Characteristics of South Korean Patients with Hereditary Transthyretin Amyloidosis

Transthyretin mutagenesis: impact on amyloidogenesis and disease

Transthyretin (TTR), a homotetrameric protein found in plasma, cerebrospinal fluid, and the eye, plays a pivotal role in the onset of several amyloid diseases with high morbidity and mortality. Protein aggregation and fibril formation by wild-type TTR and its natural more amyloidogenic variants are hallmarks of ATTRwt and ATTRv amyloidosis, respectively. The formation of soluble amyloid aggregates and the accumulation of insoluble amyloid fibrils and deposits in multiple tissues can lead to organ dysfunction and cell death. The most frequent manifestations of ATTR are polyneuropathies and cardiomyopathies. However, clinical manifestations such as carpal tunnel syndrome, leptomeningeal, and ocular amyloidosis, among several others may also occur. This review provides an up-to-date listing of all single amino-acid mutations in TTR known to date. Of approximately 220 single-point mutations, 93% are considered pathogenic. Aspartic acid is the residue mutated with the highest frequency, whereas tryptophan is highly conserved. "Hot spot" mutation regions are mainly assigned to β-strands B, C, and D. This manuscript also reviews the protein aggregation models that have been proposed for TTR amyloid fibril formation and the transient conformational states that convert native TTR into aggregation-prone molecular species. Finally, it compiles the various in vitro TTR aggregation protocols currently in use for research and drug development purposes. In short, this article reviews and discusses TTR mutagenesis and amyloidogenesis, and their implications in disease onset.

Case Report: A rare transthyretin mutation p.D58Y in a Chinese case of transthyretin amyloid cardiomyopathy

Hereditary transthyretin amyloid (ATTRv) cardiomyopathy (CM) is caused by mutations in the TTR gene. TTR mutations contribute to TTR tetramer destabilization and dissociation, leading to excessive deposition of insoluble amyloid fibrils in the myocardium and finally resulting in cardiac dysfunction. In this article, we report a case of a Chinese patient with transthyretin mutation p.D58Y and provide detailed information on cardiac amyloidosis, including transthoracic echocardiography, cardiac magnetic resonance, and SPECT imaging for the first time. Our report aims to provide a better understanding of ATTR genotypes and phenotypes.

Clinical manifestation, economic burden, and mortality in patients with transthyretin cardiac amyloidosis

Background

Transthyretin cardiac amyloidosis, also known as transthyretin cardiomyopathy (ATTR-CM) is a poorly-recognized disease with delayed diagnosis and poor prognosis. This nationwide population-based study aimed to identify disease manifestations, economic burden, and mortality of patients with ATTR-CM.

Methods

Data of newly diagnosed patients with ATTR-CM between 2013 and 2018 from the Korean National Health Insurance Service were used, covering the entire population. Patient characteristics included comorbidities, medical procedures, and medication. Healthcare resource utilization and medical costs were observed as measures of the economic burden. The Kaplan–Meier survival curve and years of potential life lost (YPLL) from the general population were estimated for disease burden with ATTR CM.

Results

A total of 175 newly diagnosed patients with ATTR-CM were identified. The most common cardiac manifestation was hypertension (51.3%), while the most common non-cardiac manifestation was musculoskeletal disease (68.0%). Mean medical costs at the post-cohort entry date were significantly higher than those at the pre-cohort entry date ($1,864 vs. $400 per patient per month (PPPM), p < 0.001). Of the total medical costs during the study period, the proportion of inpatients cost was 12.9 times higher than the outpatients cost ($1,730 and $134 PPPM, respectively). The median survival time was 3.53 years from the first diagnosis of ATTR-CM, and the mean (SD) YPLL was 13.0 (7.7).

Conclusions

Patients with ATTR-CM had short survival and high medical costs. To reduce the clinical and economic burdens, carefully examining manifestations of disease in patients can help with early diagnosis and treatment.

Clinical recommendations to diagnose and monitor patients with transthyretin amyloid cardiomyopathy in Asia

Transthyretin amyloid cardiomyopathy (ATTR‐CM) is a debilitating and life‐threatening condition with a heterogeneous clinical presentation. Recent guidelines from the United States and Europe have been published to guide clinical practice and to facilitate management conformity by covering current diagnostic and treatment strategies for patients with ATTR‐CM. These guidelines highlight the importance of an early diagnosis to optimize therapeutic outcomes, specifying the use of tests and imaging techniques to allow accurate, noninvasive diagnosis of ATTR‐CM. However, as regional practice variations across Asia may limit access to healthcare, availability of specific tests, and expertise in assessing diagnostic images, there is an ongoing need to provide an Asian perspective on these clinical guidelines. This review article provides practical recommendations for the diagnosis and monitoring of patients with ATTR‐CM in Asia, highlighting the need for additional guidelines to support a broad and diverse population, consider differing healthcare systems and diagnostic testing availability, and provide a flexible yet robust algorithm.

Elderly patients with suspected Charcot-Marie-Tooth disease should be tested for the TTR gene for effective treatments

BACKGROUND AND AIMS

Some hereditary transthyretin (ATTRv) amyloidosis patients are misdiagnosed as Charcot-Marie-Tooth disease (CMT) at onset. We assess the findings to identify ATTRv amyloidosis among patients with suspected CMT to screen transthyretin gene variants for treatments.

METHODS

We assessed clinical, cerebrospinal fluid, and electrophysiological findings by comparing ATTRv amyloidosis patients with suspected CMT (n = 10) and CMT patients (n = 489).

RESULTS

The median (interquartile range) age at onset of neurological symptoms was 69 (64.2-70) years in the ATTRv amyloidosis vs 12 (5-37.2) years in CMT group (Mann-Whitney U, p < 0.01). The proportion of patients with initial sensory symptoms was 70% in the ATTRv amyloidosis group vs 7.1% in CMT group (Fisher's exact, p < 0.01). The proportion of patients with histories of suspected chronic inflammatory demyelinating polyneuropathy (CIDP) were 50% in the ATTRv amyloidosis group vs 8.7% in CMT group (Fisher's exact, p < .01). Other measures and outcomes were not different between the two groups. Five of the six patients with ATTRv amyloidosis received treatment and survived.

INTERPRETATION

For effective treatments, the transthyretin gene should be screened in patients with suspected CMT with old age at onset of neurological symptoms, initial sensory symptoms, and histories of suspected CIDP.

Hereditary transthyretin amyloidosis in mainland China: a unicentric retrospective study

OBJECTIVE

This study aims to report the genotypes and phenotypes of hereditary transthyretin amyloidosis (ATTR) in a large Chinese cohort, yet the clinical and genetic profiles of ATTR remain elusive in mainland China.

METHODS

Fifty-four patients with molecularly confirmed ATTR from 39 unrelated families were identified by sequencing the TTR gene. Sural nerve biopsies were performed in 40 of these cases. The clinical and electrophysiological data were retrospectively collected and analyzed.

RESULTS

The male/female ratio was 42:12. The average age of patients at the onset of the disease was 47.8 ± 13.0 years. The late-onset type occurred in 29 cases (53.7%). Twenty-two probands (56.4%) had a family history with ATTR. The initial symptoms were limb paresthesia in 33 cases (61.1%), autonomic dysfunction in 15 cases (27.8%), and blurred vision in 6 cases (11.1%). A total of 22 different TTR mutations were identified, including Val30Met (25.6%) in 10 families in North China and Ala97Ser in 4 families (10.3%) in South China. Electrophysiological studies revealed general sensorimotor axonal polyneuropathy in 33/44 cases (75.0%), mixed neuropathy with axonal and demyelinating impairment features in 9/44 cases (20.5%) and isolated carpal tunnel syndrome in two cases. Sural nerve biopsies revealed positive Congo red staining in 16/40 cases (40.0%).

CONCLUSION

Chinese patients with ATTR exhibited heterogeneous TTR genotypes and clinical phenotypes. Val30Met remains the most common mutation type in mainland China.

Transthyretin amyloid cardiomyopathy in women: frequency, characteristics, and diagnostic challenges

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive, life-threatening disease characterized by deposition of insoluble amyloid fibrils in the myocardium, resulting in cardiac structural and functional abnormalities and ultimately heart failure. Disease frequency is reportedly lower in women than men, but sex-related differences have not been well established. We conducted a systematic literature review (SLR), based on PRISMA-P guidelines and registered with PROSPERO, to assess whether the epidemiology and clinical presentation of ATTR-CM differ between women and men. MEDLINE, Embase, and Cochrane databases and selected conference proceedings were searched (August 16, 2019) to identify observational and clinical studies reporting sex-specific data for patients with wild-type or hereditary ATTR-CM. Of 193 publications satisfying final eligibility criteria, 69 studies were included in our pooled analysis. Among the 4669 patients with ATTR-CM analyzed, 791 (17%) were women, including 174 (9%), 366 (29%), and 251 (18%) in studies of wild-type, hereditary, and undefined ATTR-CM, respectively. Data available on disease characteristics were limited and very heterogeneous, but trends suggested some cardiac structural/functional differences, i.e., lower interventricular septal and posterior wall thickness and left ventricular (LV) end diastolic diameter, and higher LV ejection fractions, in women versus men across ATTR-CM subtypes. Because LV wall thickness > 12 mm is generally the suggested threshold for ATTR-CM diagnosis in both sexes, smaller cardiac anatomy in women with the disease may lead to underdiagnosis. Additional research and studies are needed to elucidate potential disparities between sexes in ATTR-CM frequency, clinical characteristics, and underlying biological mechanisms. This study was registered within the International Prospective Register of Systematic Reviews (PROSPERO) database of the University of York (CRD42019146995).

Untangling Amyloidosis: Recent Advances in Cardiac Amyloidosis

Cardiac amyloidosis (CA) is a highly underdiagnosed cause of heart failure. Amyloid light-chain (AL) and amyloid transthyretin (ATTR) cardiomyopathy are two major subtypes of cardiac amyloid. Amyloid fibril deposits cause cardiac dysfunction by mechanically infiltrating the myocardium or by direct cardiotoxicity. Achieving a timely diagnosis is important to initiate disease-modifying therapies and improve the survival of patients with CA. Therefore, physicians must be aware of “red flag symptoms” that increase suspicions for CA when assessing heart failure patients. Although endomyocardial biopsy is a definitive diagnostic tool, with recent advances in non-invasive imaging, non-biopsy diagnosis is feasible in ATTR CA. There have been major advances in treatments for both AL and ATTR CA, and survival of CA has improved. In addition to general management of heart failure, numerous treatment options are increasing for both AL and ATTR CA. Given the systemic nature of amyloids, multi-disciplined team approaches are crucial to management of CA. With recent development of diagnosis and treatment options for both AL and ATTR amyloidosis, it is no longer considered a non-treatable disease.