Genotype-phenotype correlation and course of transthyretin familial amyloid polyneuropathies in France

Patisiran, an RNAi Therapeutic, for Hereditary Transthyretin Amyloidosis

BACKGROUND

Patisiran, an investigational RNA interference therapeutic agent, specifically inhibits hepatic synthesis of transthyretin.

METHODS

In this phase 3 trial, we randomly assigned patients with hereditary transthyretin amyloidosis with polyneuropathy, in a 2:1 ratio, to receive intravenous patisiran (0.3 mg per kilogram of body weight) or placebo once every 3 weeks. The primary end point was the change from baseline in the modified Neuropathy Impairment Score+7 (mNIS+7; range, 0 to 304, with higher scores indicating more impairment) at 18 months. Other assessments included the Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QOL-DN) questionnaire (range, -4 to 136, with higher scores indicating worse quality of life), 10-m walk test (with gait speed measured in meters per second), and modified body-mass index (modified BMI, defined as [weight in kilograms divided by square of height in meters]×albumin level in grams per liter; lower values indicated worse nutritional status).

RESULTS

A total of 225 patients underwent randomization (148 to the patisiran group and 77 to the placebo group). The mean (±SD) mNIS+7 at baseline was 80.9±41.5 in the patisiran group and 74.6±37.0 in the placebo group; the least-squares mean (±SE) change from baseline was -6.0±1.7 versus 28.0±2.6 (difference, -34.0 points; P<0.001) at 18 months. The mean (±SD) baseline Norfolk QOL-DN score was 59.6±28.2 in the patisiran group and 55.5±24.3 in the placebo group; the least-squares mean (±SE) change from baseline was -6.7±1.8 versus 14.4±2.7 (difference, -21.1 points; P<0.001) at 18 months. Patisiran also showed an effect on gait speed and modified BMI. At 18 months, the least-squares mean change from baseline in gait speed was 0.08±0.02 m per second with patisiran versus -0.24±0.04 m per second with placebo (difference, 0.31 m per second; P<0.001), and the least-squares mean change from baseline in the modified BMI was -3.7±9.6 versus -119.4±14.5 (difference, 115.7; P<0.001). Approximately 20% of the patients who received patisiran and 10% of those who received placebo had mild or moderate infusion-related reactions; the overall incidence and types of adverse events were similar in the two groups.

CONCLUSIONS

In this trial, patisiran improved multiple clinical manifestations of hereditary transthyretin amyloidosis. (Funded by Alnylam Pharmaceuticals; APOLLO ClinicalTrials.gov number, NCT01960348 .).

Transthyretin amyloid polyneuropathies mimicking a demyelinating polyneuropathy

OBJECTIVE

To clearly define transthyretin familial amyloid polyneuropathies (TTR-FAPs) fulfilling definite clinical and electrophysiologic European Federation of Neurological Societies/Peripheral Nerve Society criteria for chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

From a cohort of 194 patients with FAP, 13 of 84 patients (15%) of French ancestry had late-onset demyelinating TTR-FAP. We compared clinical presentation and electrophysiology to a cohort with CIDP and POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes) syndrome. We assessed nerve histology and the correlation between motor/sensory amplitudes/velocities. Predictors of demyelinating TTR-FAP were identified from clinical and electrophysiologic data.

RESULTS

Pain, dysautonomia, small fiber sensory loss above the wrists, upper limb weakness, and absence of ataxia were predictors of demyelinating TTR-FAP (p < 0.01). The most frequent demyelinating features were prolonged distal motor latency of the median nerve and reduced sensory conduction velocity of the median and ulnar nerves. Motor axonal loss was severe and frequent in the median, ulnar, and tibial nerves (p < 0.05) in demyelinating FAP. Ulnar nerve motor amplitude <5.4 mV and sural nerve amplitude <3.95 μV were distinguishing characteristics of demyelinating TTR-FAP. Nerve biopsy showed severe axonal loss and occasional segmental demyelination-remyelination.

CONCLUSION

Misleading features of TTR-FAP fulfilling criteria for CIDP are not uncommon in sporadic late-onset TTR-FAP, which highlights the limits of European Federation of Neurological Societies/Peripheral Nerve Society criteria. Specific clinical aspects and marked electrophysiologic axonal loss are red flag symptoms that should alert to this diagnosis and prompt TTR gene sequencing.

Genetic Analysis of Hereditary Transthyretin Ala97Ser Related Amyloidosis

Genetic testing is the most reliable test for hereditary transthyretin related amyloidosis and should be performed in most cases of transthyretin amyloidosis (ATTR). ATTR is a rare but fatal disease with heterogeneous phenotypes; therefore, the diagnosis is sometimes delayed. With increasing attention and broader recognition on early manifestations of ATTR as well as emerging treatments, appropriate diagnostic studies, including the transthyretin (TTR) genetic test, to confirm the types and variants of ATTR are therefore fundamental to improve the prognosis. Genetic analyses with polymerase chain reaction (PCR) methods confirm the presence of TTR point mutations much more quickly and safer than conventional methods such as southern blot. Herein, we demonstrate genetic confirmation of the ATTR Ala97Ser mutation, the most common endemic mutation in Taiwan. The protocol comprises four main steps: collecting whole blood specimen, DNA extraction, genetic analysis of all four TTR exons with PCR, and DNA sequencing.

Positive Effectiveness of Tafamidis in Delaying Disease Progression in Transthyretin Familial Amyloid Polyneuropathy up to 2 Years: An Analysis from the Transthyretin Amyloidosis Outcomes Survey (THAOS)

INTRODUCTION

The effectiveness of tafamidis for the treatment of transthyretin familial amyloid polyneuropathy (TTR-FAP) was evaluated using data from the Transthyretin Amyloidosis Outcomes Survey (THAOS) registry.

METHODS

Subjects receiving tafamidis (n = 252) were compared with untreated subjects in a non-randomized, matched cohort analysis. Subjects were matched with up to four untreated controls by genetic mutation, region of birth, and mean treatment propensity score.

RESULTS

The matched, treated sample consisted predominantly of subjects with the Val30Met genotype (92.5%), from Portugal, and with a mean age of 40.4 years. Over the course of the 2-year follow-up period, subjects treated with tafamidis showed significantly less deterioration on the Neuropathy Impairment Score for Lower Limbs (p < 0.001) and its subscales (p < 0.023) compared with untreated subjects. There was significantly less deterioration among tafamidis-treated subjects compared with untreated subjects on the Norfolk Quality of Life scale (p < 0.001). There were no significant differences observed in functional (assessed by Karnofsky Performance Status Scale score) or nutritional (assessed by modified body mass index) status between the treated and untreated groups. The primary model which examined survival from baseline using the matched cohort was not able to yield estimates of the hazard ratio, as there were no deaths in the tafamidis-treated subjects.

CONCLUSION

These findings support the results from clinical trials and strengthen evidence of the effectiveness of tafamidis beyond conventional clinical trials.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00628745 FUNDING: Pfizer.

A device to measure secretion of individual sweat glands for diagnosis of peripheral neuropathy

There is a need for quantitative, precise assessment of small fiber peripheral nerve function. We tested a customized camera device and protocol designed to quantify secretions of individual sweat glands (SGs). Testing was performed on 178 healthy controls and 20 neuropathy subjects. Sweating was stimulated on a 2.25 cm² skin area by iontophoresis of pilocarpine. The camera imaged sweat from 50 to 400 sweat ducts. We calculated secretion rate of individual SGs, total sweat volume, and number of secreting SGs at four body sites. Neuropathy subjects were tested at the two distal sites to demonstrate the device's capability to detect abnormal sudomotor function. Normal ranges were calculated for each body site. Neuropathy subjects had lower sweat rates per SG, lower total sweat, and lower SG density. The normal values decreased with advancing age, were lower in females, and differed between body sites. There was good agreement with repeat testing. The device provides reliable, precise quantitative measures of sweat secretion from single SGs for characterization of sudomotor nerve function in healthy control subjects and in subjects with known peripheral neuropathy. The test combines the capabilities of existing tests of sudomotor function while providing additional capabilities.

Diagnosis and management of transthyretin familial amyloid polyneuropathy in Japan: red-flag symptom clusters and treatment algorithm

Hereditary ATTR (ATTRm) amyloidosis (also called transthyretin-type familial amyloid polyneuropathy [ATTR-FAP]) is an autosomal-dominant, adult-onset, rare systemic disorder predominantly characterized by irreversible, progressive, and persistent peripheral nerve damage. TTR gene mutations (e.g. replacement of valine with methionine at position 30 [Val30Met (p.Val50Met)]) lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, which form amyloid fibrils that deposit in peripheral nerves and various organs, giving rise to peripheral and autonomic neuropathy and several non-disease specific symptoms.

Phenotypic and genetic variability and non–disease-specific symptoms often delay diagnosis and lead to misdiagnosis. Red-flag symptom clusters simplify diagnosis globally. However, in Japan, types of TTR variants, age of onset, penetrance, and clinical symptoms of Val30Met are more varied than in other countries. Hence, development of a Japan-specific red-flag symptom cluster is warranted. Presence of progressive peripheral sensory-motor polyneuropathy and ≥1 red-flag sign/symptom (e.g. family history, autonomic dysfunction, cardiac involvement, carpal tunnel syndrome, gastrointestinal disturbances, unexplained weight loss, and immunotherapy resistance) suggests ATTR-FAP. Outside of Japan, pharmacotherapeutic options are first-line therapy. However, because of positive outcomes (better life expectancy and higher survival rates) with living donor transplant in Japan, liver transplantation remains first-line treatment, necessitating a Japan-specific treatment algorithm.

Herein, we present a consolidated review of the ATTR-FAP Val30Met landscape in Japan and summarize findings from a medical advisory board meeting held in Tokyo on 18th August 2016, at which a Japan-specific ATTR-FAP red-flag symptom cluster and treatment algorithm was developed. Beside liver transplantation, a TTR-stabilizing agent (e.g. tafamidis) is a treatment option. Early diagnosis and timely treatment using the Japan-specific red-flag symptom cluster and treatment algorithm might help guide clinicians regarding apt and judicious use of available treatment modalities.

Tafamidis delays neurological progression comparably across Val30Met and non-Val30Met genotypes in transthyretin familial amyloid polyneuropathy

Background and purpose

To better characterize the effects of tafamidis in non‐Val30Met patients with transthyretin familial amyloid polyneuropathy, this post hoc analysis compared the neurological results from a 12‐month, open‐label study of non‐Val30Met versus Val30Met patients at month 12 from the 18‐month, double‐blind, placebo‐controlled registration study. A baseline covariate adjusted analysis was used to control for differences in baseline neurological severity.

Methods

Neurological function was assessed using the Neuropathy Impairment Score – Lower Limbs (NIS‐LL) in three cohorts: Val30Met tafamidis (n = 64), Val30Met placebo (n = 61) and non‐Val30Met tafamidis (n = 21). The change in NIS‐LL from baseline to month 12 for Val30Met and non‐Val30Met tafamidis‐treated patients was compared with the change from baseline at month 12 for Val30Met placebo‐treated patients using a mixed‐effects model for repeated measures (MMRM).

Results

The baseline adjusted mean (standard error) change in NIS‐LL values at month 12 was similar for Val30Met [1.60 (0.78)] and non‐Val30Met [1.62 (1.43)] tafamidis‐treated patients and less than that observed in the Val30Met placebo‐treated group [4.72 (0.77); P = 0.0055 for Val30Met and P = 0.0592 for non‐Val30Met]. Based on the MMRM, the magnitude of change in both tafamidis‐treated cohorts was similar across the range of observed baseline NIS‐LL values, and was consistently less than that observed in the Val30Met placebo‐treated group at month 12.

Conclusions

This baseline‐adjusted analysis demonstrated that tafamidis treatment delayed neurological progression comparably in Val30Met and non‐Val30Met patients across a range of baseline NIS‐LL values. Neurological progression in these two genotype groups may be more similar than previously considered.

Transthyretin familial amyloid polyneuropathy: an update

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a progressive, fatal, inherited disorder first identified in Portugal and now recognized in all continents. Over the past decade, thanks to the availability of the genetic test, our knowledge on the range of clinical expressions of this disorder has expanded, including different patterns and progression rates of the neuropathy, as well as aspects of the cardiomyopathy, which can be prominent. In the mean time, new tools are being developed to detect earlier TTR amyloid deposition such as cardiac scintigraphy with technetium-labelled pyrophosphate tracers or small nerve fiber alterations from skin biopsies, or using neurophysiological approaches as well as magnetic resonance neurography (MRN). Such refinements, along with an increased awareness of the disease, should reduce the diagnostic delay and facilitate early treatment. In this regard, thanks to a better understanding of the TTR amyloid formation, major advances have been made, allowing for therapeutic developments which are less invasive than liver transplantation (LT). TTR stabilizer drugs are safe and seem to delay the disease progression in some groups of patients. Indeed, positive results have just been released from 2 phase III trials on TTR gene modifiers, namely silencing RNA and antisense oligonucleotide therapies. These recent advances open a new area in the field with the hope that we can safely bring about long-term stabilization of the disease. Furthermore, immunotherapies targeting the amyloid deposits are being explored.

Trial design and rationale for APOLLO, a Phase 3, placebo-controlled study of patisiran in patients with hereditary ATTR amyloidosis with polyneuropathy

BACKGROUND

Patisiran is an investigational RNA interference (RNAi) therapeutic in development for the treatment of hereditary ATTR (hATTR) amyloidosis, a progressive disease associated with significant disability, morbidity, and mortality.

METHODS

Here we describe the rationale and design of the Phase 3 APOLLO study, a randomized, double-blind, placebo-controlled, global study to evaluate the efficacy and safety of patisiran in patients with hATTR amyloidosis with polyneuropathy. Eligible patients are 18-85 years old with hATTR amyloidosis, investigator-estimated survival of ≥2 years, Neuropathy Impairment Score (NIS) of 5-130, and polyneuropathy disability score ≤IIIb. Patients are randomized 2:1 to receive either intravenous patisiran 0.3 mg/kg or placebo once every 3 weeks. The primary objective is to determine the efficacy of patisiran at 18 months based on the difference in the change in modified NIS+7 (a composite measure of motor strength, sensation, reflexes, nerve conduction, and autonomic function) between the patisiran and placebo groups. Secondary objectives are to evaluate the effect of patisiran on Norfolk-Diabetic Neuropathy quality of life questionnaire score, nutritional status (as evaluated by modified body mass index), motor function (as measured by NIS-weakness and timed 10-m walk test), and autonomic symptoms (as measured by the Composite Autonomic Symptom Score-31 questionnaire). Exploratory objectives include assessment of cardiac function and pathologic evaluation to assess nerve fiber innervation and amyloid burden. Safety of patisiran will be assessed throughout the study.

DISCUSSION

APOLLO represents the largest randomized, Phase 3 study to date in patients with hATTR amyloidosis, with endpoints that capture the multisystemic nature of this disease.

TRIAL REGISTRATION

This trial is registered at clinicaltrials.gov ( NCT01960348 ); October 9, 2013.

Long-term safety and efficacy of tafamidis for the treatment of hereditary transthyretin amyloid polyneuropathy: results up to 6 years

BACKGROUND

The objective of the present study was to evaluate the long-term safety and efficacy of tafamidis in treating hereditary transthyretin amyloid polyneuropathy.

METHODS

A prospectively planned interim analysis was conducted on an on-going, phase III, open-label extension study following an 18-month, randomized, controlled study and 12-month, open-label extension study in ATTRV30M patients and a single-arm, open-label study in non-ATTRV30M patients. Thirty-seven ATTRV30M patients received placebo for 18 months, then switched to tafamidis and 38 ATTRV30M patients and 18 non-ATTRV30M patients continuously received tafamidis from day 1, up to 6 years.

RESULTS

Long-term tafamidis was associated with a favourable safety/tolerability profile, without any unexpected adverse events. Patients initiating tafamidis at the start of the randomized study had less polyneuropathy progression versus those switching to tafamidis following 18 months of placebo and were less likely to progress to the next ambulatory stage after up to 6 years follow-up. In the patients who switched from placebo to tafamidis, polyneuropathy progression and deterioration in quality of life slowed significantly during long-term tafamidis treatment as compared with the previous placebo treatment. In non-ATTRV30M patients, some polyneuropathy progression was observed across all efficacy measures.

CONCLUSIONS

These data provide evidence for the long-term (up to 6 years) safety and efficacy of tafamidis.ClinicalTrials.gov: NCT00925002.

Design and Rationale of the Phase 3 ATTR-ACT Clinical Trial (Tafamidis in Transthyretin Cardiomyopathy Clinical Trial)

Transthyretin amyloidosis is a rare, life-threatening disease resulting from aggregation and deposition of transthyretin amyloid fibrils in various tissues. There are 2 predominate phenotypic presentations of the disease: transthyretin familial amyloid polyneuropathy, which primarily affects the peripheral nerves, and transthyretin cardiomyopathy (TTR-CM), which primarily affects the heart. However, there is a wide overlap with symptoms at presentation and disease course being highly variable and influenced by the underlying transthyretin mutation, age of the affected individual, sex, and geographic location. Treatment of transthyretin amyloidosis is typically focused on symptom management. Although tafamidis has been shown to delay neurologic progression of transthyretin familial amyloid polyneuropathy, there are no approved pharmacologic therapies shown to improve survival in TTR-CM. The natural history of TTR-CM is poorly characterized, which presents difficulties for the design of large-scale trials for new treatments. This review provides a brief overview of TTR-CM and the challenges of identifying clinically meaningful end points and study parameters to determine the efficacy of treatments for rare diseases. The design and rationale behind the ongoing phase 3 ATTR-ACT study (Tafamidis in Transthyretin Cardiomyopathy Clinical Trial), an international, multicenter, double-blind, placebo-controlled, randomized clinical trial, is also outlined. The ATTR-ACT study will provide important insight into the efficacy and safety of tafamidis for the treatment of TTR-CM.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01994889.

Autonomic Neuropathy and Albuminocytologic Dissociation in Cerebrospinal Fluid As the Presenting Features of Primary Amyloidosis: A Case Report

OBJECTIVE

Primary amyloidosis is a disease with a poor prognosis and multi-organ involvement. Here, we report the clinical and pathological features of a patient with primary amyloidosis featuring autonomic neuropathy as the initial symptom and albuminocytologic dissociation in the cerebrospinal fluid (CSF).

METHODS

The patient was a 60-year-old Chinese male with numbness, orthostatic hypotension, and gastrointestinal symptoms. For diagnosis, we performed an electromyogram (EMG), lumbar puncture, Bence Jones protein urine test, serum electrophoresis blood test, sural nerve and rectal membrane biopsies, transthyretin (TTR) gene sequencing, and bone marrow puncture.

RESULTS

Congo red staining of sural nerve and rectal membrane biopsies showed amyloid deposition and apple-green birefringence was visualized under polarized light microscopy. TTR gene sequencing showed no causative mutation. Following lumbar puncture, normal CSF cell counts and elevated CSF protein concentration (1,680 mg/L) were detected. Bone marrow puncture showed that out of the total number of whole blood cells, 0.56% were abnormal plasma cells and that 87.4% of the total number of plasma cells were abnormal. EMG results showed mixed peripheral nerve damage predominately in the sensory nerve fibers.

CONCLUSION

Obvious symptoms of neuropathy, particularly autonomic neuropathy, albuminocytologic dissociation, and organ function damage suggested a diagnosis of amyloidosis. In such patients, neurologists should use caution to differentiate between chronic inflammatory demyelinating polyneuropathy, primary amyloidosis, and familial amyloid neuropathy.

Management of asymptomatic gene carriers of transthyretin familial amyloid polyneuropathy

Transthyretin familial amyloid polyneuropathy (TTR‐FAP) is a rare, severe, and irreversible, adult‐onset, hereditary disorder caused by autosomal‐dominant mutations in the TTR gene that increase the intrinsic propensity of transthyretin protein to misfold and deposit systemically as insoluble amyloid fibrils in nerve tissues, the heart, and other organs. TTR‐FAP is characterized by relentless, progressively debilitating polyneuropathy, and leads to death, on average, within 10 years of symptom onset without treatment. With increased availability of disease‐modifying treatment options for a wider spectrum of patients with TTR‐FAP, timely detection of the disease may offer substantial clinical benefits. This review discusses mutation‐specific predictive genetic testing in first‐degree relatives of index patients diagnosed with TTR‐FAP and the structured clinical follow‐up of asymptomatic gene carriers for prompt diagnosis and early therapeutic intervention before accumulation of substantial damage. Muscle Nerve54: 353–360, 2016

Novel screening for transthyretin amyloidosis by using fat ultrasonography

We aimed to assess the possibility of using a noninvasive screening method for hereditary transthyretin amyloidosis by means of abdominal fat ultrasonography. Quantitative analysis of ultrasound B-mode images demonstrated a significant increase in mean echogenicity and a loss of the normal structure of the layers of fat tissue in patients with hereditary transthyretin amyloidosis (n = 19). The ultrasound features of the fat tissue and the degree of amyloid deposition seen histopathologically showed a significant correlation. These results suggest that abdominal fat ultrasonography may be a valuable method for screening for hereditary transthyretin amyloidosis. Ann Neurol 2017;81:604-608.

Tafamidis delays disease progression in patients with early stage transthyretin familial amyloid polyneuropathy: additional supportive analyses from the pivotal trial

BACKGROUND

Tafamidis, a non-NSAID highly specific transthyretin stabilizer, delayed neurologic disease progression as measured by Neuropathy Impairment Score-Lower Limbs (NIS-LL) in an 18-month, double-blind, placebo-controlled randomized trial in 128 patients with early-stage transthyretin V30M familial amyloid polyneuropathy (ATTRV30M-FAP). The current post hoc analyses aimed to further evaluate the effects of tafamidis in delaying ATTRV30M-FAP progression in this trial.

METHODS

Pre-specified, repeated-measures analysis of change from baseline in NIS-LL in this trial (ClinicalTrials.gov NCT00409175) was repeated with addition of baseline as covariate and multiple imputation analysis for missing data by treatment group. Change in NIS-LL plus three small-fiber nerve tests (NIS-LL + Σ3) and NIS-LL plus seven nerve tests (NIS-LL + Σ7) were assessed without baseline as covariate. Treatment outcomes over the NIS-LL, Σ3, Σ7, modified body mass index and Norfolk Quality of Life-Diabetic Neuropathy Total Quality of Life Score were also examined using multivariate analysis techniques.

RESULTS

Neuropathy progression based on NIS-LL change from baseline to Month 18 remained significantly reduced for tafamidis versus placebo in the baseline-adjusted and multiple imputation analyses. NIS-LL + Σ3 and NIS-LL + Σ7 captured significant treatment group differences. Multivariate analyses provided strong statistical evidence for a superior tafamidis treatment effect.

CONCLUSIONS

These supportive analyses confirm that tafamidis delays neurologic progression in early-stage ATTRV30M-FAP.

TRIAL REGISTRATION NUMBER

NCT00409175.

Familial amyloid polyneuropathy in Portugal: New genes modulating age-at-onset

Objectives

Familial amyloid polyneuropathy (FAP ATTRV30M) shows a wide variation in age‐at‐onset (AO) between clusters, families, and among generations. We will now explore some candidate genes involved in altered disease pathways in order to assess their role as genetic modifiers of AO, using a family‐centered approach.

Methods

We analyzed 62 tagging SNPs from nine genes‐NGAL,MMP‐9,BGN,MEK1,MEK2,ERK1,ERK2,HSP27, and YWHAZ – in a sample of 318 V30M Portuguese patients (106 families), currently under follow‐up. A generalized estimating equation analysis was used to take into account nonindependency of AO between relatives. Also, an in silico analysis was performed in order to assess the functional impact of significant variants associated with AO.

Results

We found for the first time variants from six genes (NGAL,BGN (in the female group), MEK1,MEK2,HSP27, and YWHAZ) that were significantly associated with early‐ and/or late‐onset. Then, we confirmed a strong synergistic interaction between NGAL and MMP‐9 genes. Additionally, by an in silico analysis, we found some variants for MEK1 gene that may alter binding of the transcription factors and that influence the regulation of gene expression regarding microRNA binding sites and splicing regulatory factors.

Interpretation

These findings showed that different genetic factors can modulate differently the onset of disease's symptoms and revealed new mechanisms with clinical implications in the genetic counseling and follow‐up of mutation carriers and could contribute for development of potential therapeutical targets.

Hereditary neuropathies: An update

Hereditary neuropathies are the most common inherited neuromuscular diseases. Charcot-Marie-Tooth (CMT) disease represents the most common form with an average prevalence ranging from 1/2500 to 1/1200, depending on the studies. To date and with the advances of the latest generation sequencing, more than 80 genes have been identified. Although the common clinical phenotype comprises a progressive distal muscle weakness and sensory loss, foot deformities and decreased or absent tendon reflexes, clinical and electrophysiological phenotypes exhibit great variability. Moreover, atypical phenotypes are arising, overlapping with spastic paraplegia, hereditary sensory neuropathies or amyotrophic lateral sclerosis. The causative genes are involved in various biological processes such as myelin development and maintenance, biosynthesis and degradation of proteins, neuronal structural maintenance, axonal transport, endocytosis, membrane dynamics, ion-channel function and the mitochondrial network. An accurate genetic diagnosis is important for appropriate genetic counselling and treatment options. Therapeutic advances, particularly small interfering RNA therapy, are encouraging in hereditary transthyretin amyloid neuropathy.

Sixty years of transthyretin familial amyloid polyneuropathy (TTR-FAP) in Europe: where are we now? A European network approach to defining the epidemiology and management patterns for TTR-FAP

Purpose of review

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a highly disabling, life-threatening disease characterized by progressive sensorimotor and autonomic neuropathy. The profile of the disease across Europe is inadequately understood at present.

Recent findings

The incidence and clinical presentation of TTR-FAP varies widely within Europe, with early and late-onset disease subtypes. In those regions in which the disease is endemic (Portugal, Sweden, Cyprus, and Majorca), a Val30Met substitution in the TTR gene is the predominant genetic cause, whereas in the rest of Europe, cases of TTR-FAP are mainly sporadic with genetic heterogeneity. Current management strategies lack cohesion and patients can experience years of misdiagnosis and suboptimal treatment.

Summary

The article aims to disseminate the findings and recommendations from two recent meetings of the European Network for TTR-FAP (ATTReuNET), a panel comprising representatives from 10 European countries (Bulgaria, Cyprus, France, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, and Turkey) with expertise in the diagnosis and management of TTR-FAP. We explore the epidemiology and genetic mark of TTR-FAP across Europe and assess current management strategies, with a view to developing an alternative framework – a networked approach to disease management with an emphasis on collaboration and sharing of best practice.

Hereditary and inflammatory neuropathies: a review of reported associations, mimics and misdiagnoses

Distinguishing between hereditary and inflammatory neuropathy is usually straightforward on clinical grounds with the help of a family history. There are nevertheless cases where the distinction is less clear. The advent of molecular genetics has in the past several years aided confirmatory diagnosis for an increasing proportion of patients with genetic neuropathy. Various reports have described associations of Charcot-Marie-Tooth disease with a suspected or confirmed inflammatory neuropathy occasionally responding to immunotherapy. Possible predisposition to an inflammatory component was suggested in a subset of patients. Such reports have, however, been relatively few in number, suggesting the rarity of such associations and of such a predisposition if it exists. There have been a number of publications detailing clinical presentations suggestive of inflammatory neuropathy in patients with a known or later proven genetic aetiology, and subsequently felt to be part of the phenotype rather than representing an association. A number of genetically mediated multisystemic diseases with neuropathy have otherwise been reported as mimicking chronic inflammatory demyelinating polyneuropathy (CIDP). The most common example is that of familial amyloid polyneuropathy, of particular concern for the clinician when misdiagnosed as CIDP, in view of the therapeutic implications. We review the literature on reported associations, mimics and misdiagnoses of hereditary and inflammatory neuropathy and attempt to determine a practical approach to the problem in clinical practice using clinical features, electrophysiology, histopathology and targeted early genetic testing. The issue of attempting immunomodulatory therapy is discussed in view of the published literature.

Transthyretin amyloid neuropathy has earlier neural involvement but better prognosis than primary amyloid counterpart: an answer to the paradox?

OBJECTIVE

To systematically compare transthyretin with primary amyloid neuropathy to define their natural history and the underlying mechanisms for differences in phenotype and natural history.

METHODS

All patients with defined amyloid subtype and peripheral neuropathy who completed autonomic testing and electromyography at Mayo Clinic Rochester between 1993 and 2013 were included. Medical records were reviewed for time of onset of defined clinical features. The degree of autonomic impairment was quantified using the composite autonomic severity scale. Comparisons were made between acquired and inherited forms of amyloidosis.

RESULTS

One hundred one cases of amyloidosis with peripheral neuropathy were identified, 60 primary and 41 transthyretin. Twenty transthyretin cases were found to have Val30Met mutations; 21 had other mutations. Compared to primary cases, transthyretin cases had longer survival, longer time to diagnosis, higher composite autonomic severity scale scores, greater reduction of upper limb nerve conduction study amplitudes, more frequent occurrence of weakness, and later non-neuronal systemic involvement. Four systemic markers (cardiac involvement by echocardiogram, weight loss > 10 pounds, orthostatic intolerance, fatigue) in combination were highly predictive of poor survival in both groups.

INTERPRETATION

These findings suggest that transthyretin has earlier and greater predilection for neural involvement and more delayed systemic involvement. The degree and rate of systemic involvement is most closely related to prognosis. Ann Neurol 2016;80:401-411.

TTR kinetic stabilizers and TTR gene silencing: a new era in therapy for familial amyloidotic polyneuropathies

INTRODUCTION

Transthyretin Familial Amyloid Polyneuropathy (TTR-FAP) is a rare disease with autosomal dominant transmission due to a point mutation of the TTR gene. By removing the main source of systemic mutant TTR, liver transplantation (LT) has become the reference therapy of this severe and fatal polyneuropathy of adult-onset, stopping disease progression in subgroup of patients. Recently, new therapeutic strategies have emerged, which intend to stabilize TTR or to silence the TTR gene. Amongst them, the TTR kinetic stabilizer tafamidis is the first drug approved in the EU.

AREAS COVERED

We shall review the natural history of TTR-FAP and the best indications for LT. Data on the efficacy, safety and tolerability of the TTR kinetic stabilizers, tafamidis and diflunisal, have been reviewed, from the pivotal Phase III clinical trials published in PubMed medical journals or presented at international meetings. We will review the ongoing phase III clinical trials of TTR gene silencing with RNAi therapeutics and ASO published in clinicaltrialgov.

EXPERT OPINION

Due to the data on efficacy, tolerability, safety, tafamidis and diflunisal became the first line anti-amyloid treatment in stage 1 TTR-FAP. Both drugs slow progression of the disease. Only tafamidis got marketing authorization. We are waiting for results of the 2 phase III clinical trials of TTR gene silencing in varied stages of the disease.