Diagnostic hallmarks and pitfalls in late-onset progressive transthyretin-related amyloid-neuropathy

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.

Diagnosis of hereditary transthyretin amyloidosis in patients with suspected chronic inflammatory demyelinating polyneuropathy unresponsive to intravenous immunoglobulins: results of a retrospective study

BACKGROUND AND AIMS

Hereditary transthyretin amyloidosis (ATTRv) should be considered in patients diagnosed with intravenous immunoglobulin (IVIg)-resistant chronic inflammatory demyelinating polyradiculoneuropathy (IVIg-NR CIDP). In this 1-year long, retrospective, multicentric study, an online questionnaire was sent to 1100 French healthcare professionals (HCPs) investigating: (i) how many IVIg-NR CIDP patients they followed; (ii) how many IVIg-NR CIDP patients had undergone TTR gene analysis; and (iii) how many IVIg-NR CIDP patients were eventually diagnosed with ATTRv. The questionnaire was sent every 3 months for 1 year and contained information on ATTRv clinical manifestations and diagnosis.

RESULTS

One-hundred and ten (10%) HCPs responded. A total of 2131 patients with CIDP were identified, including 315 (22.1%) with IVIg-NR CIDP. TTR gene analysis was performed in 144 patients and was positive in 43 cases (29.9%).

CONCLUSIONS

This study demonstrates that ATTRv should be investigated systematically in patients diagnosed with IVIg-NR CIDP. HCP-directed information campaigns are useful for modifying diagnostic practices.

Diagnostic delay in patients with sporadic hereditary transthyretin-mediated amyloidosis

BACKGROUND

Hereditary transthyretin-mediated amyloidosis (ATTRv amyloidosis) is a rare progressively incapacitating condition with a wide range of genotype/phenotype presentations. It is frequently diagnosed late in its course, particularly in sporadic cases.

OBJECTIVES

Analysing predictors of diagnostic delay in this subpopulation should be, therefore, a priority.

METHODS

109 apparently sporadic ATTRv amyloidosis patients followed in a reference centre in Hospital de Santa Maria (ULS Santa Maria-CAML), in Lisbon, were studied. Time from symptom onset to diagnosis, age, sex, municipality of origin and initial symptoms were obtained. Diagnostic delay was compared between different decades with a Kruskal-Wallis test, and its predictors were evaluated in a univariate model followed by a binary logistic regression analysis to calculate the adjusted odds ratio.

RESULTS

The median diagnostic delay was 1262 days. There was a non-significant difference in diagnostic delay between the 80 s, 90 s, 2000s and 2010s decades. There was a non-significant trend for a longer diagnostic delay in woman and in patients having no neurologic symptoms at onset.

CONCLUSION

There is an important diagnostic delay in sporadic cases of ATTRv amyloidosis. Awareness should be spread among clinicians regarding the various manifestations of this disease, stressing the importance of family history and epidemiological data.

Hereditary transthyretin amyloidosis: a comprehensive review with a focus on peripheral neuropathy

Amyloidoses represent a group of diseases characterized by the pathological accumulation in the extracellular area of insoluble misfolded protein material called "amyloid". The damage to the tissue organization and the direct toxicity of the amyloidogenic substrates induce progressive dysfunctions in the organs involved. They are usually multisystem diseases involving several vital organs, such as the peripheral nerves, heart, kidneys, gastrointestinal tract, liver, skin, and eyes. Transthyretin amyloidosis (ATTR) is related to abnormalities of transthyretin (TTR), a protein that acts as a transporter of thyroxine and retinol and is produced predominantly in the liver. ATTR is classified as hereditary (ATTRv) and wild type (ATTRwt). ATTRv is a severe systemic disease of adults caused by mutations in the TTR gene and transmitted in an autosomal dominant manner with incomplete penetrance. Some pathogenic variants in TTR are preferentially associated with a neurological phenotype (progressive peripheral sensorimotor polyneuropathy); others are more frequently associated with restrictive heart failure. However, many mutations express a mixed phenotype with neurological and cardiological involvement. ATTRv is now a treatable disease. A timely and definite diagnosis is essential in view of the availability of effective therapies that have revolutionized the management of affected patients. The purpose of this review is to familiarize the clinician with the disease and with the correct diagnostic pathways in order to obtain an early diagnosis and, consequently, the possibility of an adequate treatment.

Red flags and adjusted suspicion index for distinguishing hereditary transthyretin amyloid polyneuropathy from idiopathic axonal polyneuropathy

BACKGROUND

Early diagnosis of hereditary ATTR polyneuropathy (ATTRv-PN) is important since treatment options have become available, which are most effective early in the disease course. ATTRv-PN is likely underdiagnosed as patients might be misdiagnosed with idiopathic polyneuropathy. It is uncertain if it is useful to test for TTR gene mutations in patients with a typical presentation for chronic idiopathic axonal polyneuropathy (CIAP) and which are the distinguishing clinical features.

METHODS

We carried out a retrospective cohort study to assess the yield of TTR gene sequencing in patients with polyneuropathy and assessed if the identified patients with ATTRv-PN had a clinical presentation typical of CIAP. Additionally, we assessed which clinical features, including previously defined red flag symptoms, can differentiate between patients with CIAP and ATTRv-PN and assessed the performance of the TTR suspicion index.

RESULTS

Out of 338 patients with polyneuropathy, 10 patients had a pathogenic TTR gene mutation (all p.Val50Met) and none had a clinical presentation typical of CIAP. Patients with ATTRv-PN more often had bilateral CTS, motor involvement of arms, cardiac involvement, family history suggestive of hATTRv, and autonomic symptoms than patients with CIAP. All patients with ATTRv-PN as well as 70% of patients with CIAP fulfilled the suspicion index.

CONCLUSION

Routine TTR gene sequencing in patients with a typical presentation for CIAP is not useful. However, red flag symptoms can differentiate patients with ATTRv-PN from patients with CIAP. We propose an adjusted version of the TTR suspicion index to increase diagnostic yield.

A multicentric study of the disease risks and first manifestations in hereditary transthyretin amyloidosis (ATTRv): insights for an earlier diagnosis

BACKGROUND

In hereditary transthyretin amyloidosis (ATTRv), early manifestation and age at onset (AO) may vary strikingly. We assessed the disease'risk (penetrance), AO and initial features in ATTRv families to gain insights on the early disease presentation.

METHODS

Genealogical information, AO and first disease manifestations were collected in ATTRv families, from Sweden, Italy (Sicily), Spain (Mallorca), France, Turkey, Brazil. Penetrance was computed using a non-parametric survival method.

RESULTS

We analysed 258 TTRV30M kindreds and 84 carrying six other variants (TTRT49A, F64L, S77Y, S77F, E89Q, I107V). In ATTRV30M families, the earliest disease risk was found at age 20 years in the Portuguese and Mallorcan families and at age 30-35 years, in the French and Swedish groups. The risks were higher in men and in carriers of maternal descent. In families carrying TTR-nonV30M variants, the earliest disease risk ranged from 30 y-o in TTRT49A to 55 y-o in TTRI107V families. Peripheral neuropathy symptoms were the most frequent initial manifestations. Among patients carrying TTRnonV30M variants, about 25% had an initial cardiac phenotype, one third a mixed phenotype.

CONCLUSION

Our work provided solid data on the risks and early features of ATTRv in a spectrum of families to enhance an early diagnosis and treatment.

Brazilian consensus for diagnosis, management and treatment of hereditary transthyretin amyloidosis with peripheral neuropathy: second edition

Hereditary transthyretin amyloidosis with peripheral neuropathy (ATTRv-PN) is an autosomal dominant inherited sensorimotor and autonomic polyneuropathy with over 130 pathogenic variants identified in the TTR gene. Hereditary transthyretin amyloidosis with peripheral neuropathy is a disabling, progressive and life-threatening genetic condition that leads to death in ∼ 10 years if untreated. The prospects for ATTRv-PN have changed in the last decades, as it has become a treatable neuropathy. In addition to liver transplantation, initiated in 1990, there are now at least 3 drugs approved in many countries, including Brazil, and many more are being developed. The first Brazilian consensus on ATTRv-PN was held in the city of Fortaleza, Brazil, in June 2017. Given the new advances in the area over the last 5 years, the Peripheral Neuropathy Scientific Department of the Brazilian Academy of Neurology organized a second edition of the consensus. Each panelist was responsible for reviewing the literature and updating a section of the previous paper. Thereafter, the 18 panelists got together virtually after careful review of the draft, discussed each section of the text, and reached a consensus for the final version of the manuscript.

Functional and morphometric assessment of small-fibre damage in late-onset hereditary transthyretin amyloidosis with polyneuropathy: the controversial relation between small-fibre-related symptoms and diagnostic test findings

INTRODUCTION

We aimed at investigating whether functional and morphometric tests assessing small-fibre damage, ie quantitative sensory testing, Sudoscan and skin biopsy, reliably reflect neuropathic pain and autonomic symptoms in patients with late-onset hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN).

METHODS

In 30 patients with late-onset ATTRv-PN, we collected quantitative sensory testing, Sudoscan and skin biopsy with assessment of intraepidermal, piloerector muscle and sweat gland nerve fibre density. We then correlated these functional and morphometric parameters with neuropathic pain and autonomic symptoms as assessed with the Neuropathic Pain Symptom Inventory (NPSI) and Composite Autonomic Symptom Score-31 (COMPASS-31).

RESULTS

50% of patients showed small-fibre damage in the form of a pure small-fibre neuropathy, 47% in the context of a mixed fibre neuropathy with small and large fibre involvement. All patients complained of at least one autonomic symptom and 60% had neuropathic pain. Whereas quantitative sensory testing and Sudoscan parameters correlated with neuropathic pain and autonomic symptoms as assessed by NPSI and COMPASS-31, intraepidermal, piloerector muscle and sweat gland nerve fibre density quantification did not.

CONCLUSIONS

Our findings indicate that functional test parameters reliably reflect neuropathic pain and autonomic symptoms related to small-fibre damage. These findings might help to identify clinically useful biomarkers to assess patient follow-up.

A retrospective survey of patients with hereditary transthyretin-mediated (hATTR) amyloidosis treated with patisiran in real-world clinical practice in Belgium

INTRODUCTION

Hereditary transthyretin-mediated (hATTR) amyloidosis, a genetic disease caused by mutations in the transthyretin gene, leads to progressive sensory and autonomic neuropathy and/or cardiomyopathy and is associated with renal and ophthalmologic manifestations and a poor prognosis.

METHODS

This is a retrospective study based on data collected from the medical records of patients with hATTR amyloidosis treated with patisiran between 01 July 2018 and 01 February 2021. Six Belgian neuromuscular reference centers participated, covering all patisiran-treated hATTR amyloidosis patients at the study time. This study was conducted to collect data requested in the context of the reimbursement of patisiran in Belgium.

RESULTS

Thirty-one patients were diagnosed with hATTR amyloidosis with polyneuropathy, Coutinho stage 1 or 2, and eligible for active treatment during the data collection period. Of the hATTR amyloidosis patients treated with patisiran (n = 12), seven and five had polyneuropathy stages 1 and 2, respectively. Six patients had cardiac symptoms (New York Heart Association class 2 or above). Follow-up information was available for nine patients. Following patisiran treatment, eight patients showed stable or improved assessments for most neurological or cardiological parameters. Only one patient presented with worsening statuses at the end of the data collection period.

CONCLUSIONS

The patients with hATTR amyloidosis in Belgium have similar baseline demographics and disease characteristics to those studied in the patisiran APOLLO study and show a similar therapeutic response in the real-world, altering the expected disease progression in most patients.

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.

Unique Phenotypes With Corresponding Pathology in Late-Onset Hereditary Transthyretin Amyloidosis of A97S vs. V30M

Objective

Hereditary transthyretin amyloidosis (ATTRv) encompasses different phenotypes among various genotypes. The analysis of the natural history and risk factors of faster progression in different genotypes would refine the treatment strategy.

Methods

The clinical manifestations of ATTRv from A97S (p.A117S) of Taiwanese and late-onset V30M (p.V50M) of Japanese were compared. An autopsy study of A97S was performed.

Results

There existed three unique features in the A97S cohort compared to the V30M cohort: (1) dysphagia, (2) carpal tunnel syndrome (CTS), and (3) onset age. First, dysphagia was common in A97S (53.4%) but not in V30M and served as a contributor to fast disease progression. All phases of swallowing were affected. In the autopsy pathology, there were extensive amyloid deposits in the viscera and nerves of the tongue, larynx, and esophagus. In A97S, 45 patients (43.3%) had a history of CTS before the onset of length-dependent symptoms by 3 years. The amyloid deposition was more prominent in the median nerve than that in the transverse carpal ligament. The onset age at different stages was younger in the A97S cohort than the V30M cohort by 4–5 years.

Conclusion

These phenotypic characteristics together with autopsy pathology in A97S are distinct from V30M. Early dysphagia in A97S correlated with fast progression. In A97S, median neuropathy leading to CTS might be in a continuous spectrum of ATTRv course rather than an independent disease entity. Such observations may serve as a foundation to explore and analyze unique phenotypes among various genotypes.

Vagus nerve ultrasound in transthyretin familial amyloid polyneuropathy: A pilot study

BACKGROUND AND PURPOSE

Autonomic dysfunction is common in transthyretin familial amyloid polyneuropathy (TTR-FAP). Because ultrasonography is a powerful tool to study peripheral neuropathy, vagus nerve (VN) ultrasonography was used in our study to investigate the possible changes of the dimension of VN in TTR-FAP.

METHODS

Eighteen patients with TTR-FAP and 17 age- and gender-matched individuals without any neuropathies were enrolled in a pilot study. The cross-sectional areas (CSAs) were measured bilaterally on transverse scans of vagus, median, and ulnar nerves. Clinical data were collected to explore the correlations with CSAs of VN.

RESULTS

The median CSAs of VN in TTR-FAP were 3.5 (2.0-6.0) mm² on the right side and 2.5 (1.0-6.0) mm² on the left side, compared with 2.0 (1.0-3.0) mm² and 1.0 (1.0-2.0) mm² for healthy controls (HCs). There was a significant difference between the two groups on both sides (p < .001). The mean VN CSAs were correlated positively with the course of disease (r = .7203, p = .0016)（not including the patient with the longest disease course), the Composite Autonomic Symptom Score 31 (r = .5252, p = .0252), the left ventricular posterior wall thickness (r = .5426, p = .0200), and the interventricular septum thickness (r = .5103, p = .0305). The cutoff values of right and left VN CSAs to identify TTR-FAP from HCs were 2.5 and 1.5 mm² and the areas under the curve were .9395 and .8856, with a high sensitivity (.889 and .889) and specificity (.941 and .765), respectively.

CONCLUSION

VN enlargement is prevalent among TTR-FAP patients. VN ultrasonography may be an important clinical tool for assessing the severity of autonomic dysfunction in TTR-FAP.

Variable Presentation of Hereditary Transthyretin-Mediated Amyloidosis at a Single Center

OBJECTIVES

Describe atypical presentations of hereditary transthyretin-mediated (hATTR) amyloidosis with polyneuropathy.

METHODS

Initial symptoms, diagnoses, and follow-up were recorded at the Austin Neuromuscular Center for 12 patients with nonclassical presentation of hATTR amyloidosis.

RESULTS

Common initial symptoms were hand and/or feet sensory manifestations (83%), muscle weakness (58%), and, less frequently, gastrointestinal and orthostatic impairment and carpal tunnel syndrome. Initial diagnoses were polyneuropathy (83%) and/or myopathy (25%). During follow-up, 10 patients (83%) developed cardiac symptoms (dyspnea, 67% and ankle edema, 17%), resulting in revised diagnoses of heart disease. Multisystem involvement raised suspicion of amyloidosis, which was confirmed by biopsy or nuclear scintigraphy, and genetic testing. All patients had polyneuropathy; 8 (67%) had cardiomyopathy-associated transthyretin mutations (V122I or T60A). Time from symptom onset to diagnosis was up to 10 years (median 5 years), during which patients' health deteriorated, although with recognition of disease signs/symptoms the diagnosis of hATTR amyloidosis was made in approximately 2-6 months from presentation at our center.

CONCLUSIONS

Increased awareness of the diverse initial hATTR amyloidosis symptoms could shorten time to diagnosis, enabling earlier treatment and improved patient outcomes.

Hereditary Transthyretin Amyloidosis- Clinical and Genetic Characteristics of a Multiracial South-East Asian Cohort in Singapore

BACKGROUND AND AIMS

Studies of hereditary transthyretin amyloidosis (ATTRv amyloidosis) in South-East Asia are underrepresented in the literature. We report the unique phenotypic and genetic characteristics of this disorder in a multiracial South-East Asian cohort.

METHODS

Patients with genetically proven ATTRv amyloidosis were identified over a 13-year period (2007-2020) at the National Neuroscience Institute, Singapore. Clinical, laboratory, genotypic and electrophysiological features were retrospectively reviewed.

RESULTS

29 patients comprising Chinese, Malay, Burmese, Vietnamese and Indonesians with ATTRv amyloidosis were identified. Somatic neuropathy was the most common initial presentation, followed by carpal tunnel syndrome, autonomic dysfunction and cardiac dysfunction. ATTR-A97S (p.Ala117Ser) was the most common variant found in 14 patients, constituting 66.7%of ethnic Chinese patients and 48.3%of the entire cohort. Five patients had early-onset disease (age < 50 years) with the following variants: ATTR-V30M (p.Val50Met), ATTR-G47A (p.Gly67Ala), ATTR-S50I (p.Ser70Ile) and ATTR-A97S (p.Ala117Ser); one patient with ATTR-A97S (p.Ala117Ser) had isolated unilateral carpal tunnel syndrome with amyloid deposits identified on histological examination of the transverse carpal ligament. All early-onset patients had a positive parental history; two patients, with ATTR-S50I (p.Ser70Ile) and ATTR-Ala97Ser (p.Ala117Ser) respectively, demonstrated anticipation with mother-to-daughter inheritance. Amongst the 24 patients with late-onset disease (age≥50 years), two patients had novel variants, ATTR-G66D (p.Glu86Asp) and ATTR-A81V (p.Ala101Val) that were confirmed to be pathogenic based on the histological identification of transthyretin amyloid. Other identified variants included ATTR-V30M (p.Val50Met), ATTR-R34T (p.Arg54Thr), ATTR-S50I (p.Ser70Ile), ATTR-H88R (p.His108Arg) and ATTR-A97S (p.Ala117Ser).

CONCLUSION

Our study further expands the genotypic and phenotypic knowledge regarding ATTRv amyloidosis.

Val50Met hereditary transthyretin amyloidosis: not just a medical problem, but a psychosocial burden

BACKGROUND

Hereditary transthyretin (TTR) amyloidosis (ATTRv) is a heterogeneous disease with a clinical presentation that varies according to geographical area and TTR mutation. The symptoms of Val50Met-ATTRv are mainly neuropathic and progress to complete disability and death in most untreated patients within 10 to 15 years of diagnosis. The neurological effects may also be accompanied by gastrointestinal impairment, cardiomyopathy, nephropathy and/or ocular deposition. The disease is thus associated with a high degree of patient disability. Accordingly, we aimed to describe the psychosocial burden associated with ATTRv in a group of patients, asymptomatic Val50Met carriers, relatives and caregivers in the endemic focus of the disease in Majorca via a survey addressing various aspects related to psychosocial burden. We performed a an observational, descriptive, cross-sectional and multicentre study in order to analyze the prevalence of self-reported impact of ATTRv disease upon their daily life. In addition to the self-knowledge, fear and burden related to the disease. The survey was disseminated during the regular follow up at the outpatient clinic of the Hospital Universitario Son Llàtzer and during the meetings organized by the Andrade's Disease patients' advocacy group from the Balearic Islands. These meetings were attended also by subjects followed up by the Hospital Universitario Son Espases and their caregivers and relatives. Survey was self-administrated. No intervention was done by the investigators. 85 subjects completed the survey: 61 carrying the TTR-V50M variant and 24 caregivers or relatives.

RESULTS

Our study revealed that, although most of the population studied had had prior contact with ATTRv through affected relatives, there was still a lack of information regarding disease diagnosis. Fear of the genetic test result and psychological issues were common in our population. Moreover, the disease had a stronger impact on the daily life of our patients than that of our asymptomatic carriers. Autonomic symptoms were the main source of burden for relatives and caregivers.

CONCLUSION

Our survey results show high psychosocial burden associated with Val50Met-ATTRv in our area.

Stellenwert klinischer, funktioneller und bildgebender Diagnostik zur Früherkennung, Differenzialdiagnose und Verlaufskontrolle diabetischer Neuropathien

Von weltweit mehr als 400 Mio. Menschen mit Diabetes mellitus entwickeln bis zu 50% im Laufe ihrer Erkrankung eine Neuropathie. Trotz oder gerade wegen dieser Häufigkeit darf jedoch nicht jede Neuropathie, die in Koinzidenz mit einem Diabetes mellitus auftritt, unkritisch als diabetische Neuropathie diagnostiziert werden. Eine präzise Ausschluss- und Ausmaßdiagnostik ist entscheidend, um andere behandelbare Erkrankungen wie z. B. die Chronisch Inflammatorische Demyelinisierende Polyradikuloneuropathie oder die hereditäre Transthyretin-Amyloidose nicht zu übersehen. Einfache, nicht-invasive, preiswerte und allzeit verfügbare Screeningmethoden stellen Anamnese und klinische Untersuchung dar. Ergänzend ist in frühen Erkrankungsstadien die Quantitativ Sensorische Testung hilfreich zur Eingrenzung einer Small Fiber-Dysfunktion. Sind, typischerweise im Verlauf, große Nervenfasern geschädigt, so ist das charakteristische elektrophysiologische Bild das einer längenabhängigen, axonalen, sensibel betonten oder sensomotorischen Neuropathie. Die Nervensonografie kann zur Unterscheidung von autoimmun-demyelinisierenden Neuropathien hilfreich sein. Moderne Untersuchungsverfahren wie die MR-Neurografie können auch proximale Nervenabschnitte bis auf Faszikelebene darstellen, sind allerdings nur an wenigen Zentren verfügbar. Haut- und Nervenbiopsien sind v. a. bei untypischen Verläufen zur Abgrenzung von Differenzialdiagnosen hilfreich. Diabetische Neuropathien können zu einer erheblichen Reduktion von Lebensqualität und Lebensdauer führen. Zur frühest- und bestmöglichen ursächlichen und symptomatischen Therapieeinleitung ist eine präzise Diagnostik essentiell.

Targeting transthyretin - Mechanism-based treatment approaches and future perspectives in hereditary amyloidosis

The liver-derived, circulating transport protein transthyretin (TTR) is the cause of systemic hereditary (ATTRv) and wild-type (ATTRwt) amyloidosis. TTR stabilization and knockdown are approved therapies to mitigate the otherwise lethal disease course. To date, the variety in phenotypic penetrance is not fully understood. This systematic review summarizes the current literature on TTR pathophysiology with its therapeutic implications. Tetramer dissociation is the rate-limiting step of amyloidogenesis. Besides destabilizing TTR mutations, other genetic (RBP4, APCS, AR, ATX2, C1q, C3) and external (extracellular matrix, Schwann cell interaction) factors influence the type of onset and organ tropism. The approved small molecule tafamidis stabilizes the tetramer and significantly decelerates the clinical course. By sequence-specific mRNA knockdown, the approved small interfering RNA (siRNA) patisiran and antisense oligonucleotide (ASO) inotersen both significantly reduce plasma TTR levels and improve neuropathy and quality of life compared to placebo. With enhanced hepatic targeting capabilities, GalNac-conjugated siRNA and ASOs have recently entered phase III clinical trials. Bivalent TTR stabilizers occupy both binding groves in vitro, but have not been tested in trials so far. Tolcapone is another stabilizer with the potential to cross the blood-brain barrier, but its half-life is short and liver failure a potential side effect. Amyloid-directed antibodies and substances like doxycycline aim at reducing the amyloid load, however, none of the yet developed antibodies has successfully passed clinical trials. ATTR-amyloidosis has become a model disease for pathophysiology-based treatment. Further understanding of disease mechanisms will help to overcome the remaining limitations, including application burden, side effects, and blood-brain barrier permeability.

Anticipation on age at onset in kindreds with hereditary ATTRV30M amyloidosis from the Majorcan cluster

BACKGROUND

Hereditary transthyretin amyloidosis (ATTRV30M) is a rare disease caused by amyloid deposition and characterized by a heterogeneous presentation. Anticipation (AC) is described as the decrease in age at onset (AO) within each generation. Our aim was to study AC in a large number of ATTRV30M kindred from Majorca (Spain), and gain further insight into parent-of-origin effects.

METHODS

In a cohort of 262 subjects with ATTRV30M amyloidosis belonging to 51 families, we found 37 affected pairs. AO is defined as the age at the first symptom and AC (parent's age at disease onset minus that of the offspring) were calculated. Chi-square test, independent t-test and paired t-test were used for comparisons between groups. Association between AO of parents and offsprings were assessed by Pearson's correlation coefficient.

RESULTS

Offspring mean AO was 16 years lower than that of the parents (p < .001) regardless of the sex of the parents and the offspring. AC occurred in 31 out of the 37 pairs, with no differences related to the sex of parents or offspring. There was a moderate correlation (r = 0.49; p < .001) between AO of the parents and that of the offsprings.

CONCLUSION

AC was no uncommon in our cohort, and AO tended to decrease in successive generations.

Tetraparesis and sensorimotor axonal polyneuropathy due to co-occurrence of Pompe disease and hereditary ATTR amyloidosis

INTRODUCTION/AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (hATTRPN) is an autosomal dominant multi-organ disorder manifesting in the third to fifth decade with the key clinical features of distal and painful sensory loss of the lower limbs and autonomic dysregulation. Motor neuropathy and cardiomyopathy evolve in the course of the disease. Pompe disease is an autosomal recessive disease leading to decreased levels of lysosomal enzyme acid α-glucosidase and proximal muscle weakness. We report the clinical features and diagnostic workup in the rare case of a patient with ATTR amyloidosis and late-onset Pompe disease, both genetically confirmed.

METHODS

We performed a detailed clinical assessment, exome sequencing, and biochemical measurements.

RESULTS

The patient presented with a distal, painful hypaesthesia of both legs, a cardiomyopathy, and a muscle weakness in the form of a girdle-type pattern of the arms and legs at the beginning and a spreading to distal muscle groups in the course of disease.

DISCUSSION

This study highlights the importance of searching for co-occurrence of rare monogenetic neuromuscular diseases, especially in cases in which all clinical features can be readily explained by a single gene defect.

Excisional goniotomy with Kahook Dual Blade in a patient with glaucoma secondary to Transthyretin Amyloidosis

PURPOSE

To report for the first time the successful use of the Kahook Dual Blade excisional goniotomy technique in a patient with Transthyretin Amyloidosis.

PATIENT AND METHODS

The Kahook Dual Blade is a single use ab interno trabeculectomy device that removes the trabecular meshwork reducing aqueous humor outflow resistance. A patient with Transthyretin Amyloidosis underwent this procedure.

RESULTS

Ab interno goniotomy with Kahook Dual Blade was a successful surgical solution to reduce intraocular pressure in a patient with Transthyretin Amyloidosis secondary glaucoma controlling IOP in association with topical hypotensors for at least 6 months.

CONCLUSIONS

Ab interno goniotomy with Kahook Dual Blade is a surgical option for this type of glaucoma, that treats the main site of aqueous outflow resistance in this pathology with the advantage of being minimally invasive.

Diagnosis and Treatment of Hereditary Transthyretin Amyloidosis (hATTR) Polyneuropathy: Current Perspectives on Improving Patient Care

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy) is a rare disease due to mutations in the gene encoding transthyretin (TTR) and characterized by multisystem extracellular deposition of amyloid, leading to dysfunction of different organs and tissues. hATTR amyloidosis represents a diagnostic challenge for neurologists considering the great variability in clinical presentation and multiorgan involvement. Generally, patients present with polyneuropathy, but clinicians should consider the frequent cardiac, ocular and renal impairment. Especially a hypertrophic cardiomyopathy, even if usually latent, is identifiable in at least 50% of the patients. Therapeutically, current available options act at different stages of TTR production, including synthesis inhibition (liver transplantation and/or gene-silencing drugs) or tetramer TTR stabilization (TTR stabilizers), increasing survival at different disease stages.

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Expert consensus recommendations to improve diagnosis of ATTR amyloidosis with polyneuropathy

Amyloid transthyretin (ATTR) amyloidosis with polyneuropathy (PN) is a progressive, debilitating, systemic disease wherein transthyretin protein misfolds to form amyloid, which is deposited in the endoneurium. ATTR amyloidosis with PN is the most serious hereditary polyneuropathy of adult onset. It arises from a hereditary mutation in the TTR gene and may involve the heart as well as other organs. It is critical to identify and diagnose the disease earlier because treatments are available to help slow the progression of neuropathy. Early diagnosis is complicated, however, because presentation may vary and family history is not always known. Symptoms may be mistakenly attributed to other diseases such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), idiopathic axonal polyneuropathy, lumbar spinal stenosis, and, more rarely, diabetic neuropathy and AL amyloidosis. In endemic countries (e.g., Portugal, Japan, Sweden, Brazil), ATTR amyloidosis with PN should be suspected in any patient who has length-dependent small-fiber PN with autonomic dysfunction and a family history of ATTR amyloidosis, unexplained weight loss, heart rhythm disorders, vitreous opacities, or renal abnormalities. In nonendemic countries, the disease may present as idiopathic rapidly progressive sensory motor axonal neuropathy or atypical CIDP with any of the above symptoms or with bilateral carpal tunnel syndrome, gait disorders, or cardiac hypertrophy. Diagnosis should include DNA testing, biopsy, and amyloid typing. Patients should be followed up every 6–12 months, depending on the severity of the disease and response to therapy. This review outlines detailed recommendations to improve the diagnosis of ATTR amyloidosis with PN.

Inflammatory profiling of patients with familial amyloid polyneuropathy

BACKGROUND

Familial amyloid polyneuropathy (FAP) or ATTRv (amyloid TTR variant) amyloidosis is a fatal hereditary disease characterized by the deposition of amyloid fibrils composed of transthyretin (TTR). The current diagnosis of ATTRv relies on genetic identification of TTR mutations and on Congo Red-positive amyloid deposits, which are absent in most ATTRv patients that are asymptomatic or early symptomatic, supporting the need for novel biomarkers to identify patients in earlier disease phases allowing disease control.

METHODS

In an effort to search for new markers for ATTRv, our group searched for nine inflammation markers in ATTRv serum from a cohort of 28 Brazilian ATTRv patients.

RESULTS

We found that the levels of six markers were increased (TNF-α, IL-1β, IL-8, IL-33, IFN-β and IL-10), one had decreased levels (IL-12) and two of them were unchanged (IL-6 and cortisol). Interestingly, asymptomatic patients already presented high levels of IL-33, IL-1β and IL-10, suggesting that inflammation may take place before fibril deposition.

CONCLUSIONS

Our findings shed light on a new, previously unidentified aspect of ATTRv, which might help define new criteria for disease management, as well as provide additional understanding of ATTRv aggressiveness.

Hereditary transthyretin amyloidosis: a model of medical progress for a fatal disease

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis with polyneuropathy (also known as familial amyloid polyneuropathy) is a condition with adult onset caused by mutation of transthyretin (TTR) and characterized by extracellular deposition of amyloid and destruction of the somatic and autonomic PNS, leading to loss of autonomy and death. This disease represents a model of the scientific and medical progress of the past 30 years. ATTRv amyloidosis is a worldwide disease with broad genetic and phenotypic heterogeneity that presents a diagnostic challenge for neurologists. The pathophysiology of the neuropathy is increasingly understood and includes instability and proteolysis of mutant TTR leading to deposition of amyloid with variable lengths of fibrils, microangiopathy and involvement of Schwann cells. Wild-type TTR is amyloidogenic in older individuals. The main symptoms are neuropathic, but the disease is systemic; neurologists should be aware of cardiac, eye and kidney involvement that justify a multidisciplinary approach to management. Infiltrative cardiomyopathy is usually latent but present in half of patients. Disease-modifying therapeutics that have been developed include liver transplantation and TTR stabilizers, both of which can slow progression of the disease and increase survival in the early stages. Most recently, gene-silencing drugs have been used to control disease in the more advanced stages and produce some degree of improvement.

New sequence variants in patients affected by amyloidosis show transthyretin instability by isoelectric focusing

The plasma protein transthyretin (TTR) can aggregate into insoluble amyloid fibrils causing systemic amyloidosis (ATTR amyloidosis) in patients carrying a variant TTR protein. If new variants arise, it is crucial to clarify whether they are disease-associated or benign. In this study, we further functionally characterize three new and unclassified TTR variants (Thr40Asn, Phe64Val and the described but not functionally assessed variant Leu12Val), using a simplified, fast isoelectric focusing (IEF) approach. After validating the system with known TTR variants, we assessed the sera of five patients carrying these new TTR variants in a heterozygous state. All three variants showed aberrant banding patterns that were similar to those of other well-characterized TTR variants, including the common Val30Met variant that causes ATTR amyloidosis. In addition to a clear band corresponding to monomeric wild-type TTR, we observed an additional variant band at the cathodal side of the IEF gel. These results indicate conformational instability of the new Thr40Asn, Phe64Val and Leu12Val variants. Together with the clinical and immunohistological data of these patients and affected family members, as well as the absence of these variants in human genetic mutation databases, our results strongly hint that these variants are amyloidogenic and therefore probably disease-associated. These findings have implications for patient therapy and for genetic counselling of family members.

Late-onset hereditary ATTR V30M amyloidosis with polyneuropathy: Characterization of Brazilian subjects from the THAOS registry

BACKGROUND

Despite growing numbers of patients diagnosed with late-onset hereditary ATTR V30M amyloidosis with polyneuropathy (ATTRv-PN), this condition remains poorly characterized in Brazil.

OBJECTIVE

Characterize late-onset V30M ATTRv-PN in Brazil.

MATERIAL AND METHODS

Demographic and clinical data at the time of enrolment for Brazilian subjects with symptomatic V30M ATTRv-PN were extracted from the ongoing, multinational, longitudinal, observational Transthyretin Amyloidosis Outcomes Survey (THAOS; cut-off date: January 30, 2017). Subjects were divided into those with symptom onset at age <50 years (EO-V30M), and at age ≥50 years (LO-V30M).

RESULTS

A total of 96 Val30Met patients were symptomatic. LO-V30M (n = 25, 26.0%) had a longer time to diagnosis (mean 5.1 vs. 2.8 yrs.; p = 0.006) and less frequently positive family history (40% vs. 95.8%; p < 0.0001) than EO-V30M. Clinically, subjects with LO-V30M had more imbalance (92% vs. 54.9%; p = 0.006), deep sensory loss (100% vs. 80%; p = 0.0178), electrocardiogram abnormalities (88.9% vs. 59.4; p = 0.0241), and interventricular septum hypertrophy (69.2% vs. 0%; p < 0001) and less frequently sensory dissociation (12% vs. 74%; p < 0.0001). Also, LO-V30M tended to have more severe mean Neurologic Composite Score (101 vs. 70 pts.; p = 0.1136).

CONCLUSIONS

LO-V30M ATTRv-PN is not unusual in Brazil, tending to be more difficult to diagnose and present with a more severe phenotype, with more large nerve fibers and cardiac involvement than EO-V30M.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00628745.

Brazilian consensus for diagnosis, management and treatment of transthyretin familial amyloid polyneuropathy

Transthyretin familial amyloid polyneuropathy is an autosomal dominant inherited sensorimotor and autonomic polyneuropathy, which if untreated, leads to death in approximately 10 years. In Brazil, liver transplant and tafamidis are the only disease-modifying treatments available. This review consists of a consensus for the diagnosis, management and treatment for transthyretin familial amyloid polyneuropathy from the Peripheral Neuropathy Scientific Department of the Brazilian Academy of Neurology. The first and last authors produced a draft summarizing the main views on the subject and emailed the text to 10 other specialists. Relevant literature on this subject was reviewed by each participant and used for the individual review of the whole text. Each participant was expected to review the text and send a feedback review by e-mail. Thereafter, the 12 panelists got together at the city of Fortaleza, discussed the controversial points, and reached a consensus for the final text.

Hereditary transthyretin-related amyloidosis

Hereditary transthyretin(TTR)-related amyloidosis (ATTRm amyloidosis) is an endemic/non-endemic, autosomal-dominant, early- and late-onset, rare, progressive disorder, predominantly manifesting as length-dependent, small fiber dominant, axonal polyneuropathy and frequently associated with cardiac disorders and other multisystem diseases. ATTRm amyloidosis is due to variants in the TTR gene, with the substitution Val30Met as the most frequent mutation. TTR mutations lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, and formation of amyloid fibrils, which are consecutively deposited extracellularly in various tissues, such as nerves, heart, brain, eyes, intestines, kidneys, or the skin. Neuropathy may not only include large nerve fibers but also small fibers, and not only sensory and motor fibers but also autonomic fibers. Types of TTR variants, age at onset, penetrance, and clinical presentation vary between geographical areas. Suggestive of a ATTRm amyloidosis are a sensorimotor polyneuropathy, positive family history, autonomic dysfunction, cardiomyopathy, carpal tunnel syndrome, unexplained weight loss, and resistance to immunotherapy. If only sensory A-delta or C fibers are affected, small fiber neuropathy ensues. Diagnostic tests for small fiber neuropathy include determination of intraepidermal nerve fiber density, laser-evoked potentials, heat- and cold-detection thresholds, and measurement of the electrochemical skin conductance. Therapy currently relies on liver transplantation and TTR-stabilizers (tafamidis, diflunisal).

[Neuropathic pain syndromes and channelopathies]

BACKGROUND

The causes for neuropathic pain are manifold and remain unexplained in the majority of cases. In recent years a growing number of pain syndromes have been attributed to mutations in genes encoding voltage-gated sodium channels. Hence, this group of rare diseases should be considered in the differential diagnostics of neuropathic pain.

MATERIAL AND METHODS

Evaluation of topic-related literature and discussion of own experiences as well as consideration of current guidelines.

RESULTS

Alterations in the electrical excitability of nociceptive neurons by pathogenic mutations in sodium channels lead to disease patterns, such as small fiber neuropathy and various pain syndromes. This article summarizes the knowledge on these genetic diseases and discusses the differential diagnosis of neuropathic pain. Current treatment concepts are presented and the predominantly experimental approaches to targeted modulation of sodium channels are discussed.

CONCLUSION

The treatment of patients with chronic neuropathic pain requires interdisciplinary cooperation and is often difficult due to an unsatisfactory treatment response. Increasing knowledge on rare genetically determined channelopathies can contribute to the development of novel pharmaceuticals since ion channels are central players in the processing of pain.

[Transthyretin familial amyloid polyneuropathy]

Transthyretin family amyloid polyneuropathy (TTR-FAP) is a progressive, ultimately fatal disease. It manifests itself primarily with sensory, motor and autonomic polyneuropathy and/or cardiomyopathy and is caused by extracellular deposition of insoluble amyloid fibrils in the endoneurium. The cause of TTR-FAP is the mutation in the gene encoding transthyretin, more than 100 types of mutations are known. Given the phenotypic diversity of TTR-FAP, it is difficult for clinicians to make this diagnosis. An erroneous diagnosis is a frequent occurrence, risking the onset of an organ pathology. The paper addresses the issues of the pathogenesis, diagnosis and treatment of TTR-FAP.

Autosomal-dominant transthyretin (TTR)-related amyloidosis is not a frequent CMT2 neuropathy "in disguise"

Transthyretin (TTR)-related familial amyloid polyneuropathy (TTR-FAP) is a life-threatening autosomal dominant, systemic disease. First symptoms usually occur from the second to over sixth decade of life with a length-dependent axonal neuropathy with prominent involvement of the small fibers and multi-organ systemic failure.

Early diagnosis is pivotal for effective therapeutic options, but it is hampered by the heterogeneity of the clinical spectrum which can lead to misdiagnosis with other neurological condition/disorder such as axonal sensory-motor neuropathy (CMT2) as described in literature.

The aim of our study was to search for TTR mutations in a large cohort of selected undiagnosed axonal sensory-motor neuropathy patients to establish if misdiagnosis is frequent or rare in the Italian population.

No TTR pathogenic variants were found in our cohort. In conclusion, our study shows that TTR testing not should be straightforward recommended in CMT2 patients but only when “red flags” TTR’s features are present.

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.

Phenotypic expressions of hereditary Transthyretin Ala97Ser related Amyloidosis (ATTR) in Taiwanese

Background

The disease course and early signs specific to ATTR Ala97Ser, the most common endemic mutation in Taiwan, have not been well described. Since new medications can slow down the rate of disease progression, the early diagnosis of this heterogeneous and fatal disease becomes critical.

Methods

We retrospectively reviewed the characteristics of genetically confirmed ATTR Ala97Ser patients at a tertiary referral medical center.

Results

Eight patients from 7 different families were enrolled (61.7 ± 5.5 years). Gastrointestinal symptoms, dyspnea or chest tightness, rather than sensory symptoms, were the initial symptoms in two patients (2/7 = 29%). Body weight loss (3/7 = 43%), muscle wasting (4/7 = 57%), or dysphagia (3/7 = 43%) were the consecutive symptoms. Orthostatic symptoms including orthostatic hypotension (7/7 = 100%), dizziness (6/7 = 86%) and syncope (5/7 = 71%) tended to develop in the late phase of the disease. Autonomic dysfunction was conspicuous. Cardiographic findings included a combination of ventricular wall thickening and pericardial effusion (7/7 = 100%), a granular sparkling appearance of the ventricular myocardium (4/7 = 57%), or conduction abnormalities (5/7 = 71%).

Conclusions

This study broadens the recognition of the initial signs and symptoms, including cardiographic findings and longitudinal manifestations in Taiwanese individuals with ATTR Ala97Ser mutation. These manifestations should prompt doctors to perform further studies and make an early diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s12883-017-0957-4) contains supplementary material, which is available to authorized users.

Assessing mNIS+7Ionis and international neurologists' proficiency in a familial amyloidotic polyneuropathy trial

INTRODUCTION

Polyneuropathy signs (Neuropathy Impairment Score, NIS), neurophysiologic tests (m+7_Ionis ), disability, and health scores were assessed in baseline evaluations of 100 patients entered into an oligonucleotide familial amyloidotic polyneuropathy (FAP) trial.

METHODS

We assessed: (1) Proficiency of grading neurologic signs and correlation with neurophysiologic tests, and (2) clinometric performance of modified NIS+7 neurophysiologic tests (mNIS+7_Ionis ) and its subscores and correlation with disability and health scores.

RESULTS

The mNIS+7_Ionis sensitively detected, characterized, and broadly scaled diverse polyneuropathy impairments. Polyneuropathy signs (NIS and subscores) correlated with neurophysiology tests, disability, and health scores. Smart Somatotopic Quantitative Sensation Testing of heat as pain 5 provided a needed measure of small fiber involvement not adequately assessed by other tests.

CONCLUSIONS

Specially trained neurologists accurately assessed neuropathy signs as compared to referenced neurophysiologic tests. The score, mNIS+7_Ionis , broadly detected, characterized, and scaled polyneuropathy abnormality in FAP, which correlated with disability and health scores. Muscle Nerve 56: 901-911, 2017.

Genome-wide association analysis in dogs implicates 99 loci as risk variants for anterior cruciate ligament rupture

Anterior cruciate ligament (ACL) rupture is a common condition that can be devastating and life changing, particularly in young adults. A non-contact mechanism is typical. Second ACL ruptures through rupture of the contralateral ACL or rupture of a graft repair is also common. Risk of rupture is increased in females. ACL rupture is also common in dogs. Disease prevalence exceeds 5% in several dog breeds, ~100 fold higher than human beings. We provide insight into the genetic etiology of ACL rupture by genome-wide association study (GWAS) in a high-risk breed using 98 case and 139 control Labrador Retrievers. We identified 129 single nucleotide polymorphisms (SNPs) within 99 risk loci. Associated loci (P<5E-04) explained approximately half of phenotypic variance in the ACL rupture trait. Two of these loci were located in uncharacterized or non-coding regions of the genome. A chromosome 24 locus containing nine genes with diverse functions met genome-wide significance (P = 3.63E-0.6). GWAS pathways were enriched for c-type lectins, a gene set that includes aggrecan, a gene set encoding antimicrobial proteins, and a gene set encoding membrane transport proteins with a variety of physiological functions. Genotypic risk estimated for each dog based on the risk contributed by each GWAS locus showed clear separation of ACL rupture cases and controls. Power analysis of the GWAS data set estimated that ~172 loci explain the genetic contribution to ACL rupture in the Labrador Retriever. Heritability was estimated at 0.48. We conclude ACL rupture is a moderately heritable highly polygenic complex trait. Our results implicate c-type lectin pathways in ACL homeostasis.

Iatrogenic amyloid polyneuropathy after domino liver transplantation

Liver transplantation has been used in treatment of transthyretin amyloidosis, and some patients undergo domino liver transplantation (DLT) with explanted liver being transplanted to another patient with liver failure as the liver is otherwise usually functionally normal. Until end of 2015, there were 1154 DLT performed worldwide. DLT for transthyretin amyloidosis is associated with the risk of developing de novo systemic amyloidosis and amyloid neuropathy, and the risk may be greater with some non-Val30Met mutations. De novo amyloid neuropathy has been described in up to 23% of transplant recipients. Neuropathy may be preceded by asymptomatic amyloid deposition in various tissues and symptoms of neuropathy started after a median of 7 years following DLT (5.7 ± 3.2 years; range 2 mo to 10 years). Typical initial symptoms include neuropathic pain and sensory loss, while dysautonomia usually starts later. Progression of neuropathy may necessitate liver re-transplantation, and subsequent improvement of neuropathy has been reported in some patients. Explant allograft recipients need close monitoring for signs of systemic amyloidosis, neuropathy and dysautonomia as progressive symptoms may require re-transplantation.

"Red-flag" symptom clusters in transthyretin familial amyloid polyneuropathy

Transthyretin familial amyloid polyneuropathy (TTR‐FAP) is a rare, progressive, life‐threatening, hereditary disorder caused by mutations in the transthyretin gene and characterized by extracellular deposition of transthyretin‐derived amyloid fibrils in peripheral and autonomic nerves, heart, and other organs. TTR‐FAP is frequently diagnosed late because the disease is difficult to recognize due to phenotypic heterogeneity. Based on published literature and expert opinion, symptom clusters suggesting TTR‐FAP are reviewed, and practical guidance to facilitate earlier diagnosis is provided. TTR‐FAP should be suspected if progressive peripheral sensory‐motor neuropathy is observed in combination with one or more of the following: family history of a neuropathy, autonomic dysfunction, cardiac hypertrophy, gastrointestinal problems, inexplicable weight loss, carpal tunnel syndrome, renal impairment, or ocular involvement. If TTR‐FAP is suspected, transthyretin genotyping, confirmation of amyloid in tissue biopsy, large‐ and small‐fiber assessment by nerve conduction studies and autonomic system evaluations, and cardiac testing should be performed.

First European consensus for diagnosis, management, and treatment of transthyretin familial amyloid polyneuropathy

Purpose of review

Early and accurate diagnosis of transthyretin familial amyloid polyneuropathy (TTR-FAP) represents one of the major challenges faced by physicians when caring for patients with idiopathic progressive neuropathy. There is little consensus in diagnostic and management approaches across Europe.

Recent findings

The low prevalence of TTR-FAP across Europe and the high variation in both genotype and phenotypic expression of the disease means that recognizing symptoms can be difficult outside of a specialized diagnostic environment. The resulting delay in diagnosis and the possibility of misdiagnosis can misguide clinical decision-making and negatively impact subsequent treatment approaches and outcomes.

Summary

This review summarizes the findings from two meetings of the European Network for TTR-FAP (ATTReuNET). This is an emerging group comprising representatives from 10 European countries with expertise in the diagnosis and management of TTR-FAP, including nine National Reference Centres. The current review presents management strategies and a consensus on the gold standard for diagnosis of TTR-FAP as well as a structured approach to ongoing multidisciplinary care for the patient. Greater communication, not just between members of an individual patient's treatment team, but also between regional and national centres of expertise, is the key to the effective management of TTR-FAP.

Recommendations for presymptomatic genetic testing and management of individuals at risk for hereditary transthyretin amyloidosis

PURPOSE OF REVIEW

These recommendations highlight recent experience in genetic counselling for the severe autosomal-dominant, late-onset transthyretin familial amyloid polyneuropathy (TTR-FAP) disease, and present a structured approach towards identification and monitoring of asymptomatic carriers of the mutated gene.

RECENT FINDINGS

The effectiveness of current treatment options is still limited in patients with TTR-FAP beyond stage I. Diagnosis in the early stages of TTR-FAP is essential to prevent or delay the progression of disease. Existing legal and cultural issues differ among countries within Europe. Experts of the European Network for TTR-FAP (ATTReuNET) concluded that genetic counselling for diagnosed individuals and at-risk family members is mostly beneficial and should be carried out with care by trained professionals. Systematic and regular monitoring of an asymptomatic carrier is necessary to detect early signs of TTR-FAP and maximize the effectiveness of treatment. This includes five areas of assessment: history/clinical examination, sensorimotor function, autonomic dysfunction, cardiac function, and renal function. At least two related symptoms and positive biopsy findings are required to confirm diagnosis of TTR-FAP.

SUMMARY

Early detection of TTR-FAP is essential to improve the prognosis of TTR-FAP. ATTReuNET recommends genetic counselling and routine monitoring for asymptomatic carriers of TTR-FAP.

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.