in amyloid plaques (expanded proteome) and proteins overexpressed in plaques compared to controls (plaque-specific proteome). This study encompassed 2650 cases of amyloidosis due to light chain (AL), heavy chain (AH), leukocyte chemotactic factor-2-type (ALECT2), secondary (AA), fibrinogen (AFib), apo AIV (AApoAIV), apo CII (AApoCII) and 14 normal/disease controls. We found that AFib, AA, and AApoCII have the most distinct proteomes predominantly driven by increased complement pathway proteins. Clustering of cases based on the expanded proteome identified two ALECT2 and seven AL subtypes. The main differences within the AL and ALECT2 subtypes were driven by complement proteins and, for AL only, 14-3-3 family proteins (a family of structurally similar phospho-binding proteins that regulate major cellular functions) widely implicated in kidney tissue dysfunction. The kidney AL plaque-specific proteome consisted of 24 proteins, including those implicated in kidney damage (α1 antitrypsin and heat shock protein β1). Hierarchical clustering of AL cases based on their plaque-specific proteome identified four clusters, of which one was associated with improved kidney survival and was characterized by higher overall proteomic content and 14-3-3 proteins but lower levels of light chains and most signature proteins. Thus, our results suggest that there is significant heterogeneity across and within amyloid types, driven predominantly by complement proteins, and that the plaque protein burden does not correlate with amyloid toxicity.

A Qualitative Method to Detect Paraproteins from Serum Using Ultra Performance Liquid Chromatography Electrospray Triple Quadrupole Mass Spectrometry

BACKGROUND

Mass spectrometry-based techniques are increasingly reported in the literature for identifying paraproteins due to their improved specificity and sensitivity. The present study demonstrates the capability of ultra performance liquid chromatography (UPLC) electrospray ionization triple quadrupole mass spectrometry for the qualitative analysis of paraproteins.

METHODS

Paraproteins from patient serum (n = 40) were immunopurified using agarose beads coated with camelid antibodies that are specific for various subtypes of immunoglobulins (Igs; G, A, M, and light chains κ, λ). The extracted Igs are reduced to separate light chains from heavy chains in solution. The reduced sample was subjected to UPLC and mass measured using electrospray ionization-mass spectrometry. The mass spectral peaks at specific retention times were deconvoluted after clean-up to obtain the mass of light chains. The interpretation of liquid chromatography peaks and LC-MS data was validated by comparing them with immunofixation electrophoresis (IFE) results.

RESULTS

The interpretation from the chromatographic pattern had a 92.5% (37/40) agreement when compared with mass information. The correlation of mass spectrometry data to IFE was 90% (36/40). The high mass of light chains (>25 kDa) was suggestive of glycosylation. Patient sera positive for IgGκ on IFE (n = 15) were analyzed for the interference of tAbs. The mass of Daratumumab observed in a sample was confirmed by the treating physician. A biclonal of same isotype (IgGκ) was identified.

CONCLUSIONS

The feasibility of using liquid chromatography triple quadrupole mass spectrometry for the identification of the subtype of paraproteins has been demonstrated. The method's applicability to screen for interference from tAbs and identification of biclonals of the same isotype has been highlighted.

The journey towards clinical adoption of MALDI-MS-based imaging proteomics: from current challenges to future expectations

Among the spatial omics techniques available, mass spectrometry imaging (MSI) represents one of the most promising owing to its capability to map the distribution of hundreds of peptides and proteins, as well as other classes of biomolecules, within a complex sample background in a multiplexed and relatively high-throughput manner. In particular, matrix-assisted laser desorption/ionisation (MALDI-MSI) has come to the fore and established itself as the most widely used technique in clinical research. However, the march of this technique towards clinical utility has been hindered by issues related to method reproducibility, appropriate biocomputational tools, and data storage. Notwithstanding these challenges, significant progress has been achieved in recent years regarding multiple facets of the technology and has rendered it more suitable for a possible clinical role. As such, there is now more robust and extensive evidence to suggest that the technology has the potential to support clinical decision-making processes under appropriate circumstances. In this review, we will discuss some of the recent developments that have facilitated this progress and outline some of the more promising clinical proteomics applications which have been developed with a clear goal towards implementation in mind.

Amino acid sequence homology of monoclonal serum free light chain dimers and tissue deposited light chains in AL amyloidosis: a pilot study

OBJECTIVES

Diagnosis of light chain amyloidosis (AL) requires demonstration of amyloid deposits in a tissue biopsy followed by appropriate typing. Previous studies demonstrated increased dimerization of monoclonal serum free light chains (FLCs) as a pathological feature of AL. To further examine the pathogenicity of FLC, we aimed at testing amino acid sequence homology between circulating and deposited light chains (LCs).

METHODS

Matched tissue biopsy and serum of 10 AL patients were subjected to tissue proteomic amyloid typing and nephelometric FLC assay, respectively. Serum FLC monomers (M) and dimers (D) were analyzed by Western blotting (WB) and mass spectrometry (MS).

RESULTS

WB of serum FLCs showed predominance of either κ or λ type, in agreement with the nephelometric assay data. Abnormal FLC M-D patterns typical of AL amyloidosis were demonstrated in 8 AL-λ patients and in one of two AL-κ patients: increased levels of monoclonal FLC dimers, high D/M ratio values of involved FLCs, and high ratios of involved to uninvolved dimeric FLCs. MS of serum FLC dimers showed predominant constant domain sequences, in concordance with the tissue proteomic amyloid typing. Most importantly, variable domain sequence homology between circulating and deposited LC species was demonstrated, mainly in AL-λ cases.

CONCLUSIONS

This is the first study to demonstrate homology between circulating FLCs and tissue-deposited LCs in AL-λ amyloidosis. The applied methodology can facilitate studying the pathogenicity of circulating FLC dimers in AL amyloidosis. The study also highlights the potential of FLC monomer and dimer analysis as a non-invasive screening tool for this disease.

Rare c.302C>T TTR Variant Associated with Transthyretin Amyloidosis

Background and Objectives: Hereditary transthyretin amyloidosis (ATTRv) is a rare disease caused by pathogenic variants in the transthyretin (TTR) gene. More than 140 different disease-causing variants in TTR have been reported. Only a few individuals with a rare TTR variant, c.302C>T, p.(Ala101Val) (historically known as p.(Ala81Val)), primarily associated with cardiac ATTRv, have been described. Therefore, our aim was to analyze the clinical characteristics of individuals with the identified c.302C>T TTR variant at our center. Materials and Methods: We analyzed data from individuals with ATTRv who were diagnosed and treated at Vilnius University Hospital Santaros Klinikos. ATTRv was confirmed by negative hematological analysis for monoclonal protein, positive tissue biopsy or bone scintigraphy and a pathogenic TTR variant. Results: During 2018-2021, the TTR NM_000371.3:c.302C>T, NP_000362.1:p.(Ala101Val) variant was found in one individual in a homozygous state and in three individuals in a heterozygous state. The age of onset of symptoms ranged from 44 to 74 years. The earliest onset of symptoms was in the individual with the homozygous variant. A history of carpal tunnel syndrome was identified in two individuals. On ECG, three individuals had low QRS voltage in limb leads. All individuals had elevated NT-proBNP and hsTroponine I levels on baseline laboratory tests and concentric left ventricular hypertrophy on transthoracic echocardiography. The individual with the homozygous c.302C>T TTR variant had the most pronounced polyneuropathy with tetraparesis. Other patients with the heterozygous variant had more significant amyloid cardiomyopathy. When screening family members, the c.302C>T TTR variant was identified in two phenotypically negative relatives at the ages of 33 and 47 years. Conclusions: c.302C>T is a rare TTR variant associated with ATTRv cardiomyopathy. The homozygous state of this variant was not reported before, and is associated with earlier disease onset and neurological involvement compared to the heterozygote state.

From Patterns to Proteins: Mass Spectrometry Comes of Age in Glomerular Disease

Laser capture microdissection and mass spectrometry (LCM/MS) is a technique that involves dissection of glomeruli from paraffin-embedded biopsy tissue, followed by digestion of the dissected glomerular proteins by trypsin, and subsequently mass spectrometry to identify and semiquantitate the glomerular proteins. LCM/MS has played a crucial role in the identification of novel types of amyloidosis, biomarker discovery in fibrillary GN, and more recently discovery of novel target antigens in membranous nephropathy (MN). In addition, LCM/MS has also confirmed the role for complement proteins in glomerular diseases, including C3 glomerulopathy. LCM/MS is now widely used as a clinical test and considered the gold standard for diagnosis and typing amyloidosis. For the remaining glomerular diseases, LCM/MS has remained a research tool. In this review, we discuss the usefulness of LCM/MS in other glomerular diseases, particularly MN, deposition diseases, and diseases of complement pathways, and advocate more routine use of LCM/MS at the present time in at least certain diseases, such as MN, for target antigen detection. We also discuss the limitations of LCM/MS, particularly the difficulties faced from moving from a research-based technique to a clinical test. Nonetheless, the role of LCM/MS in glomerular diseases is expanding. Currently, LCM/MS may be used to identify the etiology in certain glomerular diseases, but in the future, LCM/MS can play a valuable role in determining pathways of complement activation, inflammation, and fibrosis.

Emerging Role of Scintigraphy Using Bone-Seeking Tracers for Diagnosis of Cardiac Amyloidosis: AJR Expert Panel Narrative Review

Amyloidoses are a complex group of clinical diseases that result from progressive organ dysfunction due to extracellular protein misfolding and deposition. The two most common types of cardiac amyloidosis are transthyretin amyloidosis (ATTR) and light-chain (AL) amyloidosis. Diagnosis of ATTR cardiomyopathy (ATTR-CM) is challenging owing to its phenotypic similarity to other more common cardiac conditions, the perceived rarity of the disease, and unfamiliarity with its diagnostic algorithms; endomyocardial biopsy was historically required for diagnosis. However, myocardial scintigraphy using bone-seeking tracers has shown high accuracy for detection of ATTR-CM and has become a key noninvasive diagnostic test for the condition, receiving support from professional society guidelines and transforming prior diagnostic paradigms. This AJR Expert Panel Narrative Review describes the role of myocardial scintigraphy using bone-seeking tracers in the diagnosis of ATTR-CM. The article summarizes available tracers, acquisition techniques, interpretation and reporting considerations, diagnostic pitfalls, and gaps in the current literature. The critical need for monoclonal testing of patients with positive scintigraphy results to differentiate ATTR-CM from AL cardiac amyloidosis is highlighted. Recent updates in guideline recommendations that emphasize the importance of a qualitative visual assessment are also discussed.

Transthyretin Cardiac Amyloidosis Disguised as Light Chain Amyloidosis or Multiple Myeloma?

We describe 2 challenging cases of cardiac transthyretin amyloidosis initially treated as cardiac amyloidosis light chain in the setting of active myeloma. Endomyocardial biopsy with mass spectrometry was essential to confirm the appropriate diagnosis to direct the treatment.

Amyloid consults do not have to be vexing

Diagnosing amyloidosis can be challenging due to its clinical heterogeneity, need for multiple specialists to make a diagnosis, and lack of a single diagnostic test for the disease. Patients are often diagnosed late, in advanced stage, and after exhibiting multiple symptoms and signs for a long period. It is important to develop a clinical suspicion of amyloidosis, particularly in those with multisystemic symptoms and high-risk patient populations such as those with precursor hematologic conditions. A systematic approach to the workup of suspected amyloidosis is key, including a comprehensive clinical assessment, laboratory tests to assess organ involvement, advanced imaging studies, screening for plasma cell disorder, and tissue biopsy when necessary. After making a diagnosis of amyloidosis, accurate typing of amyloid deposits, differentiating between localized and systemic amyloidosis, and appropriately staging the disease is important. Early diagnosis is crucial for improving patient outcomes and quality of life in light chain amyloidosis.

Identification of amyloidosis of the urinary tract and prostate: Opportunities for early diagnosis & intervention in systemic disease

OBJECTIVES

To determine the prevalence of different amyloid types and frequency of associated systemic amyloidosis in the urinary tract/prostate.

METHODS

We studied Congo red-positive prostate (n = 150) and urinary tract (n = 767) specimens typed by a proteomics-based method between 2008 and 2020. Clinical follow up was available for a subset (urinary tract, n = 111; prostate, n = 17). Amyloid types were correlated with various clinicopathologic features. For patients with clinical follow up, chart review was performed to establish localized versus systemic disease, frequency of initial diagnosis of amyloidosis on urinary tract/prostate specimens, presence of cardiac disease, and death from disease-related complications.

RESULTS

The most common amyloid types were AL/AH in urinary tract (479/767, 62 %) and localized ASem1 in prostate (64/150, 43 %). Urinary tract AL/AH amyloid was usually localized, but systemic AL amyloidosis occurred in both sites (urinary tract: 5/71, 7 %; prostate: 2/2, 100 %). ATTR amyloidosis was seen in over a third of cases (urinary tract: 286/767, 37 %; prostate: 55/150, 37 %). Urinary tract/prostate was the site of the initial ATTR amyloidosis diagnosis in 44/48 patients (92 %), and 38/48 (79 %) were subsequently found to have cardiac involvement. Seminal vesicle/ejaculatory duct involvement was pathognomonic for ASem1-type amyloidosis (39/39, 100 %).

CONCLUSIONS

Over 40 % of patients had systemic amyloidosis, with urinary tract/prostate often the first site in which amyloid was identified. Since early recognition of systemic amyloidosis is critical for optimal patient outcomes, there should be a low threshold to perform Congo red stain. Proteomics-based amyloid typing is recommended since treatment depends on correctly identifying the amyloid type.

Congo Red Staining in Digital Pathology: The Streamlined Pipeline for Amyloid Detection Through Congo Red Fluorescence Digital Analysis

Renal amyloidosis is a rare condition caused by the progressive accumulation of misfolded proteins within glomeruli, vessels, and interstitium, causing functional decline and requiring prompt treatment due to its significant morbidity and mortality. Congo red (CR) stain on renal biopsy samples is the gold standard for diagnosis, but the need for polarized light is limiting the digitization of this nephropathology field. This study explores the feasibility and reliability of CR fluorescence on virtual slides (CRFvs) in evaluating the diagnostic accuracy and proposing an automated digital pipeline for its assessment. Whole-slide images from 154 renal biopsies with CR were scanned through a Texas red fluorescence filter (NanoZoomer S60, Hamamatsu) at the digital Nephropathology Center of the Istituto di Ricovero e Cura a Carattere Scientifico San Gerardo, Monza, Italy, and evaluated double-blinded for the detection and quantification through the amyloid score and a custom ImageJ pipeline was built to automatically detect amyloid-containing regions. Interobserver agreement for CRFvs was optimal (k = 0.90; 95% CI, 0.81-0.98), with even better concordance when consensus-based CRFvs evaluation was compared to the standard CR birefringence (BR) (k = 0.98; 95% CI, 0.93-1). Excellent performance was achieved in the assessment of amyloid score overall by CRFvs (weighted k = 0.70; 95% CI, 0.08-1), especially within the interstitium (weighted k = 0.60; 95% CI, 0.35-0.84), overcoming the misinterpretation of interstitial and capsular collagen BR. The application of an automated digital pathology pipeline (Streamlined Pipeline for Amyloid detection through CR fluorescence Digital Analysis, SPADA) further increased the performance of pathologists, leading to a complete concordance with the standard BR. This study represents an initial step in the validation of CRFvs, demonstrating its general reliability in a digital nephropathology center. The computational method used in this study has the potential to facilitate the integration of spatial omics and artificial intelligence tools for the diagnosis of amyloidosis, streamlining its detection process.

Cardiac Amyloid Detection by PET/CT Imaging of Iodine (124I) Evuzamitide (124I-p5+14): A Phase 1/2 Study

BACKGROUND

The noninvasive detection of cardiac amyloid, as well as deposits in other vital organs, is critical for early diagnosis and quantitative disease monitoring. Positron emission tomography is an intrinsically quantitative imaging modality suitable for high-resolution amyloid detection.

OBJECTIVES

This study sought to evaluate the safety and efficacy of a novel amyloid-reactive peptide, designated p5+14, labeled with iodine-124 (124I), in patients with diverse types of systemic amyloidosis.

METHODS

In a single-site, open label phase 1/2 study (NCT03678259), the safety, biodistribution, and sensitivity of a single intravenous infusion of 124I-evuzamitide was assessed in patients with systemic amyloidosis (n = 50), asymptomatic transthyretin sequence variant carriers (n = 2), and healthy volunteers (n = 5). Subjects were administered 1.4 ± 0.2 mg of 124I-evuzamitide (71.5 ± 12.4 MBq) and positron emission tomography/x-ray computed tomography images acquired at 5.2 hours (Q25-Q75: 4.9-5.4 hours) postinfusion. Images were assessed visually and semi-quantitatively for positive uptake of radiotracer in the heart and other major organs.

RESULTS

Uptake of 124I-evuzamitide in the heart and other abdominothoracic organs was consistent with the patient's clinical presentation and the type of amyloidosis. The patient- and cardiac-associated sensitivity for imaging and clinical observations was 93.6% (95% CI: 82.8%-97.8%) and 96.2% (95% CI: 81.8%-99.8%), respectively. Semi-quantitative uptake of the radiotracer correlated significantly with serum N-terminal pro-B-type natriuretic peptide measurements in patients with light chain-associated amyloidosis. Cardiac uptake was not observed in any healthy volunteers. The agent was well tolerated, with 1 drug-related adverse event and no deaths.

CONCLUSIONS

124I-evuzamitide is an amyloid-binding radiotracer capable of detecting cardiac amyloid in patients with high sensitivity.

Consensus recommendations on holistic care in hereditary ATTR amyloidosis: an international Delphi survey of patient advocates and multidisciplinary healthcare professionals

BACKGROUND

Hereditary transthyretin-mediated amyloidosis is a rare, progressive and potentially life-limiting multisystem disease, affecting every aspect of a patient's life.

OBJECTIVES

This online international Delphi survey aimed to evolve clinical-patient-led practical guidance, to inspire and encourage a holistic approach to care that is managed in specialist settings by multidisciplinary teams and supported by allied healthcare professionals (HCPs) and patient advocacy groups (PAGs).

DESIGN

A 14-member joint patient advocate-HCP primary panel was convened including representation from PAGs and key clinical specialties (neurology, cardiology, internal medicine, physiotherapy, clinical psychology, dietetics and specialist nursing). Guidance evolved on the care provision needed to support seven core goals: early diagnosis and treatment; disease monitoring and organisation of care; maintenance of physical and mental health; family-centred care and caregiver support; patient-doctor dialogue; access to social support and social networking.

PARTICIPANTS

From June to October 2022, 252 HCPs and 51 PAG representatives from 27 countries were invited to participate in a Delphi survey. Of the 122 respondents who answered at least one survey question, most were HCPs (100, 82%) from specialist centres; the remainder were PAG representatives (22, 18%).

MAIN OUTCOME MEASURE

Both level of agreement and feasibility in practice of each recommendation was tested by two anonymised online Delphi voting rounds.

RESULTS

Based on an a priori threshold for consensus of ≥75% agreement, the clinical-patient community endorsed all but one recommendation. However, only 17/49 (35%) recommendations were identified by most HCPs as a core part of routine care; the remainder (32/49 (65%)) were identified as part of core care by <50% of HCPs respondents, or as largely achievable by 30%-45% of HCPs. By comparison, PAGs recorded lower implementation levels.

CONCLUSIONS

Further consideration is needed on how to evolve multidisciplinary services (supported by allied HCPs and PAGs) to address the complex needs of those affected by this disease.

Gastrointestinal amyloidosis: an often unexpected finding with systemic implications

The gastrointestinal (GI) tract is a common site of amyloidosis, but the incidence, clinicopathologic features, and systemic implications of different types of GI amyloidosis are not well understood. GI amyloid specimens (N = 2511) typed using a proteomics-based method between 2008 and 2021 were identified. Clinical and morphologic features were reviewed in a subset of cases. Twelve amyloid types were identified, including AL (77.9%), ATTR (11.3%), AA (6.6%), AH (1.1%), AApoAIV (1.1%), AEFEMP1 (0.7%), ALys (0.4%), AApoAI (0.4%), ALECT2 (0.2%), Aβ2M (0.1%), AGel (0.1%), and AFib (<0.1%). Amino acid abnormalities indicative of known amyloidogenic mutations were detected in 24.4% ATTR cases. AL, ATTR, and AA types all commonly involved submucosal vessels. They also showed some characteristic patterns of involvement of more superficial anatomic compartments, although there was significant overlap. Common indications for biopsy were diarrhea, GI bleed, abdominal pain, or weight loss. Amyloidosis was usually an unexpected finding, but most AL and ATTR patients were ultimately found to have cardiac involvement (83.5% of AL; 100% of ATTR). Although most GI amyloid is of AL type, over 10% are ATTR, over 5% are AA, and twelve different types were identified in total. GI amyloid is often unexpected but usually signals systemic amyloidosis, thus there should be a low threshold to perform biopsy with Congo red stain in patients with unexplained GI symptoms. Clinical and histologic features are nonspecific, and typing should be performed via a robust method such as proteomics as treatment hinges on correctly identifying the amyloid type.

Proteomic and Clinicopathologic Assessment of Penile Amyloidosis: A Single Institutional Review of 12 Cases

OBJECTIVES

There is a paucity of data on penile amyloidosis. We aimed to assess the frequency of different amyloid types in surgical specimens from the penis involved by amyloidosis and correlate relevant clinicopathologic parameters with proteomic findings.

METHODS

Since 2008, our reference laboratory has performed liquid chromatography/tandem mass spectrometry (LC-MS/MS) for amyloid typing. The institutional pathology archive and reference laboratory database were queried to retrospectively identify all penile surgical pathology specimens with LC-MS/MS results between January 1, 2008, and November 23, 2022. Archived H&E-stained and Congo red-stained sections were re-reviewed.

RESULTS

Twelve cases of penile amyloidosis were identified, which represented 0.35% (n = 3,456) of penile surgical specimens. AL-type amyloid was most frequent (n = 7), followed by keratin-type amyloid (n = 3) and ATTR (transthyretin)-type amyloid (n = 2). AL-type amyloid cases often showed diffuse dermal/lamina propria deposition, whereas all keratin-type amyloid cases were localized to the superficial dermis. Two cases with keratin-type amyloid had concomitant cutaneous findings (penile intraepithelial neoplasia and condyloma).

CONCLUSIONS

This series, the largest to date, demonstrates that penile amyloidosis has a heterogeneous proteomic landscape. To the best of our knowledge, this is the first study describing ATTR (transthyretin)-type penile amyloid.

Proteogenomic analysis of chemo-refractory high-grade serous ovarian cancer

To improve the understanding of chemo-refractory high-grade serous ovarian cancers (HGSOCs), we characterized the proteogenomic landscape of 242 (refractory and sensitive) HGSOCs, representing one discovery and two validation cohorts across two biospecimen types (formalin-fixed paraffin-embedded and frozen). We identified a 64-protein signature that predicts with high specificity a subset of HGSOCs refractory to initial platinum-based therapy and is validated in two independent patient cohorts. We detected significant association between lack of Ch17 loss of heterozygosity (LOH) and chemo-refractoriness. Based on pathway protein expression, we identified 5 clusters of HGSOC, which validated across two independent patient cohorts and patient-derived xenograft (PDX) models. These clusters may represent different mechanisms of refractoriness and implicate putative therapeutic vulnerabilities.

Wild-Type Transthyretin Cardiac Amyloidosis in a Transplanted Heart

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM) is more prevalent than appreciated in the elderly. We present the case of an 88-year-old woman who underwent heart transplantation for ischemic cardiomyopathy and then presented 21 years later with new onset atrial flutter, found on endomyocardial biopsy to have new ATTRwt-CM. (Level of Difficulty: Advanced.).

Don't judge a book by its cover: a case report of apolipoprotein A-IV cardiac amyloidosis

Background

To date, at least 20 different amyloidogenic proteins have been documented. Growing evidence suggests that despite being part of the universal amyloid proteome, apolipoprotein A-IV can be amyloidogenic, accounting for less than 1% of cases.

Case summary

A 75-year-old woman was admitted for paroxysmal nocturnal dyspnoea and intermittent exertional shortness of breath and was found to be in acute heart failure. The patient underwent intravenous diuretic therapy and was discharged after decongestion. She then underwent a battery of outpatient tests to determine aetiology of her heart failure. Cardiac magnetic resonance imaging showed severe concentric left ventricular hypertrophy and diffuse late gadolinium enhancement, concerning for amyloidosis, but serologic evaluation for amyloidogenic light chain (AL) amyloidosis was negative. Tc 99m pyrophosphate (PYP) scan showed Grade 2 uptake at 1 h that was only moderately suggestive of transthyretin (TTR) amyloidosis. She ultimately received a right heart catheterization and endomyocardial biopsy, which showed apolipoprotein A-IV amyloid deposition within Congo red-positive areas of the endomyocardial specimen. The patient continues to report dyspnoea on exertion but has avoided additional heart failure admissions with intensification of her diuretic regimen.

Discussion

In this case, nuclear PYP scan to evaluate for TTR amyloidosis demonstrated focal PYP uptake, but endomyocardial biopsy demonstrated apolipoprotein A-IV deposition without evidence of TTR amyloidosis. Our case increases knowledge of this rare form of amyloidosis, suggests that it may result in false positive nuclear PYP results, and highlights the importance of its evaluation, particularly in circumstances in which investigations do not reveal definitive evidence of AL or TTR amyloidosis.

Increased Diagnostic Specificity of Congo Red Stain for Amyloid: The Potential Role of Texas Red-Filtered Fluorescence Microscopy

CONTEXT.—

The tissue diagnosis of amyloidosis is traditionally suggested by hematoxylin-eosin stain and confirmed by Congo red stain, both examined by routine light microscopy. Both false-positive and false-negative congophilia are well documented, limiting the sensitivity and specificity of the Congo red stain for the diagnosis of amyloidosis. Examination of Congo red-stained tissue by Texas Red-filtered fluorescence microscopy (TRFM) is known to enhance the amyloid-specific congophilia, thus increasing the diagnostic sensitivity.

OBJECTIVE.—

To determine whether TRFM can mitigate the false positivity and thus improve the diagnostic specificity of the Congo red stain.

DESIGN.—

Ninety-two tissue samples were categorized into 3 groups. Group I included 15 samples with tissue deposition of amyloid. Group II consisted of 63 samples in which amorphous eosinophilic structures reminiscent of amyloid were seen on hematoxylin-eosin-stained tissue sections. Group III included 14 samples in which amyloid and amyloid-like tissue were seen side by side. The final diagnosis of presence or absence of amyloidosis in each case was established by clinicopathologic correlation. The congophilic areas in each case were identified by light microscopy. The same areas were then examined by TRFM.

RESULTS.—

TRFM enhanced congophilia, confirming the diagnosis of amyloidosis in all group I cases. Enhancement was not seen in 52 of the 63 group II cases. For group III cases, TRFM enhanced the amyloid-specific congophilia, but not the nonspecific congophilia, in all cases.

CONCLUSIONS.—

TRFM increases the diagnostic yield and specificity of Congo red-stained tissue sections for detection of amyloid.

Amyloid Deposition in the Upper Aerodigestive Tract, A Single Institute Experience

Objectives: The purpose of this study is to evaluate clinical information, laboratory results, and pathologic findings of patients with amyloidosis involving larynx, oral cavity, and pharynx from our institute. Methods: A total of 39 specimens from 28 patients were retrieved from 2000 to 2020. Data collection included clinical presentation, radiographic, laboratory results, and pathologic findings. Results: A total of 12 patients had laryngeal amyloidosis and true vocal cord was the most common location. Protein electrophoresis detected monoclonal protein in 10% (1/10) of patients tested. Two patients had hematopoietic disorder (2/12, 17%) and another patient had a peptide profile consistent with amyloid transthyretin (ATTR) detected by mass spectrometry. Twelve patients showed amyloidosis in the oral cavity with 75% involving the tongue. Monoclonal protein was found in 89% of cases tested. Nine patients (9/12, 75%) had systematic involvement including 6 with hematopoietic malignancy and 3 with biopsy-confirmed systemic light chain amyloidosis. Compared to the laryngeal amyloidosis, amyloid deposition in oral cavity had a significant higher association with systematic disease (P < .01). Pharyngeal amyloidosis was seen in 7 patients. Three of 6 patients tested (3/6, 50%) were found to have biopsy-confirmed hematopoietic malignancy. Conclusions: Laryngeal amyloidosis is mostly a localized disease. Amyloidosis involving oral cavity is associated with significantly higher risk of systematic involvement which warrants a comprehensive laboratory, radiographic, and pathologic workup. There is limited data about pharynx amyloidosis. Oropharynx and hypopharynx amyloidosis appear to be more likely associated with underlying hematologic malignancy compared to nasopharynx involvement.

Clinical characterization and outcomes of a cohort of colombian patients with AL Amyloidosis

Background

Amyloid light chain (AL) amyloidosis is characterized by amyloid fibril deposition derived from monoclonal immunoglobulin light chains, resulting in multiorgan dysfunction. Limited data exist on the clinical features of AL amyloidosis.

Objective

This study aims to describe the clinical characteristics, treatments, and outcomes in Colombian patients with AL amyloidosis.

Methods

A retrospective descriptive study was conducted at three high-complexity centers in Medellín, Colombia. Adults with AL amyloidosis diagnosed between 2012 and 2022 were included. Clinical, laboratory, histological, treatment, and survival data were analyzed.

Results

The study included 63 patients. Renal involvement was most prevalent (66%), followed by cardiac involvement (61%). Multiorgan involvement occurred in 61% of patients. Amyloid deposition was most commonly detected in renal biopsy (40%). Bortezomib-based therapy was used in 68%, and 23.8% received high-dose chemotherapy with autologous hematopoietic stem cell transplantation (HDCT-ASCT). Hematological response was observed in 95% of patients with available data. Cardiac and renal organ responses were 15% and 14%, respectively. Median overall survival was 45.1 months (95% CI: 22.2-63.8). In multivariate analysis, cardiac involvement was significantly associated with inferior overall survival (HR 3.27; 95% CI: 1.23-8.73; p=0.018), HDCT-ASCT had a non-significant trend towards improved overall survival (HR 0.25; 95% CI: 0.06-1.09; p=0.065).

Conclusions

In this study of Colombian patients with AL amyloidosis, renal involvement was more frequent than cardiac involvement. Overall survival and multiorgan involvement were consistent with data from other regions of the world. Multivariate analysis identified cardiac involvement and HDCT-AHCT as possible prognostic factors.

Evaluating the Amyloidosis Speakers Bureau: the influence of amyloidosis patients' narratives on medical students' knowledge, attitudes, and behavioral intent

Background:  Amyloidosis is a complex multi-systemic disease. Lack of knowledge about amyloidosis and subsequent mis- or under-diagnosis are major obstacles to treatment, which result in life-threatening organ damage, morbidity, and mortality. Hence, the purpose of this study is to explore the effectiveness of amyloidosis patients' narratives on medical students. Methods:  The Amyloidosis Speakers Bureau (ASB) arranges for amyloidosis patients to speak about their diagnostic and treatment experiences with medical students. Using a randomized post-test only experiment, we compared the effectiveness of patients' narratives between two groups (treatment and control). Outcome measures included medical students' intent to actively communicate with patients, acquire knowledge about amyloidosis, and reconsider diagnoses when warranted. Results:  The treatment group (those who listened to an ASB patient speaker) had higher mean differences on all measures, including the desire to improve communication with patients, acquire and apply knowledge of amyloidosis, and willingness to reconsider diagnoses when symptoms are puzzling. Conclusions:  ASB patient educators widened awareness of an under-diagnosed disease. Listening to a patient's narrative was associated with positive attitudes toward communication with patients, interest in acquiring and applying knowledge of amyloidosis, and humility about diagnosis. Narrative and persuasion theory are used to explain this quantitative evidence of the power of patient narratives.

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.

Amyloidosis: a case series and review of the literature

BACKGROUND

Systemic amyloidosis is group of disorders characterized by the accumulation of insoluble proteins in tissues. The most common form of systemic amyloidosis is light chain amyloidosis, which results from the accumulation of misfolded immunoglobulins. The disease is progressive, with treatment targeted at the underlying plasma cell dyscrasia. Since essentially any organ system can be affected, the presentation is variable and delays in diagnosis are common. Given this diagnostic difficulty, we discuss four different manifestations of light chain amyloidosis.

CASE PRESENTATIONS

In this case series, we discuss four cases of light chain amyloidosis. These include cardiac, hepatic, and gastrointestinal as well as autonomic and peripheral nerve involvement with amyloidosis. The patients in our series are of Caucasian background and include a  69-year-old female, a 29-year-old female, a 68-year-old male, and a 70-year-old male, respectively. The case discussions highlight variability in presentation and diagnostic challenges.

CONCLUSIONS

Amyloidosis is a rare but serious disease that is often complicated by long delays in diagnosis. Morbidity and mortality can sometimes be limited if diagnosed earlier. We hope our real life cases will contribute to understanding and to early suspicion that can lead to early diagnosis and management.

18F-FDG/13N-ammonia cardiac PET findings in ATTR cardiac amyloidosis

18F-flurodeoxyglycose (FDG)/13N-ammonia positron emission tomography/computed tomography (PET/CT) is frequently utilized to evaluate cardiac sarcoidosis (CS) but findings can reflect other forms of myocardial inflammation or altered myocardial metabolic activity. Herein, we present five cases where cardiac PET findings suggested CS, but right ventricular endomyocardial biopsy samples revealed ATTR-type cardiac amyloidosis.

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.

Precise diagnosis and typing of early-stage renal immunoglobulin-derived amyloidosis by label-free quantification of parallel reaction monitoring-based targeted proteomics

BACKGROUND

Early diagnosis and typing are crucial for improving the prognosis of patients with renal amyloidosis. Currently, Untargeted proteomics based precise diagnosis and typing of amyloid deposits are crucial for guiding patient management. Although untargeted proteomics achieve ultra-high-throughput by selecting the most abundant eluting cationic peptide precursors in series for tandem MS events, it lacks in sensitivity and reproducibility, which may not be suitable for early-stage renal amyloidosis with minor damages. Here, we aimed to develop parallel reaction monitoring (PRM)-based targeted proteomics to achieve high sensitivity and specificity by determining absolute abundances and codetecting all transitions of highly repeatable peptides of preselected amyloid signature and typing proteins in identifying early-stage renal immunoglobulin-derived amyloidosis.

METHODS AND RESULTS

In 10 discovery cohort cases, Congo red-stained FFPE slices were micro-dissected and analyzed by data-dependent acquisition-based untargeted proteomics for preselection of typing specific proteins and peptides. Further, a list of proteolytic peptides from amyloidogenic proteins and internal standard proteins were quantified by PRM-based targeted proteomics to validate performance for diagnosis and typing in 26 validation cohort cases. The diagnosis and typing effectiveness of PRM-based targeted proteomics in 10 early-stage renal amyloid cases was assessed via a comparison with untargeted proteomics. A peptide panel of amyloid signature proteins, immunoglobulin light chain and heave chain in PRM-based targeted proteomics showed significantly distinguishing ability and amyloid typing performance in patients. The diagnostic algorithm of targeted proteomics with a low amount of amyloid deposits in early-stage renal immunoglobulin-derived amyloidosis showed better performance than untargeted proteomics in amyloidosis typing.

CONCLUSIONS

This study demonstrates that the utility of these prioritized peptides in PRM-based targeted proteomics ensure high sensitivity and reliability for identifying early-stage renal amyloidosis. Owing to the development and clinical application of this method, rapid acceleration of the early diagnosis, and typing of renal amyloidosis is expected.

A Comprehensive Multidisciplinary Diagnostic Algorithm for the Early and Efficient Detection of Amyloidosis

Amyloidosis is a rare protein misfolding disease caused by the accumulation of amyloid fibrils in various tissues and organs. There are different subtypes of amyloidosis, with light chain (AL) amyloidosis being the most common. Amyloidosis is notoriously difficult to diagnose because it is clinically heterogeneous, no single test is diagnostic for the disease, and diagnosis typically involves multiple specialists. Here, we propose an integrated, multidisciplinary algorithm for efficiently diagnosing amyloidosis. Drawing on research from several medical disciplines, we have combined clinical decisions and best practices into a comprehensive algorithm to facilitate the early detection of amyloidosis. Currently, many patients are diagnosed more than 6 months after symptom onset, yet early diagnosis is the major predictor of survival. Our algorithm aims to shorten the time to diagnosis with efficient sequencing of tests and minimizing uninformative investigations. We also recommend typing and staging of confirmed amyloidosis to guide treatment. By reducing time to diagnosis, our algorithm could lead to earlier and more targeted treatment, ultimately improving prognosis and survival.

Subtyping of cardiac amyloidosis by mass spectrometry-based proteomics of endomyocardial biopsies

BACKGROUND

Cardiac amyloidosis is a severe condition leading to restrictive cardiomyopathy and heart failure. Mass spectrometry-based methods for cardiac amyloid subtyping have become important diagnostic tools but are currently used only in a few reference laboratories. Such methods include laser-capture microdissection to ensure the specific analysis of amyloid deposits. Here we introduce a direct proteomics-based method for subtyping of cardiac amyloidosis.

METHODS

Endomyocardial biopsies were retrospectively analysed from fresh frozen material of 78 patients with cardiac amyloidosis and from 12 biopsies of unused donor heart explants. Cryostat sections were digested with trypsin and analysed with liquid chromatography - mass spectrometry, and data were evaluated by proteomic software.

RESULTS

With a diagnostic threshold set to 70% for each of the four most common amyloid proteins affecting the heart (LC κ, LC λ, TTR and SAA), 65 of the cases (87%) could be diagnosed, and of these, 61 cases (94%) were in concordance with the original diagnoses. The specimens were also analysed for the summed intensities of the amyloid signature proteins (ApoE, ApoA-IV and SAP). The intensities were significantly higher (p < 0.001) for all assigned cases compared with controls.

CONCLUSION

Cardiac amyloidosis can be successfully subtyped without the prior enrichment of amyloid deposits with laser microdissection.

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.

Diagnostic and Treatment Strategies for AL Amyloidosis in an Era of Therapeutic Innovation

Despite significant progress and improving outcomes in the management of plasma cell disorders, AL amyloidosis remains diagnostically and therapeutically challenging for clinicians across practice settings. There is, however, a reason for optimism with the advent of new combination therapy approaches and novel targets offering the promise of improvement in end organ function, survival, and quality of life. This review offers a clinically applicable overview of an approach to diagnosis, risk stratification, and clinical management of AL amyloidosis in an era of rapid therapeutic innovation.

Diagnostic Challenges and Solutions in Systemic Amyloidosis

Amyloidosis refers to a clinically heterogeneous group of disorders characterized by the extracellular deposition of amyloid proteins in various tissues of the body. To date, 42 different amyloid proteins that originate from normal precursor proteins and are associated with distinct clinical forms of amyloidosis have been described. Identification of the amyloid type is essential in clinical practice, since prognosis and treatment regimens both vary according to the particular amyloid disease. However, typing of amyloid protein is often challenging, especially in the two most common forms of amyloidosis, i.e., the immunoglobulin light chain amyloidosis and transthyretin amyloidosis. Diagnostic methodology is based on tissue examinations as well as on noninvasive techniques including serological and imaging studies. Tissue examinations vary depending on the tissue preparation mode, i.e., whether it is fresh-frozen or fixed, and they can be carried out by ample methodologies including immunohistochemistry, immunofluorescence, immunoelectron microscopy, Western blotting, and proteomic analysis. In this review, we summarize current methodological approaches used for the diagnosis of amyloidosis and discusses their utility, advantages, and limitations. Special attention is paid to the simplicity of the procedures and their availability in clinical diagnostic laboratories. Finally, we describe new methods recently developed by our team to overcome limitations existing in the standard assays used in common practice.

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.

Immunoglobulin Light Chain Amyloidosis: Diagnosis and Risk Assessment

Immunoglobulin light chain (AL) amyloidosis is a clonal plasma cell disorder with multiple clinical presentations. The diagnosis of AL amyloidosis requires a high index of suspicion, making a delay in diagnosis common, which contributes to the high early mortality seen in this disease. Establishing the diagnosis of AL amyloidosis requires the demonstration of tissue deposition of amyloid fibrils. A bone marrow biopsy and fat pad aspirate performed concurrently have a high sensitivity for the diagnosis of AL amyloidosis and negate the need for organ biopsies in most patients. An accurate diagnosis requires amyloid typing via additional testing, including tissue mass spectrometry. Prognostication for AL amyloidosis is largely driven by the organs impacted. Cardiac involvement represents the single most important prognostic marker, and the existing staging systems are driven by cardiac biomarkers. Apart from organ involvement, plasma cell percentage on the bone marrow biopsy, specific fluorescence in situ hybridization findings, age at diagnosis, and performance status are important prognostic markers. This review elaborates on the diagnostic testing and prognostication for patients with newly diagnosed AL amyloidosis.

Proteomic Identification and Clinicopathologic Characterization of Splenic Amyloidosis

The spleen is a commonly encountered specimen in surgical pathology. However, little is known about the incidence, morphologic pattern, and clinical features of spleens involved by amyloidosis. We retrospectively identified 69 spleen amyloid cases typed using a proteomics-based method between 2008 and 2020. The frequency of amyloid types, clinicopathologic features, and distribution of amyloid deposits were assessed. Four amyloid types were detected: immunoglobulin light chain (AL) (N=30; 43.5%); leukocyte chemotactic factor 2 amyloidosis (ALECT2) (N=30; 43.5%); amyloid A (AA) (N=8; 11.6%); and fibrinogen alpha (AFib) (N=1; 1.4%). The splenic amyloid showed 5 distinct distribution patterns: (1) diffuse pattern, exhibited by most AL cases; (2) red pulp pattern, exhibited by most ALECT2 cases; (3) multinodular pattern, seen in subsets of AA and AL-kappa cases; (4) mass-forming pattern, seen in the AFib case; and (5) vascular only, seen in a subset of AA cases. Atraumatic splenic rupture was the most common reason for splenectomy in AL cases, while most ALECT2 spleens were removed incidentally during an unrelated abdominal surgery. Splenomegaly was significantly more common in AA spleens than in AL or ALECT2 spleens and was often the reason for splenectomy in this group. In conclusion, splenic amyloid may be underrecognized as it is often an incidental finding. Although, as expected, many of the spleens were involved by AL amyloidosis, ALECT2 emerged as another common spleen amyloid type. Although the spleen amyloid types exhibited characteristic distribution patterns, proteomics-based typing is warranted as some morphologic overlap still exists. Awareness of ALECT2 as a major spleen amyloid type is important for appropriate diagnostic workup and patient management.