Rare variant (p.Ser43Asn) of familial transthyretin amyloidosis associated with isolated cardiac phenotype: A case series with literature review

Navigating the penetrance and phenotypic spectrum of inherited cardiomyopathies

Inherited cardiomyopathies are genetic diseases that can lead to heart failure and sudden cardiac death. These conditions tend to run in families, following an autosomal dominant pattern where first-degree relatives have a 50% chance of carrying the pathogenic variant. Despite significant advancements and increased accessibility of genetic testing, accurately predicting the phenotypic expression of these conditions remains challenging due to the inherent variability in their clinical manifestations and the incomplete penetrance observed. This poses challenges in providing patient care and effectively communicating the potential risk of future disease to patients and their families. To address these challenges, this review aims to synthesize the available evidence on penetrance, expressivity, and factors influencing disease expression to improve communication and risk assessment for patients with inherited cardiomyopathies and their family members.

Hereditary transthyretin cardiac amyloidosis proven by endomyocardial biopsy: a single-centre retrospective study and literature review

BACKGROUND

This study aimed to report the genotypes and phenotypes of hereditary transthyretin cardiac amyloidosis (hATTR-CA) in a Western Chinese cohort and review the genetic profiles of this disorder in the Chinese population.

METHODS

Transthyretin (TTR) gene sequencing of probands diagnosed with TTR cardiac amyloidosis and their relatives was performed at West China Hospital of Sichuan University from January 2018 to December 2021. All patients underwent endomyocardial biopsy for light and electron microscopy examinations. Clinical and essential examination materials were retrospectively collected and analysed.

RESULTS

TTR gene alteration was demonstrated in five probands and their two relatives. Three TTR variants were identified, namely, Ser23Asn, Glu54Leu and Thr60Ala. This study is the first to report Glu54Leu as pathogenic mutations in Chinese hATTR-CA patients. The Ser23Asn mutation was the most common mutation in this cohort. Five probands, including two males and three females, were all ethnic Han-Chinese. The median age at diagnosis and delay in diagnosis (interval from onset to diagnosis) was 56 years (range, 54-69 years) and 8 years (range, from 1 to 30 years), respectively. Three cases showed a defined family history of amyloidosis. Endomyocardial biopsies and TTR immunohistochemistry showed positive results in all patients. Two probands died 17.0 months and 21.0 months after diagnosis.

CONCLUSIONS

We identified one novel TTR variants causing hATTR-CA in the West Han Chinese population. To avoid misdiagnosis or delayed diagnosis of hATTR-CA, TTR genotypic screening and endomyocardial biopsy should be performed as soon as possible in cases with heightened clinical suspicion.

Utility of Genetic Testing in Patients with Transthyretin Amyloid Cardiomyopathy: A Brief Review

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly diagnosed condition. Although wild-type transthyretin amyloidosis (ATTRwt) is the most common ATTR-CM, hereditary transthyretin amyloidosis (ATTRv) may also occur. Currently, genetic testing for transthyretin pathogenic variants is recommended for patients with a confirmed clinical diagnosis of ATTR-CM. In fact, confirmation of this autosomal dominant pathogenic variant prompts genetic counselling and allows early identification of affected relatives. Additionally, in the presence of an ATTR-CM-associated polyneuropathy, specific drugs targeting transthyretin can be used. In this paper, we review the utility of genetic testing for the detection of pathogenic variants among patients harboring ATTR-CM and its impact on the natural history of the disease.