Renal Involvement in Hereditary Transthyretin Amyloidosis: An Italian Single-Centre Experience

Hereditary transthyretin amyloidosis (ATTRv)

Hereditary transthyretin (TTR) amyloidosis (ATTRv amyloidosis) is a devastating disease characterized by broad range of clinical manifestations, including predominantly neurological, predominantly cardiac, and mixed phenotypes. This wide phenotypic variability hindered timely disease diagnosis and risk stratification in the past, especially in individuals with absent or uncharted family history. However, recent advances in noninvasive testing have led to greater awareness and earlier diagnosis. Further, medications have been discovered which proved effective in controlling the disease and improving outcomes including stabilizing TTR, silencing TTR variants, and removing TTR amyloid from affected tissues. Importantly, CRISPR gene editing, a groundbreaking technology, offers the unique potential to cure ATTRv amyloidosis, transforming lives and opening new doors in medical science. This review provides an update on ATTRv amyloidosis mechanisms, diagnosis, and management emphasizing the importance of early diagnosis as the steadfast underpinning for the capitalization of the advances in medical treatment to the benefit of the patients.

Serum Biomarkers in Transthyretin Amyloidosis: An Overview of Neurofilaments, Cardiac, Renal, and Gastrointestinal Involvement

Hereditary transthyretin amyloidosis (ATTRv, v for variant) is a genetic disorder characterized by the deposition of misfolded transthyretin (TTR) protein in tissues, resulting in progressive dysfunction of multiple organs, including the nervous system, heart, kidneys, and gastrointestinal (GI) tract. Noninvasive serum biomarkers have become key tools for diagnosing and monitoring ATTRv. This review examines the role of available biomarkers for neurological, cardiac, renal, gastrointestinal, and multisystemic involvement in ATTRv. A thorough understanding of these biomarkers is essential for effective disease management and therapeutic monitoring.

Long-term treatment of hereditary transthyretin amyloidosis with patisiran: multicentre, real-world experience in Italy

BACKGROUND

Hereditary transthyretin (ATTRv, v for variant) amyloidosis with polyneuropathy is a rare disease caused by mutations in the transthyretin gene. In ATTRv amyloidosis, multisystem extracellular deposits of amyloid cause tissue and organ dysfunction. Patisiran is a small interfering RNA molecule drug that reduces circulating levels of mutant and wild-type TTR proteins. Prior to its regulatory approval, patisiran was available in Italy through a compassionate use programme (CUP). The aim of this study was to analyse the long-term outcomes of patients who entered into the CUP.

METHODS

This was a multicentre, observational, retrospective study of patients with ATTRv amyloidosis treated with patisiran. The analysis included change from baseline to 12, 24, 36 and 48 months in familial amyloid polyneuropathy (FAP) stage, polyneuropathy disability (PND) class, neuropathy impairment score (NIS), modified body mass index (mBMI), Compound Autonomic Dysfunction Test (CADT), Karnofsky Performance Status (KPS) scale and Norfolk Quality of Life-Diabetic Neuropathy (QoL-DN) questionnaire. Safety data were also analysed.

RESULTS

Forty patients from 11 Italian centres were enrolled: 23 in FAP 1 (6 in PND 1 and 17 in PND 2) and 17 in FAP 2 (8 in PND 3a and 9 in PND 3b) stage. In this population, the mean NIS at baseline was 71.4 (± 27.8); mBMI, 917.1 (± 207) kg/m2; KPS, 67.1 (± 14.0); Norfolk QoL-DN, 62.2 (± 25.2); and CADT, 13.2 (± 3.3). Statistical analysis showed few significant differences from baseline denoting disease stability. No new safety signals emerged.

CONCLUSIONS

Patisiran largely stabilised disease in patients with ATTRv amyloidosis.

Emerging multisystem biomarkers in hereditary transthyretin amyloidosis: a pilot study

Hereditary transthyretin (ATTRv) amyloidosis is a rare, adult-onset, progressive, multisystemic condition caused by TTR pathogenic variants. Reliable biomarkers are needed to allow early diagnosis and to monitor disease severity and progression. We measured serum concentrations of growth differentiation factor-15 (GDF-15) and uromodulin (Umod) in ATTRv patients to evaluate correlations with standard markers of disease severity (FAP stage and PND score). Blood samples were collected from 16 patients diagnosed with ATTRv amyloidosis and a verified TTR variant and from 26 healthy controls. ATTRv patients were stratified by clinical phenotype (neurologic vs. mixed), genotype (V30M vs. non-V30M), and disease severity. We found significantly higher levels of serum GDF-15 in ATTRv patients compared with controls. Mean serum Umod levels were significantly lower in patients with ATTRv than controls. A positive correlation was found between serum Umod and estimated glomerular filtration rate (eGFR), while an inverse correlation was found with cystatin C levels. Conversely, GDF-15 showed a negative correlation with eGFR, and a direct correlation with cystatin C levels. No correlation was demonstrated between GDF-15 or Umod levels and traditional cardiac biomarkers. The results identify alteration of serum levels of GDF-15 and Umod in ATTRv amyloidosis.

Hereditary Transthyretin Amyloidosis and the Impact of Classic and New Treatments on Kidney Function: A Review

Hereditary transthyretin amyloidosis (ATTRv) is a rare, progressive, and life-threatening disease caused by misfolded transthyretin (TTR) proteins that aggregate as abnormal amyloid fibrils and accumulate throughout the body. The kidney is one of the main organs affected in amyloid light chain (AL) amyloidosis and ATTRv amyloidosis. The most common clinical presentation is proteinuria, which consists mainly of albumin; this is the first step in the natural history of ATTRv nephropathy. Not all TTR mutations are equal in terms of ATTRv kidney involvement. Kidney involvement in ATTRv itself is difficult to define, given the numerous associated confounding factors. There are several treatments available to treat ATTRv, including orthotopic liver transplant (OLT), which is the classic treatment for ATTRv. However, we should be careful regarding the use of calcineurin inhibitors in the setting of OLT because these can be nephrotoxic. New treatments for amyloidosis may have an impact on kidney function, including drugs that target specific pathways involved in the disease. Tafamidis and diflunisal, which are TTR stabilizers, patisiran (RNA interference agent), and inotersen (antisense oligonucleotide inhibitor) have been shown to reduce TTR amyloid. Tafamidis and patisiran are medications that have reduced the progression of kidney disease in amyloidosis, but inotersen and diflunisal may damage kidney function.

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

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

Predictors of developing renal dysfunction following diagnosis of transthyretin cardiac amyloidosis

BACKGROUND

In patients with transthyretin cardiac amyloidosis (ATTR-CA), renal dysfunction is a poor prognostic indicator. Limited data are available on variables that portend worsening renal function (wRF) among ATTR-CA patients.

OBJECTIVES

This study assesses which characteristics place patients at higher risk for the development of wRF (defined as a drop of ≥10% in glomerular filtration rate [GFR]) within the first year following diagnosis of ATTR-CA.

METHODS

We included patients with ATTR-CA (n = 134) evaluated between 2/2016 and 12/2022 and followed for up to 1 year at our amyloid clinic. Patients were stratified into two groups: a group with maintained renal function (mRF) and a group with wRF and compared using appropriate testing. Significant variables in the univariate analysis were included in the multivariable logistic regression model to determine characteristics associated with wRF.

RESULTS

Within a follow-up period of 326 ± 118 days, the median GFR% change measured -6% [-18%, +8]. About 41.8% (n = 56) had wRF, while the remainder had mRF. In addition, in patients with no prior history of chronic kidney disease (CKD), 25.5% developed de novo CKD. On multivariable logistic regression, only New York Heart Association (NYHA) class ≥III (odds ratio [OR]: 3.9, 95% confidence interval [CI]: [1.6-9.3]), history of ischemic heart disease (IHD) (OR: 0.3, 95% CI: [0.1-0.7]), and not receiving SGLT-2i (OR: 0.1, 95% CI: [0.02-0.5]) were significant predictors of wRF.

CONCLUSION

Our study demonstrated that the development of de novo renal dysfunction or wRF is common following the diagnosis of ATTR-CA. Additionally, we identified worse NYHA class and no prior history of IHD as significant predictors associated with developing wRF, while receiving SGLT-2i therapy appeared to be protective in this population.

Biomarkers of axonal damage to favor early diagnosis in variant transthyretin amyloidosis (A-ATTRv)

Early identification of ATTRv amyloidosis disease onset is still often delayed due to the lack of validated biomarkers of this disease. Light chain neurofilament (NfL) have shown promising results in early diagnosis in this disease, but data is still needed, including with alternative measuring methods. Our aim was to study the levels of NfL measured by ELISA. Furthermore, interstitial matrix metalloproteinase type 1 (MMP-1) serum levels were measured as a potential new biomarker in ATTRv. Serum NfL and MMP-1 were measured using ELISA assays in 90 participants (29 ATTR-V30M patients, 31 asymptomatic V30M-TTR variant carriers and 30 healthy controls). Median NfL levels among ATTRv amyloidosis patients were significantly higher (116 pg/mL vs 0 pg/mL in both comparison groups). The AUC comparing ATTRv amyloidosis patients and asymptomatic carriers was 0.90 and the NfL concentration of 93.55 pg/mL yielded a sensitivity of 79% and a specificity of 87%. NfL levels had a significant positive correlation with NIS values among patients. We found a negative significant correlation between eGFR and NfL levels. Finally, MMP1 levels were not different between groups. Evidence of NfL use for early diagnosis of ATTR-PN amyloidosis is growing. ELISA seems a reliable and available technique for it quantification. Decreased GFR could influence NfL plasma levels.

Serum neurofilament light chain: a promising early diagnostic biomarker for hereditary transthyretin amyloidosis?

BACKGROUND AND PURPOSE

Hereditary transthyretin amyloidosis (ATTRv) is a life-threatening disease caused by mutations in the gene encoding transthyretin (TTR). The recent therapeutic advances have underlined the importance of easily accessible, objective biomarkers of both disease onset and progression. Preliminary evidence suggests a potential role in this respect for neurofilament light chain (NfL). In this study, the aim was to determine serum NfL (sNfL) levels in a late-onset ATTRv population and evaluate whether it might represent a reliable biomarker of disease onset (i.e., 'conversion' from the asymptomatic status to symptomatic disease in TTR mutation carriers).

METHODS

In all, 111 individuals harbouring a pathogenic TTR variant (61 symptomatic ATTRv patients and 50 presymptomatic carriers) were consecutively enrolled. Fifty healthy volunteers were included as the control group. Ella™ apparatus was used to assess sNfL levels.

RESULTS

Serum NfL levels were increased in ATTRv patients compared to both presymptomatic carriers and healthy controls, whilst not differing between carriers and healthy controls. An sNfL cut-off of 37.10 pg/mL could discriminate between asymptomatic and symptomatic individuals with high diagnostic accuracy (area under the curve 0.958; p < 0.001), sensitivity (81.4%) and specificity (100%).

CONCLUSIONS

Serum NfL seems to be a promising biomarker of peripheral nerve involvement in ATTRv amyloidosis and might become a reliable, objective measure to detect the transition from the presymptomatic stage to the onset of symptomatic disease. Further longitudinal studies are needed to confirm such a role and determine whether it could equally represent a biomarker of disease progression and response to therapy.

Optimal practices for the management of hereditary transthyretin amyloidosis: real-world experience from Japan, Brazil, and Portugal

Hereditary transthyretin (ATTRv) amyloidosis is a rare and autosomal dominant disorder associated with mutations in the transthyretin gene. Patients present with diverse symptoms related to sensory, motor, and autonomic neuropathy, as well as gastrointestinal, ocular, cardiac, renal and orthopedic symptoms, resulting from the deposition of transthyretin amyloid fibrils in multiple organs. The progressive nature of ATTRv amyloidosis necessitates pre- and post-onset monitoring of the disease. This review article is primarily based on a collation of discussions from a medical advisory board meeting in August 2021. In this article, we summarize the best practices in amyloidosis centers in three major endemic countries for ATTRv amyloidosis (Japan, Brazil, and Portugal), where most patients carry the Val30Met mutation in the transthyretin gene and the patients' genetic background was proven to be the same. The discussions highlighted the similarities and differences in the management of asymptomatic gene mutation carriers among the three countries in terms of the use of noninvasive tests and tissue biopsies and timing of starting the investigations. In addition, this article discusses a set of practical tests and examinations for monitoring disease progression applicable to neurologists working in diverse medical settings and generalizable in non-endemic countries and areas. This set of assessments consists of periodic (every 6 to 12 months) evaluations of patients' nutritional status and autonomic, renal, cardiac, ophthalmologic, and neurological functions. Physical examinations and patient-reported outcome assessments should be also scheduled every 6 to 12 months. Programs for monitoring gene mutation carriers and robust referral networks can aid in appropriate patient management in pre- to post-onset stages. For pre- and post-symptom onset testing for ATTRv amyloidosis, various noninvasive techniques are available; however, their applicability differs depending on the medical setting in each country and region, and the optimal option should be selected in view of the clinical settings, medical environment, and available healthcare resources in each region.

Current Evidence Supporting the Role of Immune Response in ATTRv Amyloidosis

Hereditary transthyretin (ATTRv) amyloidosis with polyneuropathy, also known as familial amyloid polyneuropathy (FAP), represents a progressive, heterogeneous, severe, and multisystemic disease caused by pathogenic variants in the TTR gene. This autosomal-dominant neurogenetic disorder has an adult onset with variable penetrance and an inconstant phenotype, even among subjects carrying the same mutation. Historically, ATTRv amyloidosis has been viewed as a non-inflammatory disease, mainly due to the absence of any mononuclear cell infiltration in ex vivo tissues; nevertheless, a role of inflammation in its pathogenesis has been recently highlighted. The immune response may be involved in the development and progression of the disease. Fibrillary TTR species bind to the receptor for advanced glycation end products (RAGE), probably activating the nuclear factor κB (NF-κB) pathway. Moreover, peripheral blood levels of several cytokines, including interferon (IFN)-gamma, IFN-alpha, IL-6, IL-7, and IL-33, are altered in the course of the disease. This review summarizes the current evidence supporting the role of the immune response in ATTRv amyloidosis, from the pathological mechanisms to the possible therapeutic implications.

Natural course and determinants of short-term kidney function decline in hereditary transthyretin amyloidosis: a French observational study

Data regarding renal involvement in patients with hereditary transthyretin (ATTRv) amyloidosis are scarce and the natural course of chronic kidney disease (CKD) in this population remains unclear. This observational study, including adult patients diagnosed with ATTRv amyloidosis at the French Reference Centre for Cardiac Amyloidosis, investigated renal function outcome and its determinants. Multivariable logistic regression models identified factors associated with CKD at baseline. Determinants of the change in estimated glomerular filtration rate (eGFR) over 24 months of follow-up were assessed with a multivariable linear mixed-effects model. In total, 232 patients (78 women [34%], mean age: 64 years) with ATTRv amyloidosis were classified on the basis of their TTR variants: ATTRV122I (37%), ATTRV30M (29%), and other variants (34%). Median baseline eGFR was 78 ml/min/1.73 m². Seventy-two patients (31%) had an eGFR below 60 ml/min/1.73m² and 27/137 patients (20%) had significant proteinuria (urine protein/creatinine ratio ≥30 mg/mmol). Renal biopsy, performed in four cases, found typical Congo red-positive and TTR-labelled amyloid deposits in all cases. Older age (OR 1.07, p < .001) and a prior history of hypertension (OR 2.09, p = .04) were associated with a higher prevalence of CKD at baseline, whereas higher left ventricular global longitudinal strain (LVGLS) (OR 0.83, p < .001) was associated with a lower prevalence. The estimated change in eGFR was -7.12 [-9.61, -4.63] and -8.21 [-10.81, -5.60] ml/min/1.73 m² after 12 and 24 months of follow-up, respectively. eGFR decline was independently associated with older age ((67-74], coefficient= -14.35 mL/min/1.73 m², p < .01, >74, coefficient = -22.93 mL/min/1.73 m², p < .001, versus <56), ATTRV122I (coefficient = -17.17 mL/min/1.73m², p < .01, versus ATTRV30M) and LVGLS (coefficient = 1.22, p < .01). These data suggest that CKD is a common finding in patients with ATTRv amyloidosis, and that eGFR decline is rapid during the first year of evaluation. Older age, lower LVGLS and ATTRV122I were associated with a worse renal outcome. Further studies are now needed to evaluate effects of new targeted therapies on long term renal function.

Amyloidoses in Onco-Nephrology Practice: A Multidisciplinary Case-Based Conference Report

Introduction and Objective

Amyloidoses are a heterogeneous group of disorders resulting from deposition of amyloid fibrils into extracellular tissues. While the kidneys are one of the most frequent sites of amyloid deposition, amyloid deposits can also affect a wide range of organ systems, including the heart, liver, gastrointestinal tract, and peripheral nerves. The prognosis of amyloidosis, especially with cardiac involvement, remains poor; however, a collaborative approach applying new tools for diagnosis and management may improve outcomes. In September 2021, the Canadian Onco-Nephrology Interest Group hosted a symposium to discuss diagnostic challenges and recent advances in the management of amyloidosis from the perspectives of the nephrologist, cardiologist, and onco-hematologist.

Methods and Sources of Information

Through structured presentations, the group discussed a series of cases highlighting the varied clinical presentations of amyloidoses affecting the kidney and heart. Expert opinions, clinical trial findings, and publication summaries were used to illustrate patient-related and treatment-related considerations in the diagnosis and management of amyloidoses.

Key findings

(1) Overview of the clinical presentation of amyloidoses and the role of specialists in performing timely and accurate diagnostic workup; (2) review of best practices for multidisciplinary management of amyloidosis, including prognostic variables and determinants of treatment response; and (3) update on new and emerging treatments in the management of light chain and amyloid transthyretin amyloidoses.

Limitations

This conference featured multidisciplinary discussion of cases, and learning points reflect the assessments by the involved experts/authors.

Implications

Identification and management of amyloidoses can be facilitated with a multidisciplinary approach and higher index of suspicion from cardiologists, nephrologists, and hemato-oncologists. Increased awareness of clinical presentations and diagnostic algorithms for amyloidosis subtyping will lead to more timely interventions and improved clinical outcomes.

Serum Inflammatory Profile in Hereditary Transthyretin Amyloidosis: Mechanisms and Possible Therapeutic Implications

Hereditary transthyretin (ATTRv) amyloidosis is a severe, progressive, and heterogeneous multisystemic condition due to mutations in the TTR gene. Although multiple aspects of its molecular pathophysiological mechanisms have been elucidated over the years, it is possible to hypothesize different pathogenetic pathways. Indeed, we extensively investigated the serum levels of several molecules involved in the immune response, in a cohort of ATTRv patients and healthy controls (HCs). Sixteen ATTRv patients and twenty-five HCs were included in the study. IFN-alpha levels were higher in ATTRv patients than in HCs, as well as IFN-gamma levels. By contrast, IL-7 levels were lower in ATTRv patients than in HCs. No significant difference between groups was found regarding IL-1Ra, IL-6, IL-2, IL-4, and IL-33 levels. Correlation analysis did not reveal any significant correlation between IFN-α, IFN-γ, IL-7, and demographic and clinical data. Larger and longitudinal studies using ultrasensitive methods to perform a full cytokine profiling are needed to better elucidate the role of inflammation in ATTRv pathogenesis and to test the reliability of these molecules as possible biomarkers in monitoring patients' progression.

Pupillometric findings in ATTRv patients and carriers: results from a single-centre experience

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv) is a treatable multisystemic disease with great phenotypic heterogeneity. Among extra-neurological features, pupillary abnormalities have been reported, either related to amyloid deposition in the eye or to a progressive autonomic neuropathy.

OBJECTIVE

To evaluate the role of automated pupillometry, a non-invasive and rapid test able to provide objective and reproducible data on pupil size and reactivity, as a marker of disease severity in late-onset ATTRv patients.

PATIENTS AND METHODS

We performed automated pupillometry on a cohort of ATTRv patients and pre-symptomatic TTR mutation carriers and compared results to healthy controls. An exhaustive clinical and instrumental evaluation was performed on all enrolled subjects.

RESULTS

A statistically significant difference in most pupillometry parameters was found in ATTRv patients as compared to both carriers and healthy controls. Moreover, in ATTRv patients, we found a significant correlation between many pupillometry findings and disease duration, as well as widely accepted clinical scales and investigations (NIS, Sudoscan from feet, and Norfolk QoL-DN questionnaire).

CONCLUSIONS

We suggest pupillometry may play a role as a reliable and non-invasive biomarker to evaluate ATTRv disease severity and monitor its progression.

Trajectories of Kidney Function in Patients with ATTRv Treated with Gene Silencers

Hereditary transthyretin amyloidosis (ATTRv; v for "variant") is the most common form of hereditary amyloidosis, with an autosomal dominant inheritance and a variable penetrance. This disease has a significant variability in clinical presentation and multiorgan involvement. While kidney involvement in early-onset ATTRv has been reported in one-third of patients, in late-onset ATTRv it has generally been considered rare. In the present study, we describe trajectories of kidney function over time before and after treatment with gene silencing therapies in a cohort of 17 ATTRv patients with different mutations, coming from Italy (nine subjects treated with inotersen and eight patients treated with patisiran). The analysis of estimated glomerular filtration rate (eGFR) slopes revealed that the average change in eGFR was 0.01 mL/min/1.73 m2 per month before initiation and -0.23 mL/min/1.73 m2 per month during follow-up for inotersen and -0.62 mL/min/1.73 m2 per month before initiation and -0.20 mL/min/1.73 m2 per month during follow-up for patisiran. In conclusion, we did not observe any significant difference either between the two groups of treatment or within-group before and after therapy, so gene-silencing therapies may be considered safe for renal function in ATTRv and are not associated with a worsening of eGFR slope.

Nerve Conduction Studies of Dorsal Sural Nerve: Normative Data and Its Potential Application in ATTRv Pre-Symptomatic Subjects

The objective of the study is to provide age-related normative values for dorsal sural nerve (DSN) and to analyse its application during follow-up of hereditary transthyretin amyloidosis (ATTRv) pre-symptomatic subjects. We consecutively recruited ATTRv pre-symptomatic carriers in which clinical examination, cardiological evaluation, and nerve conduction studies of the sural nerve and DSN were performed. To provide normative data of DSN, neurophysiologic parameters from healthy controls referred to our service were entered into linear regression analyses to check the relative influence of age and height. A correction grid was then derived. We collected 231 healthy subjects: the mean DSN sensory nerve action potential (SNAP) amplitude was 9.99 ± 5.48 μV; the mean conduction velocity was 49.01 ± 5.31 m/s. Significant correlations were found between age and height with DSN SNAP amplitude. Fifteen ATTRv pre-symptomatic carriers were examined. Sural nerve NCS were normal in 12/15 and revealed low/borderline values in three subjects. Considering our correction grid, we found an abnormal DNS amplitude in 9/15 subjects and low/borderline values in 2/15. In ATTRv, early detection of peripheral nerve damage is crucial to start a disease-modifying treatment. DSN may be easily and reliably included in the routine neurophysiological follow-up of ATTRv pre-symptomatic subjects.

Novel approaches to diagnosis and management of hereditary transthyretin amyloidosis

Hereditary transthyretin amyloidosis (ATTRv) is a severe, adult-onset autosomal dominant inherited systemic disease predominantly affecting the peripheral and autonomic nervous system, heart, kidney and the eyes. ATTRv is caused by mutations of the transthyretin (TTR) gene, leading to extracellular deposition of amyloid fibrils in multiple organs including the peripheral nervous system. Typically, the neuropathy associated with ATTRv is characterised by a rapidly progressive and disabling sensorimotor axonal neuropathy with early small-fibre involvement. Carpal tunnel syndrome and cardiac dysfunction frequently coexist as part of the ATTRv phenotype. Although awareness of ATTRv polyneuropathy among neurologists has increased, the rate of misdiagnosis remains high, resulting in significant diagnostic delays and accrued disability. A timely and definitive diagnosis is important, given the emergence of effective therapies which have revolutionised the management of transthyretin amyloidosis. TTR protein stabilisers diflunisal and tafamidis can delay the progression of the disease, if treated early in the course. Additionally, TTR gene silencing medications, patisiran and inotersen, have resulted in up to 80% reduction in TTR production, leading to stabilisation or slight improvement of peripheral neuropathy and cardiac dysfunction, as well as improvement in quality of life and functional outcomes. The considerable therapeutic advances have raised additional challenges, including optimisation of diagnostic techniques and management approaches in ATTRv neuropathy. This review highlights the key advances in the diagnostic techniques, current and emerging management strategies, and biomarker development for disease progression in ATTRv.

Kidney involvement in hereditary transthyretin amyloidosis: a cohort study of 103 patients

Background

Hereditary transthyretin amyloidosis (ATTRv) is a disabling and life-threatening disease that primarily affects the nervous system and heart. Its kidney involvement has not been systematically studied, particularly in non-V30M mutations, and is not well known to nephrologists.

Methods

We conducted a retrospective study describing the kidney phenotype of all prevalent patients with ATTR mutations, with neurological or cardiac involvement or presymptomatic carriers, followed up in two university hospitals from the South of France between June 2011 and June 2021.

Results

A total of 103 patients were included, among whom 79 were symptomatic and 24 were presymptomatic carriers. Patients carried 21 different ATTR mutations and 54% carried the V30M mutation. After a mean follow-up of 7.9 ± 25.7 years, 30.4% of the symptomatic patients had developed chronic kidney disease (CKD) and 20.3% had a urinary protein:creatinine ratio ≥0.5 g/g. None of the presymptomatic carriers had CKD or proteinuria. In a multivariate analysis, late onset of symptoms (after 60 years), the V122I mutation and proteinuria were significantly associated with CKD. The median CKD-free survival in symptomatic patients was estimated at 81.0 years (interquartile range 77.1–84.9). It did not differ between V30M and non-V30M patients, but was lower in patients with the V122I mutation. The average age of the onset of CKD was 69.3 ± 13.0 years. In one 38-year-old V30M female who presented a kidney-predominant phenotype, treatment with patisiran resulted in remission of the nephrotic syndrome.

Conclusion

CKD affects almost one-third of patients with symptomatic ATTRv. The role of ATTRv per se in the development of CKD in this population remains to be determined, but some patients may benefit from specific therapies.