Molecular mechanisms of amyloidosis

Extracellular Volume Fraction by Computed Tomography Predicts Long-Term Prognosis Among Patients With Cardiac Amyloidosis

BACKGROUND

Light chain (AL) and transthyretin (ATTR) amyloid fibrils are deposited in the extracellular space of the myocardium, resulting in heart failure and premature mortality. Extracellular expansion can be quantified by computed tomography, offering a rapid, cheaper, and more practical alternative to cardiac magnetic resonance, especially among patients with cardiac devices or on renal dialysis.

OBJECTIVES

This study sought to investigate the association of extracellular volume fraction by computed tomography (ECV_CT), myocardial remodeling, and mortality in patients with systemic amyloidosis.

METHODS

Patients with confirmed systemic amyloidosis and varying degrees of cardiac involvement underwent electrocardiography-gated cardiac computed tomography. Whole heart and septal ECV_CT was analyzed. All patients also underwent clinical assessment, electrocardiography, echocardiography, serum amyloid protein component, and/or technetium-99m (^99mTc) 3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy. ECV_CT was compared across different extents of cardiac infiltration (ATTR Perugini grade/AL Mayo stage) and evaluated for its association with myocardial remodeling and all-cause mortality.

RESULTS

A total of 72 patients were studied (AL: n = 35, ATTR: n = 37; median age: 67 [IQR: 59-76] years, 70.8% male). Mean septal ECV_CT was 42.7% ± 13.1% and 55.8% ± 10.9% in AL and ATTR amyloidosis, respectively, and correlated with indexed left ventricular mass (r = 0.426; P < 0.001), left ventricular ejection fraction (r = 0.460; P < 0.001), N-terminal pro-B-type natriuretic peptide (r = 0.563; P < 0.001), and high-sensitivity troponin T (r = 0.546; P < 0.001). ECV_CT increased with cardiac amyloid involvement in both AL and ATTR amyloid. Over a mean follow-up of 5.3 ± 2.4 years, 40 deaths occurred (AL: n = 14 [35.0%]; ATTR: n = 26 [65.0%]). Septal ECV_CT was independently associated with all-cause mortality in ATTR (not AL) amyloid after adjustment for age and septal wall thickness (HR: 1.046; 95% CI: 1.003-1.090; P = 0.037).

CONCLUSIONS

Cardiac amyloid burden quantified by ECV_CT is associated with adverse cardiac remodeling as well as all-cause mortality among ATTR amyloid patients. ECV_CT may address the need for better identification and risk stratification of amyloid patients, using a widely accessible imaging modality.

Tissue Characterization in Cardiac Amyloidosis

Cardiac amyloidosis (CA) has long been considered a rare disease, but recent advancements in diagnostic tools have led to a reconsideration of the epidemiology of CA. Amyloid light-chain (AL) and transthyretin (ATTR) amyloidoses are the most common forms of cardiac amyloidosis. Due to the distinct treatments and the different prognoses, amyloid typing is crucial. Although a non-biopsy diagnosis can be obtained in ATTR amyloidosis when certain diagnostic criteria are fulfilled, tissue characterization still represents the gold standard for the diagnosis and typing of CA, particularly in AL amyloidosis. The present review focuses on the status of tissue characterization in cardiac amyloidosis, from histochemistry to immunohistochemistry and mass spectrometry, as well as on its future directions.

Cardiovascular Magnetic Resonance Imaging-Based Right Atrial Strain Analysis of Cardiac Amyloidosis

Background: Cardiac amyloidosis (CA) manifests in a hypertrophic phenotype with a poor prognosis, making differentiation from hypertrophic cardiomyopathy (HCM) challenging and delaying early treatment. The extent to which magnetic resonance imaging (MRI) quantifies the right atrial strain (RAS) and strain rate (RASR), providing valuable diagnostic information, is not yet clinically established. Aims: This study assesses diagnostic differences in the longitudinal RAS and RASR between CA and HCM patients, control subjects (CTRL) and CA subtypes in addition to the impact of atrial fibrillation (AF) on the right atrial function in CA patients. The RAS and RASR of tricuspid regurgitation (TR) patients are used to assess the potential for diagnostic overlap. Methods: RAS and RASR quantification was conducted via MRI feature-tracking for biopsy-confirmed CA patients with subtypes identified. Strain parameters were compared for CTRL, HCM and TR patients. Post hoc testing identified intergroup differences. Results: In total, 41 CA patients were compared to 47 CTRL, 20 HCM and 31 TR patients. Reservoir (R), conduit and booster RAS and RASRs allow for significant differentiation (p < 0.001) between CA and HCM patients (R: 10.6 ± 14.3% vs. R: 33.5 ± 16.3%) and CTRL (R: 44.6 ± 15.7%). Booster and reservoir RAS and RASRs qualified as reliable diagnostic tests (AUC > 0.8). CA patients with AF, in contrast to sinus rhythm, demonstrated a significantly impaired reservoir RAS and RASR and booster RASR. The discriminative power of RAS for CA vs. TR was insufficient (R: 10.6% ± 14.3% vs. 7.0% ± 6.0%, p = 0.069). Differentiation between 21 transthyretin and 20 light-chain amyloidosis subtypes was not achievable (R: 0.7% ± 1.0% vs. 0.7% ± 1.0%, p = 0.827). Conclusion: The MRI-derived RAS and RASR are impaired in CA patients and may support noninvasive differentiation between CA, HCM and CTRL.

IgM-Related Immunoglobulin Light Chain (AL) Amyloidosis

Waldenström macroglobulinemia (WM) is a rare lymphoplasmacytic disorder characterized by an IgM paraprotein. The clinical presentation of WM varies and can include common manifestations such as anemia and hyperviscosity, in addition to less common features such as cryoglobulinemia, IgM-related neuropathy, and immunoglobulin light chain (AL) amyloidosis. Amyloidosis is a protein-folding disorder in which vital organ damage occurs due to the accumulation of misfolded protein aggregates. The most common type of amyloidosis in patients with an IgM paraprotein is AL amyloidosis, although other types of amyloidosis may occur. IgM-related amyloidosis has distinct clinical features when compared with other subtypes of AL amyloidosis. This review highlights the diagnostic criteria of IgM-related AL amyloidosis, as well as the clinical characteristics and treatment options for this disorder.

Localized light chain amyloidosis: A self-limited plasmacytic B-cell lymphoproliferative disorder

Immunoglobulin light chain amyloidosis can be either systemic or localized. Although these conditions share a similar name, they are strikingly different. Localized light chain amyloidosis has been challenging to characterize due to its lower incidence and highly heterogeneous clinical presentation. Here, we review the emerging literature, emphasizing recent reports on large cohorts of patients with localized amyloidosis, and provide insights into this condition's pathology and natural history. We find that patients with localized amyloidosis have an excellent prognosis with overall survival similar to that of the general population. Furthermore, the risk of progression to systemic disease is low and likely represents initial mischaracterization as localized disease. Therefore, we argue for the incorporation of more sensitive techniques to rule out systemic disease at diagnosis. Despite increasing mechanistic understanding of this condition, much remains to be discovered regarding the cellular clonal evolution and the molecular processes that give rise to localized amyloid formation. While localized surgical resection of symptomatic disease is typically the treatment of choice, the presentation of this disease across the spectrum of plasmacytic B-cell lymphoproliferative disorders, and the frequent lack of an identifiable neoplastic clone, can make therapy selection a challenge in the uncommon situation that systemic chemotherapy is required.

Primary Localized Small Bowel Amyloidosis: A Rare Cause of Diarrhea Detected by Balloon-Assisted Enteroscopy

Gastrointestinal involvement occurs in approximately 4% of cases of systemic amyloidosis and may be associated with heterogeneous and nonspecific clinical manifestations and endoscopic findings, which poses important diagnostic challenges. A 76-year-old female with previous medical history of breast cancer, hypertension, dyslipidemia, asthma, and depression presented to emergency department with a 1-month history of diarrhea, abdominal pain, anorexia, asthenia, and weight loss. Physical examination revealed dehydration and abdominal tenderness. Stool microbiologic studies, Clostridium difficile toxin, fecal leukocyte count, stool fat, and celiac serology were all negative. Remarkably, an axillary lymphadenopathy was also noted and its investigation revealed multiple myeloma, which raised suspicion for gastrointestinal amyloidosis. However, upper digestive endoscopy and colonoscopy did not reveal abnormalities and both gastric and colon biopsies were negative for amyloid, as was abdominal fat biopsy. As the patient also presented hypoproteinemia and hypoalbuminemia suggestive of protein-losing enteropathy, videocapsule endoscopy was performed where petechiae, villous atrophy, and fissures were seen along jejunal mucosa. These findings were confirmed with double-balloon enteroscopy and jejunal biopsies revealed extensive deposition of an amorphous hyaline material in lamina propria and muscularis mucosae that exhibited apple-green birefringence under polarized light after Congo red staining, consistent with localized small bowel amyloidosis secondary to multiple myeloma. Chemotherapy was started, but she would die after 3 weeks. This case illustrates the role of balloon-assisted enteroscopy in diagnosis of localized small bowel amyloidosis with jejunal involvement.

AL Amyloidosis for Cardiologists: Awareness, Diagnosis, and Future Prospects: JACC: CardioOncology State-of-the-Art Review

Amyloid light chain (AL) amyloidosis is a rare, debilitating, often fatal disease. Symptoms of cardiomyopathy are common presenting features, and patients often are referred to cardiologists. Cardiac amyloid infiltration is the leading predictor of death. However, the variable presentation and perceived rarity of the disease frequently lead to delay in suspecting amyloidosis as a cause of heart failure, leading to misdiagnoses and a marked delay in diagnosis, with devastating consequences for the patient. A median time from symptom onset to correct diagnosis of about 2 years is often too long when median survival from diagnosis for patients with AL amyloidosis and cardiomyopathy is 4 months to 2 years. The authors highlight the challenges to diagnosis, identify gaps in the current knowledge, and summarize novel treatments on the horizon to raise awareness about the critical need for early recognition of symptoms and diagnosis of AL amyloidosis aimed at accelerating treatment and improving outcomes for patients.

Pulmonary function tests reveal unrecognised lung dysfunction and have independent prognostic significance in patients with systemic AL amyloidosis

BACKGROUND

Lung involvement in AL amyloidosis is not very common, but post-mortem data and retrospective studies suggest it is likely underrecognized.

AIM

To perform a comprehensive evaluation of lung function with pulmonary function tests (PFTs) in patients with newly diagnosed AL amyloidosis.

METHODS

A prospective, non-interventional study of 139 consecutive patients with newly diagnosed AL amyloidosis.

RESULTS

PFTs indicated normal breathing physiology in 68% of patients, obstructive in 9% and restrictive in 23%; the latter was associated with worse survival (28.6 vs 76 months for obstructive/normal physiology, p = 0.002) and remained significant after adjustment for Mayo stage and abnormal chest-CT. Forced vital capacity <80% of predicted value, forced expiratory volume <80% of predicted value, and carbon monoxide diffusion capacity <70% were independently associated with poorer survival. Respiratory muscle strength (as assessed by maximal expiratory (Pe) and inspiratory (Pi) pressure) was affected in most patients (64% had Pi < 55% and 57% had Pe < 70% of predicted values). Pe% was an independent prognostic factor for survival (HR: 0.984 per 1% unit increase, p = 0.007).

CONCLUSIONS

Pulmonary dysfunction, as assessed with PFTs, is common and underrecognized in patients with systemic AL amyloidosis, with significant prognostic and potentially therapeutic implications, independent of the degree of cardiac dysfunction or chest-CT findings.

Noninvasive Diagnostics of Renal Amyloidosis: Current State and Perspectives

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

Alterations of the gut microbiota in patients with immunoglobulin light chain amyloidosis

Background

Emerging evidence revealed that gut microbial dysbiosis is implicated in the development of plasma cell dyscrasias and amyloid deposition diseases, but no data are available on the relationship between gut microbiota and immunoglobulin light chain (AL) amyloidosis.

Methods

To characterize the gut microbiota in patients with AL amyloidosis, we collected fecal samples from patients with AL amyloidosis (n=27) and age-, gender-, and BMI-matched healthy controls (n=27), and conducted 16S rRNA MiSeq sequencing and amplicon sequence variants (ASV)-based analysis.

Results

There were significant differences in gut microbial communities between the two groups. At the phylum level, the abundance of Actinobacteriota and Verrucomicrobiota was significantly higher, while Bacteroidota reduced remarkably in patients with AL amyloidosis. At the genus level, 17 genera, including Bifidobacterium, Akkermansia, and Streptococcus were enriched, while only 4 genera including Faecalibacterium, Tyzzerella, Pseudomonas, and Anaerostignum decreased evidently in patients with AL amyloidosis. Notably, 5 optimal ASV-based microbial markers were identified as the diagnostic model of AL amyloidosis and the AUC value of the train set and the test set was 0.8549 (95% CI 0.7310-0.9789) and 0.8025 (95% CI 0.5771-1), respectively. With a median follow-up of 19.0 months, further subgroup analysis also demonstrated some key gut microbial markers were related to disease severity, treatment response, and even prognosis of patients with AL amyloidosis.

Conclusions

For the first time, we demonstrated the alterations of gut microbiota in AL amyloidosis and successfully established and validated the microbial-based diagnostic model, which boosted more studies about microbe-based strategies for diagnosis and treatment in patients with AL amyloidosis in the future.

Persistent diarrhea with petechial rash - unusual pattern of light chain amyloidosis deposition on skin and gastrointestinal biopsies: A case report

BACKGROUND

Amyloidosis is a rare disease characterized by extracellular deposition of misfolded protein aggregated into insoluble fibrils. Gastrointestinal involvement in systemic amyloidosis is common, but is often subclinical or presents as vague and nonspecific symptoms. It is rare for gastrointestinal symptoms to be the main presenting symptom in patients with systemic amyloidosis, causing it to be undiagnosed until late-stage disease.

CASE SUMMARY

A 53 year-old man with diarrhea, hematochezia, and weight loss presented to a community hospital. Colonoscopy with biopsy at that time was suspicious for Crohn disease. Due to worsening symptoms including nausea, vomiting, and a new petechial rash, an abdominal fat pad biopsy was done. The biopsy showed papillary and adnexal dermal amyloid deposition, in a pattern usually seen with cutaneous amyloidosis. However, Cytokeratin 5/6 was negative, excluding cutaneous amyloidosis. The patterns of nodular amyloidosis, subcutaneous amyloid deposits and perivascular amyloid were not seen. Periodic Acid-Schiff stain was negative for lipoid proteinosis, Congo red was positive for apple green birefringence on polarization and amyloid typing confirmed amyloid light chain amyloidosis. Repeat endoscopic biopsies of the gastrointestinal tract showed amyloid deposition from the esophagus to the rectum, in a pattern usually seen in serum amyloid A in the setting of chronic inflammatory diseases, including severe inflammatory bowel disease. Bone marrow biopsy showed kappa-restricted plasma cell neoplasm.

CONCLUSION

Described is an unusual presentation of primary systemic amyloidosis, highlighting the risk of misdiagnosis with subsequent significant organ dysfunction and high mortality.

Presentation of Sjogren Syndrome as Nodular Pulmonary Amyloidosis

Sjogren syndrome is an autoimmune disorder that leads to dryness in the eyes and mouth. Nodular pulmonary amyloidosis is a localized amyloid deposition pathology commonly seen with monoclonal lymphoproliferative disorders. We present a patient who came in with dyspnea and was found to have nodular pulmonary amyloidosis on biopsy. Commonly associated lymphoproliferative pathologies were ruled out and on further workup, the patient was found to have Sjogren syndrome. This case demonstrates pulmonary nodular amyloidosis as a rare presentation of Sjogren syndrome in the setting of relatively well-controlled symptoms. Detection of pulmonary nodular amyloidosis should prompt evaluation of associated conditions such as malignancy and autoimmune disorders to guide further management.

Amyloid Deposits in a Functionally Unicuspid Stenotic Aortic Valve

Amyloidosis concomitant to aortic stenosis usually occurs with myocardial infiltration by the transthyretin protein. To our knowledge, this is the first report of localized amyloidosis of indeterminate type in a severely calcified and functionally unicuspid aortic valve. Isolated dystrophic valvular amyloidosis is believed to be related to fibrocalcific valve disease. In light of the literature on this topic, the present case raises new hypotheses on pathophysiology and further supports the contributory role of unusual non-tricuspid valve morphology in the development of dystrophic amyloid, likely secondary to altered hemodynamic stress.

Cardiac AL amyloidosis presenting as recurrent dyspnoea in a patient with cancer: an important clinical clue to an early diagnosis

Cardiac amyloidosis (CA) is challenging to diagnose due to its non-specific clinical manifestations early in the disease process. We report the case of a patient who presented with dyspnoea, abdominal distension and leg swelling. Medical history was notable for hypertension, recurrent vulvar squamous cell carcinoma and polysubstance abuse. Over 1 year before the official diagnosis of CA, the patient had multiple hospital readmissions for dyspnoea. Our case illustrates the importance of having a high index of clinical suspicion for an early diagnosis of CA. Furthermore, it highlights the need to re-evaluate a presumed diagnosis when a patient's symptoms recur or do not respond to appropriate treatment and to consider the influence of social factors on diagnostic processes.

Targeting Amyloid Fibrils by Passive Immunotherapy in Systemic Amyloidosis

Systemic amyloidoses are characterized by the unrelenting deposition of autologous proteins as highly ordered fibrils in target organs. The ensuing, potentially fatal organ dysfunction is the result of the combined damage caused by the proteotoxic effect of prefibrillar species and by the cytotoxicity and the structural alterations produced by the amyloid fibrils. Current therapy is focused on eliminating the amyloid protein, thus extinguishing the amyloid cascade at its origin. While this approach may end the cell damage caused by prefibrillar aggregates and prevent further amyloid accumulation, the noxious effects of the amyloid fibrils persist and may hamper the recovery of organ function, which is the ultimate goal of therapy as it is necessary to improve the quality of life and extend survival. Preclinical studies indicate that the clearance of amyloid deposits can be accelerated by specific antibodies targeting amyloid fibrils that activate complement-mediated macrophages and giant cell phagocytosis, possibly promoting the recovery of organ function. Measuring the therapeutic effect of anti-amyloid agents is still a matter of research. In recent years, several monoclonal antibodies targeting amyloid deposits have been tested in clinical trials with mixed outcomes. Recent encouraging results from phase I/II trials, new anti-amyloid agents, and new antibody engineering offer hope that effective amyloid removal will be accomplished in the near future, accelerating organ recovery and improving quality of life and survival.

Amyloidosis and COVID-19: experience from an amyloid program in Canada

Severe acute respiratory syndrome coronavirus (SARS-CoV2) and associated COVID-19 infection continue to impact patients globally. Patients with underlying health conditions are at heightened risk of adverse outcomes from COVID-19; however, research involving patients with rare health conditions remains scarce. The amyloidoses are a rare grouping of protein deposition diseases. Light-chain and transthyretin amyloidosis are the most common disease forms, often present with systemic involvement of vital organs including the heart, nerves, kidneys, and GI tracts of affected individuals. The Amyloidosis Program of Calgary examined 152 ATTR patients and 103 AL patients analyzing rates of vaccination, COVID-19 testing, infection outcomes, influence referrals, and excess deaths. Results showed 15 total PCR-confirmed COVID-19 infections in the tested population of amyloid patients, with a higher frequency of infections among patient with AL compared to the ATTR cohort (26.2% vs 5.1%). Four patients (26.6%) required hospital admission for COVID-19 infection, 2 ATTR, and 2 AL patients. Of the confirmed cases, 1 (0.07%) unvaccinated ATTR patient died of a COVID-19 infection. An excess of deaths was found in both the ATTR and AL cohorts when comparing pre-pandemic years 2018 and 2019 to the pandemic years of 2020 and 2021. The finding suggests that amyloidosis patients are likely at a high risk for severe COVID-19 infection and mortality, especially those of advanced age, those on an active treatment with chemotherapy, and those with concomitant B-cell or plasma cell disorder. The impact of virtual healthcare visits and pandemic measures on the excess of deaths observed requires further research.

Outcomes of renal transplantation in patients with AL amyloidosis: an international collaboration through The International Kidney and Monoclonal Gammopathy Research Group

Effective systemic therapies suppress toxic light chain production leading to an increased proportion of patients with light chain (AL) amyloidosis who survive longer albeit with end-stage renal disease. There is a critical need to identify patients in this population who benefit from renal transplantation. This multicenter, observational study from five countries includes 237 patients with AL amyloidosis who underwent renal transplantation between 1987 and 2020. With a median follow-up of 8.5 years, the median overall survival from renal transplantation was 8.6 years and was significantly longer in patients with complete and very good partial hematologic responses (CR + VGPR) compared to less than VGPR (9 versus 6.8 years; HR: 1.5, P = 0.04 [95% CI: 1-2.1]) at renal transplantation. Median graft survival was 7.8 years and was better in the CR + VGPR group (8.3 vs 5.7 years, HR: 1.4, P = 0.05 [95% CI: 1-2]). The frequency and time to amyloid recurrence in the graft was also lower (16% vs 37%, p = 0.01) and longer (median time not achieved vs 10 years, p = 0.001) in the CR + VGPR group. Comparing CR vs. VGPR there was no difference in overall or graft survival. Although 69 patients (29%) experienced hematologic relapse, treatment effectively prevented graft loss in the majority (87%). Renal transplantation in selected AL amyloidosis patients is associated with extended overall and renal graft survival. Patients with hematologic CR or VGPR have the most favorable outcomes, and these patients should be considered for renal transplantation.

Gene expression data analysis using Hellinger correlation in weighted gene co-expression networks (WGCNA)

Weighted gene co-expression network analysis (WGCNA) is used to detect clusters with highly correlated genes. Measurements of correlation most typically rely on linear relationships. However, a linear relationship does not always model pairwise functional-related dependence between genes. In this paper, we first compared 6 different correlation methods in their ability to capture complex dependence between genes in three different tissues. Next, we compared their gene-pairwise coefficient results and corresponding WGCNA results. Finally, we applied a recently proposed correlation method, Hellinger correlation, as a more sensitive correlation measurement in WGCNA. To test this method, we constructed gene networks containing co-expression gene modules from RNA-seq data of human frontal cortex from Alzheimer's disease patients. To test the generality, we also used a microarray data set from human frontal cortex, single cell RNA-seq data from human prefrontal cortex, RNA-seq data from human temporal cortex, and GTEx data from heart. The Hellinger correlation method captures essentially similar results as other linear correlations in WGCNA, but provides additional new functional relationships as exemplified by uncovering a link between inflammation and mitochondria function. We validated the network constructed with the microarray and single cell sequencing data sets and a RNA-seq dataset of temporal cortex. We observed that this new correlation method enables the detection of non-linear biologically meaningful relationships among genes robustly and provides a complementary new approach to WGCNA. Thus, the application of Hellinger correlation to WGCNA provides a more flexible correlation approach to modelling networks in gene expression analysis that uncovers novel network relationships.

[Cardiac amyloidosis: State of art in 2022]

The 3 main types of cardiac amyloidosis are linked to two protein precursors: AL amyloidosis secondary to free light chain deposits in the context of monoclonal gammopathy (mainly of undetermined significance or myeloma) and transthyretin amyloidosis (ATTR), comprising wild-type transthyretin amyloidosis (ATTRwt for wild type) and hereditary transthyretin amyloidosis (ATTRv for variant). These diseases are underdiagnosed and highly prevalent in common cardiac phenotypes in recent studies (heart failure with preserved ejection fraction, severe aortic stenosis, hypertrophic cardiomyopathy). Myocardial amyloid infiltration affects all cardiac structures and clinically promotes predominantly heart failure, conductive disorders and cardioembolic events. The search for extracardiac signs makes it possible to arouse diagnostic suspicion. Electrocardiogram, echocardiography and cardiac MRI can suspect cardiac amyloidosis. The diagnostic confirmation follows a simple algorithm including a systematic search for monoclonal gammapathy and a disphosphonate scintigraphy. Histological proof is necessary in case of AL or ATTR amyloidosis with concomitant monoclonal gammopathy in order to initiate specific treatment. Due to the late disease onset in ATTRv, genetic testing must be routine in all cases of ATTR. These diseases are no longer perceived as incurable since recent therapeutic innovations. A better knowledge of the disease is more than ever necessary.

Cutaneous Ossifying Amyloidoma

ABSTRACT

Amyloidoma, otherwise known as tumoral amyloidosis, is a localized deposition of amyloid (AL-type or AA type) without systemic amyloidosis. It is the rarest form of tissue amyloid deposition, and up to 7% of amyloidomas develop systemic amyloidosis.Cutaneous AL-type amyloidoma is considered by many authors as an unusual variant of primary cutaneous marginal zone lymphoma. Although cutaneous amyloidoma can form calcifications, ossification is extremely unusual, with only 1 case previously published to date.We report the case of a 75-year-old woman with voluminous and strikingly ossifying AL-type amyloidoma in the left pretibial skin. Her medical history included excision of hepatic hydatidic cysts 25 years prior and diffuse large B-cell lymphoma of the left parotid gland 8 years prior treated with chemotherapy and radiotherapy with complete response. After the diagnosis of amyloidoma, an extension study with cervical, chest, abdominal, and pelvic TC was performed, with no additional lesions found. Serum and protein electrophoresis revealed elevations in kappa light chain and IgA immunoglobulin levels but did not reveal monoclonal bands. In situ hybridization for immunoglobulin light chains showed monotypic kappa expression in plasma cells infiltrating the amyloidoma.Extensive ossification in amyloidomas can make diagnosis difficult; therefore, we describe an interesting case of this histopathologically peculiar amyloidoma.

Kinetic Mechanism of Amyloid-β-(16-22) Peptide Fibrillation

The kinetic mechanism of amyloid fibril formation by a peptide fragment containing seven residues of the amyloid-β protein Aβ-(16-22) was investigated. We found that the N- and C-terminal unprotected Aβ-(16-22), containing no aggregation nuclei, showed rapid fibrillation within seconds to minutes in a neutral aqueous buffer solution. The fibrillation kinetics were well described by the nucleation-elongation model, suggesting that primary nucleation was the rate-limiting step. On the basis of both experimental and theoretical analyses, the aggregated nucleus was estimated to be composed of 6-7 peptide molecules, wherein the two β-sheets were associated with their hydrophobic surfaces. Thin fibers with widths of 10-20 nm were formed, which increased their length and thickness, attaining a width of >20 nm over several tens of minutes, probably owing to the lateral association of the fibers. Electrostatic and hydrophobic interactions play important roles in aggregation. These results provide a basis for understanding the fibrillation of short peptides.

The Clinical Characteristics and Prognosis of Chinese Patients with Light-Chain Amyloidosis: A Retrospective Multicenter Analysis

To retrospectively identify the critical characteristics and prognostic factors of light-chain amyloidosis. Patients and Methods: Data were collected and compared from 91 patients who were diagnosed with light-chain amyloidosis at four hospitals between January 2010 and November 2018. We analyzed the clinical characteristics and performed an overall survival (OS) analysis. Results: Patients (median age, 60 years) were diagnosed with organ involvement of the kidney (91.2%), heart (56%), liver (14.3%), soft tissue (18.7%), or gastrointestinal tract (15.4%), and 68.1% of patients had more than two organs involved. Patients were most treated with bortezomib-based regimens (56%), and only one patient had autologous stem cell transplantation (auto-ASCT). The median OS was 36.33 months and was influenced by the ECOG score, renal involvement, cardiac involvement, hepatic involvement, and persistence of positive immunofixation. Patients who received bortezomib-based treatment had a trend of favorable OS compared to those who received non-bortezomib-based treatments, but the difference was not statistically significant. Although the overall number of organs involved was not related to OS, the number of organs involved in the heart, liver and kidney was related. Multivariate analysis indicated that cardiac involvement and negative hematologic response with persistence of positive immunofixation were independent prognostic factors for OS. Conclusion: Cardiac involvement and the hematologic response to treatment were independent prognostic factors for OS in light-chain amyloidosis patients.

The Diabetic Cardiorenal Nexus

The end-stage of the clinical combination of heart failure and kidney disease has become known as cardiorenal syndrome. Adverse consequences related to diabetes, hyperlipidemia, obesity, hypertension and renal impairment on cardiovascular function, morbidity and mortality are well known. Guidelines for the treatment of these risk factors have led to the improved prognosis of patients with coronary artery disease and reduced ejection fraction. Heart failure hospital admissions and readmission often occur, however, in the presence of metabolic, renal dysfunction and relatively preserved systolic function. In this domain, few advances have been described. Diabetes, kidney and cardiac dysfunction act synergistically to magnify healthcare costs. Current therapy relies on improving hemodynamic factors destructive to both the heart and kidney. We consider that additional hemodynamic solutions may be limited without the use of animal models focusing on the cardiomyocyte, nephron and extracellular matrices. We review herein potential common pathophysiologic targets for treatment to prevent and ameliorate this syndrome.

Impact of Tafamidis and Optimal Background Treatment on Physical Performance in Patients With Transthyretin Amyloid Cardiomyopathy

BACKGROUND

In patients with transthyretin amyloid cardiomyopathy, tafamidis was shown to slow the decline in 6-minute walking distance as compared with placebo. We aimed to define the impact of tafamidis and optimal background treatment on functional capacity as determined by cardiopulmonary exercise testing (CPET).

METHODS

Seventy-eight consecutive patients were enrolled in the study. They underwent CPET at baseline, and outcome defined as death or heart failure hospitalization was obtained for a time period of up to 30 months. Fifty-four patients completed a follow-up CPET at 9±3 months (range, 4-16 months). Improvement in peak VO₂ at follow-up was defined as ∆peak VO₂≥1.0 mL/(kg·min), stable peak VO₂ was defined as 0≤∆peak VO₂<1.0 mL/(kg·min), and decline in peak VO₂ was defined by ∆peak VO₂<0 mL/(kg·min).

RESULTS

Baseline peak VO₂>14 mL/(kg·min) as well as minute ventilation/carbon dioxide production slope≤34 were associated with a lower risk of death or heart failure hospitalization (P=0.002, P=0.007, respectively). In 54 patients, who received tafamidis and underwent repeat CPET testing, an improvement in physical performance (P=0.002) was observed at follow-up. When comparing pre and post-treatment parameters, 29 patients (54%) showed an increase in percent predicted peak VO₂ (P<0.0001), an improvement of peak VO₂ (P<0.0001), and better physical performance at follow-up (P<0.0001). Patients with stable or improved peak VO₂ had less advanced heart disease at baseline (P=0.046).

CONCLUSIONS

Our findings demonstrate that baseline peak VO₂ and baseline minute ventilation/carbon dioxide production slope predict outcomes and an improvement in physical performance as measured by CPET was observed in patients receiving tafamidis, who had less advanced disease at baseline, emphasizing the importance of early diagnosis.

Re-Definition of the Epidemiology of Cardiac Amyloidosis

The epidemiology of cardiac amyloidosis (CA), traditionally considered a rare and incurable disease, has changed drastically over the last ten years, particularly due to the advances in diagnostic methods and therapeutic options in the field of transthyretin CA (ATTR-CA). On the one hand, the possibility of employing cardiac scintigraphy with bone tracers to diagnose ATTR-CA without a biopsy has unveiled the real prevalence of the disease; on the other, the emergence of effective treatments, such as tafamidis, has rendered an early and accurate diagnosis critical. Interestingly, the following subgroups of patients have been found to have a higher prevalence of CA: elderly subjects > 75 years, patients with cardiac hypertrophy hospitalized for heart failure with preserved ejection fraction, subjects operated on for bilateral carpal tunnel syndrome, patients with cardiac hypertrophy not explained by concomitant factors and individuals with aortic valve stenosis. Many studies investigating the prevalence of CA in these particular populations have contributed to rewriting the epidemiology of the disease, increasing the awareness of the medical community for a previously underappreciated condition. In this review, we summarized the latest evidence on the epidemiology of CA according to the different clinical settings typically associated with the disease.

Multi-eGO: An in silico lens to look into protein aggregation kinetics at atomic resolution

Protein aggregation into amyloid fibrils is the archetype of aberrant biomolecular self-assembly processes, with more than 50 associated diseases that are mostly uncurable. Understanding aggregation mechanisms is thus of fundamental importance and goes in parallel with the structural characterization of the transient oligomers formed during the process. Oligomers have been proven elusive to high-resolution structural techniques, while the large sizes and long time scales, typical of aggregation processes, have limited the use of computational methods to date. To surmount these limitations, we here present multi-eGO, an atomistic, hybrid structure-based model which, leveraging the knowledge of monomers conformational dynamics and of fibril structures, efficiently captures the essential structural and kinetics aspects of protein aggregation. Multi-eGO molecular dynamics simulations can describe the aggregation kinetics of thousands of monomers. The concentration dependence of the simulated kinetics, as well as the structural features of the resulting fibrils, are in qualitative agreement with in vitro experiments carried out on an amyloidogenic peptide from Transthyretin, a protein responsible for one of the most common cardiac amyloidoses. Multi-eGO simulations allow the formation of primary nuclei in a sea of transient lower-order oligomers to be observed over time and at atomic resolution, following their growth and the subsequent secondary nucleation events, until the maturation of multiple fibrils is achieved. Multi-eGO, combined with the many experimental techniques deployed to study protein aggregation, can provide the structural basis needed to advance the design of molecules targeting amyloidogenic diseases.

Supportive Care and Symptom Management for Patients With Immunoglobulin Light Chain (AL) Amyloidosis

Immunoglobulin light chain (AL) amyloidosis is a disorder of clonal plasma cells characterized by deposition of amyloid fibrils in a variety of tissues, leading to end-organ injury. Renal or cardiac involvement is most common, though any organ outside the central nervous system can develop amyloid deposition, and symptomatic presentations may consequently vary. The variability and subtlety of initial clinical presentations may contribute to delayed diagnoses, and organ involvement is often quite advanced and symptomatic by the time a diagnosis is established. Additionally, while organ function can improve with plasma-cell-directed therapy, such improvement lags behind hematologic response. Consequently, highly effective supportive care, including symptom management, is essential to improve quality of life and to maximize both tolerance of therapy and likelihood of survival. Considering the systemic nature of the disease, close collaboration between clinicians is essential for effective management.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Molecular Mechanism of Pathogenesis and Treatment Strategies for AL Amyloidosis

In amyloid light-chain (AL) amyloidosis, small B-cell clones (mostly plasma cell clones) present in the bone marrow proliferate and secrete unstable monoclonal free light chains (FLCs), which form amyloid fibrils that deposit in the interstitial tissue, resulting in organ injury and dysfunction. AL amyloidosis progresses much faster than other types of amyloidosis, with a slight delay in diagnosis leading to a marked exacerbation of cardiomyopathy. In some cases, the resulting heart failure is so severe that chemotherapy cannot be administered, and death sometimes occurs within a few months. To date, many clinical studies have focused on therapeutics, especially chemotherapy, to treat this disease. Because it is necessary to promptly lower FLC, the causative protein of amyloid, to achieve a hematological response, various anticancer agents targeting neoplastic plasma cells are used for the treatment of this disease. In addition, many basic studies using human specimens to elucidate the pathophysiology of AL have been conducted. Gene mutations associated with AL, the characteristics of amyloidogenic LC, and the structural specificity of amyloid fibrils have been clarified. Regarding the mechanism of cellular and tissue damage, the mass effect due to amyloid deposition, as well as the toxicity of pre-fibrillar LC, is gradually being elucidated. This review outlines the pathogenesis and treatment strategies for AL amyloidosis with respect to its molecular mechanisms.

New Evidence on a Distinction between Aβ40 and Aβ42 Amyloids: Thioflavin T Binding Modes, Clustering Tendency, Degradation Resistance, and Cross-Seeding

The relative abundance of two main Abeta-peptide types with different lengths, Aβ40 and Aβ42, determines the severity of the Alzheimer’s disease progression. However, the factors responsible for different behavior patterns of these peptides in the amyloidogenesis process remain unknown. In this comprehensive study, new evidence on Aβ40 and Aβ42 amyloid polymorphism was obtained using a wide range of experimental approaches, including custom-designed approaches. We have for the first time determined the number of modes of thioflavin T (ThT) binding to Aβ40 and Aβ42 fibrils and their binding parameters using a specially developed approach based on the use of equilibrium microdialysis, which makes it possible to distinguish between the concentration of the injected dye and the concentration of dye bound to fibrils. The binding sites of one of these modes located at the junction of adjacent fibrillar filaments were predicted by molecular modeling techniques. We assumed that the sites of the additional mode of ThT-Aβ42 amyloid binding observed experimentally (which are not found in the case of Aβ40 fibrils) are localized in amyloid clots, and the number of these sites could be used for estimation of the level of fiber clustering. We have shown the high tendency of Aβ42 fibers to form large clots compared to Aβ40 fibrils. It is probable that this largely determines the high resistance of Aβ42 amyloids to destabilizing effects (denaturants, ionic detergents, ultrasonication) and their explicit cytotoxic effect, which we have shown. Remarkably, cross-seeding of Aβ40 fibrillogenesis using the preformed Aβ42 fibrils changes the morphology and increases the stability and cytotoxicity of Aβ40 fibrils. The differences in the tendency to cluster and resistance to external factors of Aβ40 and Aβ42 fibrils revealed here may be related to the distinct role they play in the deposition of amyloids and, therefore, differences in pathogenicity in Alzheimer’s disease.

Transthyretin Amyloid Cardiomyopathy: Impact of Transthyretin Amyloid Deposition in Myocardium on Cardiac Morphology and Function

Background: Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) is increasingly being recognized as a cause of left ventricular (LV) hypertrophy (LVH) and progressive heart failure in elderly patients. However, little is known about the cardiac morphology of ATTR-CM and the association between the degree of TTR amyloid deposition and cardiac dysfunction in these patients. Methods: We studied 28 consecutive patients with ATTR-CM and analyzed the relationship between echocardiographic parameters and pathological features using endomyocardial biopsy samples. Results: The cardiac geometries of patients with ATTR-CM were mainly classified as concentric LVH (96.4%). The relative wall thickness, a marker of LVH, tended to be positively correlated with the degree of non-cardiomyocyte area. The extent of TTR deposition was positively correlated with enlargement of the non-cardiomyocyte area, and these were positively correlated with LV diastolic dysfunction. Additionally, the extent of the area containing TTR was positively correlated with the percentage of cardiomyocyte nuclei stained for 8-hydroxy-2′deoxyguanosine, a marker of reactive oxygen species (ROS). ROS accumulation in cardiomyocytes was positively correlated with LV systolic dysfunction. Conclusion: Patients with ATTR-CM mainly displayed concentric LVH geometry. TTR amyloid deposition was associated with cardiac dysfunction via increased non-cardiomyocyte area and ROS accumulation in cardiomyocytes.

Amyloid Formation in Nanoliter Droplets

Processes that monitor the nucleation of amyloids and characterize the formation of amyloid fibrils are vital to medicine and pharmacology. In this study, we observe the nucleation and formation of lysozyme amyloid fibrils using a facile microfluidic system to generate nanoliter droplets that can control the flow rate and movement of monomer-in-oil emulsion droplets in a T-junction microchannel. Using a fluorescence assay, we monitor the nucleation and growth process of amyloids based on the volume of droplets. Using the microfluidic system, we demonstrate that the lag phase, which is vital to amyloid nucleation and growth, is reduced at a lower droplet volume. Furthermore, we report a peculiar phenomenon of high amyloid formation at the edge of a bullet-shaped droplet, which is likely due to the high local monomer concentration. Moreover, we discovered that amyloid fibrils synthesized in the nanoliter droplets are shorter and thicker than fibrils synthesized from a bulk solution via the conventional heating method. Herein, a facile procedure to observe and characterize the nucleation and growth of amyloid fibrils using nanoliter droplets is presented, which is beneficial for investigating new features of amyloid fibril formation as an unconventional synthetic method for amyloid fibrils.

Anisotropic Microgels Show Their Soft Side

Anisotropic, submicrometer-sized particles are versatile systems providing interesting features in creating ordering in two-dimensional systems. Combining hard ellipsoids with a soft shell further enhances the opportunities to trigger and control order and alignment. In this work, we report rich 2D phase behavior and show how softness affects the ordering of anisotropic particles at fluid oil-water interfaces. Three different core-shell systems were synthesized such that they have the same elliptical hematite-silica core but differ with respect to thickness and stiffness of the soft microgel shell. Compression isotherms, the shape of individual core-shell microgels, and their 2D order at a decane-water interface are investigated by means of the Langmuir-Blodgett technique combined with ex-situ atomic force microscopy (AFM) imaging as well as dissipative particle dynamics (DPD) simulations. We show how the softness, size, and anisotropy of the microgel shell affect the side-to-side vs tip-to-tip ordering of anisotropic hybrid microgels as well as the alignment with respect to the direction of compression in the Langmuir trough. A large, soft microgel shell leads to an ordered structure with tip-to-tip alignment directed perpendicular to the direction of compression. In contrast, a thin and harder microgel shell leads to side-to-side ordering orientated parallel to the compression direction. In addition, the thin and harder microgel shell induces clustering of the microgels in the dilute state, indicating the presence of strong capillary interactions. Our findings highlight the relevance of softness for the complex ordering of anisotropic hybrid microgels at interfaces.

A Rare Cause of Liver Cirrhosis and Gastritis: Primary Gastrointestinal Amyloidosis in a Patient With Multiple Myeloma

A 65-year-old male with a 25-year history of chronic alcoholism presented to the emergency department for a two-week history of non-radiating right upper quadrant abdominal pain associated with pruritus, nausea, coffee-ground emesis, and clay-colored stools. The exam was notable for icteric sclera, right upper quadrant abdominal tenderness, ascites, and hepatomegaly. Initial workup revealed new-onset unexplained elevated liver enzyme. The CT scan revealed diffuse liver cirrhosis, periportal lymphadenopathy, and stigmata of portal hypertension including hepatosplenomegaly, ascites, and varices. Esophagogastroduodenoscopy (EGD) with endoscopic ultrasound was performed, which showed gastritis and enlarged porta hepatis, which was ultimately biopsied and revealed extracellular amyloid deposition in peri-sinusoidal spaces consistent with amyloidosis. Transesophageal echocardiogram raised suspicion for cardiac involvement with amyloid deposit. The patient was started on steroids and chemotherapy with daratumumab, however his condition was complicated by septic shock, which led to an admission in the ICU followed by endotracheal intubation and multi-organ failure and eventual palliative care. Our case highlights the importance of clinical suspicion of GI amyloidosis in patients with constitutional symptoms including fatigue, weight loss, and unexplained liver disease. Once amyloidosis is considered, the diagnosis can be obtained by tissue biopsy from either the GI tract or subcutaneous adipose tissue.

[Gene therapy options for hereditary transthyretin-related amyloidosis]

Hereditary transthyretin-related amyloidosis (ATTRv) is a rare autosomal dominant disease and is fatal if left untreated. It is caused by mutations in the transthyretin gene. All known mutations induce misfolding of the tetrameric transthyretin molecule and protein deposits in multiple organs. In peripheral nerves this result in sensorimotor and autonomic polyneuropathy and in cardiac muscle it causes cardiomyopathy. Untreated ATTRv is characterized by an irreversible and progressive course and death 7-11 years after symptom onset. Treatment options consist of TTR stabilizing drugs, such as tafamidis and active agents that selectively interfere at the mRNA level, the so-called gene silencers patisiran and inotersen. All forms of treatment aim to prevent amyloid tissue deposition in tissues and organ dysfunction. Patisiran works by RNA interference on endogenous mechanisms of gene expression. It results in the cleavage of TTR-mRNA using the cytoplasmatic RNA-induced silencing complex. Inotersen, an antisense oligonucleotide, degrades TTR-mRNA via activation of nuclear RNase H. Both mechanisms result in a significant reduction of TTR protein serum levels. The efficacy could be demonstrated by slowing or improving neuropathy progression in the phase III study APOLLO (patisiran) or the NEURO-TTR study (inotersen). Furthermore, the use of both agents led to an improvement in the quality of life in patients with ATTRv. Both forms of treatment are approved in Germany since August 2018 for polyneuropathy stages 1 and 2 according to Coutinho. The choice of treatment should be carried out individually considering drug formulation, contraindications and the necessary safety monitoring controls.

Modified Body Mass Index as a Novel Nutritional and Prognostic Marker in Patients with Cardiac Amyloidosis

The nutritional assessment is gaining clinical relevance since cardiac cachexia and malnutrition are emerging as novel markers of functional status and prognosis in many cardiovascular disorders, including cardiac amyloidosis (CA). This study aimed to evaluate the prognostic role of different nutritional indices for cardiovascular mortality in patients with CA and subgroups. Fifty CA patients (26 AL and 24 ATTR wild-type) were retrospectively analyzed. All patients underwent a comprehensive clinical and laboratory evaluation. Conventional body mass index (cBMI), modified BMI (mBMI), new BMI (nBMI) and prognostic nutritional index (PNI) were analyzed. Multivariate regression analysis was performed to identify the association between nutritional and other clinical-laboratory parameters with cardiovascular death. Compared to ATTRwt patients, those with AL showed lower mBMI values. No significant difference was observed for the other nutritional indices. During a median follow-up of 11.2 months, a lower mBMI quartile was associated with worse survival, in both groups. In multivariate analysis, mBMI emerged as an independent predictor for cardiovascular death. This study showed that mBMI is a novel index of malnutrition and an independent risk factor for cardiovascular mortality in patients with CA in both AL and ATTRwt form.

Treatment of Transthyretin Amyloid Cardiomyopathy: The Current Options, the Future, and the Challenges

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressively debilitating, rare disease associated with high mortality. ATTR-CM occurs when TTR amyloid protein builds up in the myocardium along with different organs, most commonly the peripheral and the autonomic nervous systems. Managing the cardiac complications with standard heart failure medications is difficult due to the challenge to maintain a balance between the high filling pressure associated with restricted ventricular volume and the low cardiac output. To date, tafamidis is the only agent approved for ATTR-CM treatment. Besides, several agents, including green tea, tolcapone, and diflunisal, are used off-label in ATTR-CM patients. Novel therapies using RNA interference also offer clinical promise. Patisiran and inotersen are currently approved for ATTR-polyneuropathy of hereditary origin and are under investigation for ATTR-CM. Monoclonal antibodies in the early development phases carry hope for amyloid deposit clearance. Despite several drug candidates in the clinical development pipeline, the small ATTR-CM patient population raises several challenges. This review describes current and future therapies for ATTR-CM and sheds light on the clinical development hurdles facing them.

Pulmonary Manifestations of Primary Humoral Deficiencies

Primary immunodeficiencies are a group of conditions characterized by developmental or functional alterations in the immune system caused by hereditary genetic defects. Primary immunodeficiencies may affect either the innate or the adaptive (humoral and cellular) immune system. Pulmonary complications in primary humoral deficiencies are frequent and varied and are associated with high morbidity and mortality rates. The types of complications include bronchiectasis secondary to recurrent respiratory infections and interstitial pulmonary involvement, which can be associated with autoimmune cytopenias, lymphoproliferation, and a range of immunological manifestations. Early detection is key to timely management. Immunoglobulin replacement therapy reduces the severity of disease, the frequency of exacerbations, and hospital admissions in some primary humoral deficiencies. Therefore, the presence of pulmonary disease with concomitant infectious and/or autoimmune complications should raise suspicion of primary humoral deficiencies and warrants a request for immunoglobulin determination in blood. Once diagnosis is confirmed; early immunoglobulin replacement therapy will improve the course of the disease. Further studies are needed to better understand the pathogenesis of pulmonary disease related to primary humoral deficiencies and favor the development of targeted therapies that improve the prognosis of patients.

Future Developments in Light Chain Amyloidosis Management

Light chain (AL) amyloidosis is challenging to diagnose, and it should be considered a cardiac emergency. There have been a great deal of advances in the treatment of AL amyloidosis from initial descriptions of melphalan therapy until the recent approval of the first AL amyloidosis specific drug (daratumumab). Comprehension of the pathophysiology and biology of AL amyloidosis is crucial to understanding the major therapeutic targets in which light chain stability remains as a major key target of therapy. Organ dysfunction is a result not only from disruption of organ architecture but also direct cellular toxicity. Novel antiplasma cell agents for AL like isatuximab (anti CD-38 monoclonal antibody), belantamab (anti-BCMA monoclonal antibody), and elotuzumab (anti-SLAMF7 monoclonal antibody) are currently under investigation. Both diagnostic and therapeutic advances make the future of AL management bright while acknowledging the complexity of this patient population and focusing on a multidisciplinary approach.

Evaluation and Management Strategies for GI Involvement with Amyloidosis

Amyloidosis is a heterogeneous disease that can cause a wide array of nonspecific symptoms when the gastrointestinal (GI) tract is involved, including weight loss, early satiety, change in bowel habits with diarrhea, constipation, or alternating bowel pattern. Endoscopy with biopsy for Congo red staining establishes the diagnosis and fibril subtyping helps to guide targeted treatment options. Light chain amyloidosis is the most frequent subtype found throughout the GI tract. Transthyretin amyloidosis is most likely to be found on rectal biopsy. Management of the symptoms of GI tract involvement with amyloidosis relate to addressing the underlying symptom complex that is produced and generally abstracted from the management of severe forms of functional GI disorders. Attention to improving symptom management and nutrition status can improve quality of life in these patients.

18F-fluoride PET/MR in cardiac amyloid: A comparison study with aortic stenosis and age- and sex-matched controls

OBJECTIVES

Cardiac MR is widely used to diagnose cardiac amyloid, but cannot differentiate AL and ATTR subtypes: an important distinction given their differing treatments and prognoses. We used PET/MR imaging to quantify myocardial uptake of 18F-fluoride in ATTR and AL amyloid patients, as well as participants with aortic stenosis and age/sex-matched controls.

METHODS

In this prospective multicenter study, patients were recruited in Edinburgh and New York and underwent 18F-fluoride PET/MR imaging. Standardized volumes of interest were drawn in the septum and areas of late gadolinium enhancement to derive myocardial standardized uptake values (SUV) and tissue-to-background ratio (TBRMEAN) after correction for blood pool activity in the right atrium.

RESULTS

53 patients were scanned: 18 with cardiac amyloid (10 ATTR and 8 AL), 13 controls, and 22 with aortic stenosis. No differences in myocardial TBR values were observed between participants scanned in Edinburgh and New York. Mean myocardial TBRMEAN values in ATTR amyloid (1.13 ± 0.16) were higher than controls (0.84 ± 0.11, P = .0006), aortic stenosis (0.73 ± 0.12, P < .0001), and those with AL amyloid (0.96 ± 0.08, P = .01). TBRMEAN values within areas of late gadolinium enhancement provided discrimination between patients with ATTR (1.36 ± 0.23) and all other groups (e.g., AL [1.06 ± 0.07, P = .003]). A TBRMEAN threshold >1.14 in areas of LGE demonstrated 100% sensitivity (CI 72.25 to 100%) and 100% specificity (CI 67.56 to 100%) for ATTR compared to AL amyloid (AUC 1, P = .0004).

CONCLUSION

Quantitative 18F-fluoride PET/MR imaging can distinguish ATTR amyloid from other similar phenotypes and holds promise in improving the diagnosis of this condition.

Diagnostic Value of 11C-PIB PET/MR in Cardiac Amyloidosis

Background

The thioflavin T derivative, 11C-Pittsburgh-B (PIB), is used for Alzheimer's disease imaging because it specifically binds to β-amyloid protein deposits in the brain. The aim of this study was to estimate the diagnostic value of combined 11C-PIB positron emission tomography/magnetic resonance (PET/MR) in cardiac amyloidosis (CA).

Methods

We enrolled 23 heart failure patients with suspected CA based on echocardiographic and electrocardiograph findings. All patients underwent cardiac 11C-PIB PET/MR and non-cardiac biopsy within one week. We also enrolled eight healthy volunteers that underwent cardiac 11C-PIB PET/MR as a control group. The cardiac magnetic resonance (CMR) protocol included cine imaging, late gadolinium enhancement (LGE), and native and post-contrast T1 mapping. Extracellular volume (ECV) was measured using pre- and post-contrast T1 mapping images. LVEF, IVSD, LVPW, LVmass, LVESV, LVEDV, native T1 value, ECV, and maximum uptake of myocardial tissue-to-blood background ratio (TBR) values were obtained from PET/MR images in all patients and healthy subjects.

Results

Thirteen out of twenty-three heart failure patients were clinically diagnosed with CA. The remaining 10 patients were CA-negative (non-CA patient group). Twelve of the thirteen CA patients showed diffuse transmural LGE patterns, whereas LGE was either absent or patchy in the non-CA patients. The diagnostic sensitivity and specificity of TBRmax were 92.3 and 100%, respectively, at a cut-off value of 1.09. Several CMR imaging parameters (LVEF, IVSD, LVmass, LVEDV, LVESV, LVPW, native T1 value and ECV) and TBR showed significant differences between CA patients, non-CA patients, and healthy controls (P &lt; 0.05). Native T1 mapping values positively correlated with TBRmax values in CA and non-CA patients (r = 0.38, P = 0.0004).

Conclusions

11C-PIB PET/MRI is a valuable tool for the accurate and non-invasive diagnosis of CA because it distinguishes CA patients from non-CA patients and healthy subjects with high specificity and sensitivity. Moreover, native T1 mapping values positively correlated with TBRmax values in CA and non-CA patients. In the future, larger cohort studies are necessary to confirm our findings.

Clinical Clues and Diagnostic Workup of Cardiac Amyloidosis

Cardiac amyloidosis is increasingly recognized as an underlying cause of left ventricular wall thickening, heart failure, and arrhythmia with variable clinical presentation. Due to the subtle cardiac findings in early transthyretin cardiac amyloidosis and the availability of therapies that can modify but not reverse the disease progression, early recognition is vital. In light chain amyloidosis, timely diagnosis and treatment can significantly improve survival. In this manuscript, we review the clinical, imaging, and electrocardiographic clues that should raise suspicion for cardiac amyloidosis and provide a simplified diagnostic workup algorithm that ensures an accurate diagnosis. The evolution of the noninvasive diagnosis of cardiac amyloidosis has significantly influenced our understanding of disease prevalence, presentations, and outcomes. However, clinical recognition of clues and red flags remains the most important factor in advancing the care of patients with cardiac amyloidosis.

Light Chain Amyloidosis: Epidemiology, Staging, and Prognostication

Amyloidosis is a disorder of protein misfolding and metabolism in which insoluble fibrils are deposited in various tissues, causing organ dysfunction and eventually death. Out of the 60-plus heterogeneous amyloidogenic proteins that have been identified, approximately 30 are associated with human disease. The unifying feature of these proteins is their tendency to form beta-pleated sheets aligned in an antiparallel fashion. These sheets then form rigid, nonbranching fibrils that resist proteolysis, causing mechanical disruption and local oxidative stress in affected organs such as the heart, liver, kidneys, nervous system, and gastrointestinal tract. Here we review the epidemiology of light chain amyloidosis, the staging, and the concomitant prognostication that is critical in determining the appropriate treatment.

Amyloid Formation by Globular Proteins: The Need to Narrow the Gap Between in Vitro and in Vivo Mechanisms

The globular to fibrillar transition of proteins represents a key pathogenic event in the development of amyloid diseases. Although systemic amyloidoses share the common characteristic of amyloid deposition in the extracellular matrix, they are clinically heterogeneous as the affected organs may vary. The observation that precursors of amyloid fibrils derived from circulating globular plasma proteins led to huge efforts in trying to elucidate the structural events determining the protein metamorphosis from their globular to fibrillar state. Whereas the process of metamorphosis has inspired poets and writers from Ovid to Kafka, protein metamorphism is a more recent concept. It is an ideal metaphor in biochemistry for studying the protein folding paradigm and investigating determinants of folding dynamics. Although we have learned how to transform both normal and pathogenic globular proteins into fibrillar polymers in vitro, the events occurring in vivo, are far more complex and yet to be explained. A major gap still exists between in vivo and in vitro models of fibrillogenesis as the biological complexity of the disease in living organisms cannot be reproduced at the same extent in the test tube. Reviewing the major scientific attempts to monitor the amyloidogenic metamorphosis of globular proteins in systems of increasing complexity, from cell culture to human tissues, may help to bridge the gap between the experimental models and the actual pathological events in patients.