Familial amyloidosis with polyneuropathy associated with TTR Ser50Arg mutation

Hereditary transthyretin amyloidosis: a myriad of factors that influence phenotypic variability

Hereditary transthyretin-related amyloidosis (ATTRv amyloidosis) is a rare and progressively debilitating disease characterized by the deposition of transthyretin (TTR) amyloid fibrils in various organs and tissues, most commonly in the heart and peripheral nerves. This pathological deposition can lead to significant organ dysfunction and, ultimately, organ failure. ATTRv amyloidosis exhibits a broad range of clinical presentations, from purely neurological symptoms to purely cardiac manifestations, as well as mixed phenotypes which result from both neurological and cardiac implications. This wide phenotypical spectrum realistically challenges disease diagnosis and prognosis, especially in individuals without or with an unknown family history. Multiple factors are thought to contribute to this variability, including genetic, epigenetic, and even environmental influences. Understanding these factors is crucial, as they can significantly affect disease expression and progression. This review aims to summarize each of these contributing factors, to help elucidate the current knowledge on the phenotypical variability of ATTRv amyloidosis.

Hereditary Transthyretin Amyloidosis (hATTR) with Polyneuropathy Clusters Are Located in Ancient Mining Districts: A Possible Geochemical Origin of the Disease

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy (FAP)) is an endemic amyloidosis involving the harmful aggregation of proteins, most commonly transthyretin (TTR) but sometimes also apolipoprotein A-1 or gelsolin. hATTR appears to be transmitted as an autosomal dominant trait. Over 100 point mutations have been identified, with the Val30Met substitution being the most common. Yet, the mechanism of pathogenesis and the overall origin of hATTR remain unclear. Here, we argue that hATTR could be related to harmful metal exposure. hATTR incidence is unevenly distributed globally, and the three largest defined clusters exist in Japan, Portugal, and Sweden. All three disease regions are also ancient mining districts with associated metal contamination of the local environment. There are two main mechanisms for how harmful metals, after uptake into tissues and body fluids, could induce hATTR. First, the metals could directly influence the expression, function, and/or aggregation of the proteins involved in hATTR pathology. Such metal-protein interactions might constitute molecular targets for anti-hATTR drug design. Second, metal exposure could induce hATTR -associated genetic mutations, which may have happened several generations ago. These two mechanisms can occur in parallel. In conclusion, the possibility that hATTR could be related to metal exposure in geochemically defined regions deserves further attention.

Impact of Non-Cardiac Clinicopathologic Characteristics on Survival in Transthyretin Amyloid Polyneuropathy

INTRODUCTION

Hereditary (variant) transthyretin amyloidosis (ATTRv) with polyneuropathy (ATTR-PN) is a rare genetic disorder that causes progressive autonomic and sensorimotor neuropathy, severe disability, and death within 10 years of onset. Previous studies have primarily focused on how baseline cardiac characteristics affect mortality, but the impact of non-cardiac baseline characteristics is less defined.

METHODS

We systematically searched PubMed/Medline (1990-2019) to identify studies that assessed the impact of baseline ATTR-PN characteristics on survival. Outcomes were first summarized descriptively. Extracted survival data were then disaggregated, and parametric mixture models were used to assess survival differences among patient groups defined by factors known to affect survival.

RESULTS

The search yielded 1193 records, of which 35 were retained for analysis. Median survival ranged from 0.5 to > 25 years. The largest survival differences were between cohorts who underwent liver transplantation (LTx) versus those who did not. Among LTx cohorts, pre-LTx ATTR-PN disease duration ≥ 7 years, poor nutritional status, and late disease onset reduced median survival by 13, 12, and 10 years, respectively. Other prognostic survival factors included non-Val30Met genotype and baseline presence of urinary incontinence, erectile dysfunction, or muscle weakness.

CONCLUSION

Survival in patients with ATTR-PN is highly variable and affected by non-cardiac baseline characteristics, such as autonomic dysfunction, large fiber involvement, late-onset disease, and non-Val30Met mutation. Careful interpretation of these findings is warranted given that this synthesis did not control for differences between studies. Survival in patients with ATTR-PN remains poor among those who are untreated or with delayed diagnosis.

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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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.

Amyloid Polyneuropathy and Myocardial Amyloidosis 10 Years after Domino Liver Transplantation from a Patient with a Transthyretin Ser50Arg Mutation

A 54-year-old man with polycystic liver disease received a domino liver transplantation (DLT) from a patient of hereditary ATTR amyloidosis with the transthyretin Ser50Arg mutation. Ten years after transplantation, he felt a slight numbness in his toes, and cardiac amyloidosis was simultaneously suspected upon a heart function evaluation. Biopsy specimens from the myocardium revealed transthyretin amyloidosis with the Ser50Arg mutation. Oral tafamidis therapy has inhibited the progression of neurological and cardiovascular symptoms this far. We herein report this first case of amyloid polyneuropathy and myocardial amyloidosis after DLT from hereditary ATTR amyloidosis with a transthyretin Ser50Arg mutation and discuss similar cases of other mutations.

Gender differences in the clinical course of Finnish gelsolin amyloidosis

PURPOSE

To investigate gender differences in Finnish gelsolin amyloidosis (AGel amyloidosis).

PATIENTS AND METHODS

AGel amyloidosis patients, who were members of Finnish Amyloidosis Association (SAMY), filled in a questionnaire compiling known and suspected aspects of their disease. Telephone interviews and hospital medical records, when available, complemented the questionnaire. The data were entered to the database in order to create a national AGel amyloidosis patient registry (FIN-GAR).

RESULTS

A total of 227 patients, 156 women and 71 men, participated in the study. The women in our registry noticed their first symptoms at the median age of 39 years versus 43 years for men (p = 0.01). At the age in which the diagnosis was made there was a trend to be observed between men and women (women: 39 years versus men: 43 years, p = 0.053). Corneal lattice dystrophy was diagnosed in significantly younger women than men (median ages 41 versus 49 years, respectively, p = 0.01). Of other ophthalmological manifestations, corneal ulcer, impaired vision and glaucoma were all diagnosed at least 5 years earlier in women, although differences were not statistically significant. Ophthalmological manifestations, such as dry eyes and corneal ulcer; dermatological signs, such as blepharochalasis, and also neurological symptoms, such as myokymia and carpal tunnel syndrome, were more prevalent among women.

CONCLUSIONS

In the largest so far available study on AGel amyloidosis we show that women developed symptoms and signs of AGel amyloidosis at younger age. Especially eye-related problems occurred earlier and together with nerve and skin manifestations, the characteristic clinical triad in AGel amyloidosis, were more common in women. However, a clear limitation of our study was a selection bias caused by a significant underrepresentation of men in the study population.

Ophthalmological manifestations in hereditary transthyretin (ATTR V30M) carriers: a review of 513 cases

PURPOSE

Assessment of ocular involvement in transthyretin-related familial amyloidosis with polyneuropathy (FAP) in a large cohort of Portuguese patients.

METHODS

We reviewed the medical records of 513 Portuguese FAP mutation carriers, at the Ophthalmology Service, Centro Hospitalar do Porto, between 1 January 2008 and 31 January 2013. Abnormal conjunctiva vessels (ACV), Schirmer test, tear break-up time (TBUT), amyloid deposition on the iris (DAI), scalloped iris, amyloid deposition on the anterior capsule of the lens (DAL), vitreous amyloidosis, retinal amyloid angiopathy and glaucoma were evaluated and registered.

RESULTS

Of the 513 carriers, 477 (93%) had clinical systemic disease with a median duration of 9.3 (5.1-13.7) years and 247 were men. Of these, 343 (72%) had been liver transplanted, on median of 6.6 (3.3-10.8) years before inclusion in this study. No ocular abnormalities were identified in the asymptomatic carriers (7%). The abnormalities observed with decreasing frequency were abnormal TBUT (379 patients, 79.5%, 751 eyes), abnormal Schirmer test (320 patients, 67%, 635 eyes), DAI (183 patients, 38.4%, 350 eyes), DAL (157 patients, 32.9%, 308 eyes), scalloped iris (133 patients, 27.9%, 238 eyes), glaucoma (97 patients, 20%, 165 eyes), vitreous amyloidosis (83 patients, 17.4%, 139 eyes), ACV (68 patients, 14%, 136 eyes) and amyloidotic retinal angiopathy (21 patients, 4%, 32 eyes). Patients with abnormal Schirmer test (p < 0.001), scalloped iris (p = 0.006) and vitreous amyloidosis (p = 0.007) were significantly older than the others. According to their age of onset of systemic disease, the patients have been split into early-onset (<40 years old), intermediate-onset (40-50 years old), late onset (>50 years old) and asymptomatic carriers. We observed a statistically significant difference in the prevalence of ACV (p = 0.045) and of an abnormal Schirmer test (p = 0.004) between groups. Transplanted patients have a significantly higher prevalence of DAI (p = 0.001), DAL (p = 0.009) and vitreous amyloidosis (p = 0.025) than non-transplanted patients. Of the 165 eyes with glaucoma, 92.1% had scalloped iris (p < 0.001) and of 32 eyes with retinal amyloidotic angiopathy, 68.8% had vitreous amyloidosis (p < 0.001). All prevalences increased with time of disease. The earliest ocular manifestations were abnormal Schirmer test and abnormal TBUT (12% and 17% at 5 years of clinical disease) and the least prevalent was retinal amyloid angiopathy (8% at 15 years of clinical disease).

CONCLUSION

Ocular disorders in FAP patients are common, and their prevalence increases with disease duration. Prevalence is influenced by several factors, such as the age at onset of FAP and liver transplantation.

FAP neuropathy and emerging treatments

Transthyretin familial amyloid polyneuropathy (TTR-FAP) classically presents as a length dependent small fiber polyneuropathy in endemic countries like Portugal. In nonendemic countries, it may mimic a variety of chronic polyneuropathies, with several phenotypes: ataxic, upper limb onset neuropathy, or motor. In these cases, there is usually a late onset and no positive family history. TTR gene sequencing appears the most pertinent first-line test for diagnosis. Cardiac involvement of various severities is common in FAP. Liver transplantation remains the standard antiamyloid therapy with better results in Val30Met TTR-FAP of early onset. Antiamyloid medication has been developed. (1) TTR stabilizers: Tafamidis was the first drug approved in Europe in stage 1 (walking unaided) TTR-FAP to slow progression of the disease; diflunisal has been assessed in a phase 3 clinical trial; (2) TTR gene silencing is a new strategy to inhibit production of both mutant and nonmutant TTR with antisense oligonucleotides or SiRNA (2 ongoing phase 3 clinical trials).

Description of transthyretin S50A, S52P and G47A mutations in familial amyloidosis polyneuropathy

OBJECTIVE

To describe 58 subjects with rare TTR mutations, and to compare the different biomarkers between carriers and patients.

METHODS

TTR gene sequence test was performed in 15 suspicious subjects and in their direct family. All positive subjects undertook prospective evaluations in a period of 49 months.

RESULTS

Of 95 genetic tests performed, 58 (61%) were positive for TTR mutations, Ser50Arg mutation in 38 (65%), Ser52Pro in 15 (26%) and Gly47Ala in 5 (9%). Initial symptoms were neuropathic in 19 (73%), gastrointestinal in 6 (23%) and autonomic in 1 (4%).

CONCLUSIONS

The natural history of Ser50Arg, Ser52Pro and Gly47Ala TTR mutations is similar to the Val30Met mutation described in endemic areas. The small fiber assessments were the initial tests to show abnormalities in asymptomatic subjects.