Transthyretin-related hereditary amyloidosis with recurrent vomiting and renal insufficiency as the initial presentation: A case report

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.

Hypertrophic cardiomyopathy caused by a heterozygous variant in TTR gene: A case report

RATIONALE

We report a rare case of hypertrophic cardiomyopathy (HCM) caused by a heterozygous variant in TTR gene.

PATIENT CONCERNS

The proband had been vomiting without obvious inducement since the age of 27, accompanied by the expulsion of stomach contents. At the age of 28, she began to suddenly syncope.

DIAGNOSIS

Cardiac magnetic resonance showed thickening of the right ventricular lateral wall and ventricular septum. The left ventricular diastolic function was limited. Targeted Sanger sequencing validates the presence of mutation p.Leu75Pro in TTR gene.

INTERVENTIONS AND OUTCOMES

After admission to hospital for syncope, she was given metoprolol tablets 25 mg bid, spironolactone tablets 20 mg qd, and trimetazidine 20 mg tid. Her symptoms improved after taking the medicine.

LESSONS

The results of this case show that HCM caused by TTR mutation is not easy to be identified and treatment is easy to be delayed. Therefore, high-risk patients with amyloidosis should be evaluated as soon as possible. Timely diagnosis of HCM caused by TTR mutation before irreversible organ damage is essential for proper treatment and better outcomes.

Clinical phenotypes and genetic features of hereditary transthyretin amyloidosis patients in China

Background

Hereditary transthyretin amyloidosis (hATTR) is a progressive and fatal disease with heterogenous clinical presentations, limited diagnosis and poor prognosis. This retrospective analysis study aimed to report the genotypes and phenotypes of herediary transthyretin amyloidosis (hATTR) in Chinese through a systematic review of published literature.

Methods

The systematic review included structured searches of peer-reviewed literature published from 2007 to 2020 of following online reference databases: PubMed, Web of Science and the literature database in China. Extracted data included sample size, personal information (sex, age, natural course, family history), mutation type, clinical milestones and reason of death.

Results

We described 126 Chinese patients with hereditary transthyretin amyloidosis identified through a systematic review of 30 studies. The most common genotype in the Chinese population was Gly83Arg (25, 19.8%), which most likely presented visual and neurological abnormalities without reported death. The second and third most common genotypes were Val30Met (20, 15.9%) and Val30Ala (10, 7.9%). Peripheral neurological manifestations (91, 72%) were dominant in 126 patients. The followed manifestation was autonomic neurological abnormalities (73, 58%). Half of the cases were reported to have visual disorders, and nearly one-third of the cases presented cardiac abnormalities. Among all 126 reported patients, 46.03% were classified as neurological type, 30.16% as mixed type and only 2.38% as cardiac type. In addition. Chinese patients were mostly early onset, with age of onset at 41.8 (SD: 8.9) years, and the median time from onset to death was 7.5 [IQR: 5.3] years. Patients with cardiac involvement had a shorter survival duration (log Rank (Mantel-Cox), χ² = 26.885, P < 0.001).

Conclusions

This study focused on 126 Chinese hATTR patients obtained from a literature review. A total of 26 kinds of TTR mutations were found and the most common one was Gly83Arg. As for phenotype, 46.03% were classified as neurological type, 30.16% as mixed type and only 2.38% as cardiac type. Chinese hATTR patients were mostly early onset (AO 41.8 years), and the median time from onset to death was 7.5 years.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02481-9.

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.

Update on the clinical utility of an RNA interference-based treatment: focus on Patisiran

RNA interference (RNAi) is a naturally existing endogenous mechanism for post-transcriptional gene regulation, nowadays commonly utilized for functional characterization of genes and development of potential treatment strategies for diseases. RNAi-based studies for therapy, after being examined for over a decade, are finally in the pipeline for developing a potential treatment for the mutated transthyretin (TTR) gene, which gives rise to a dysfunctional TTR protein. This dysfunctional protein causes TTR amyloidosis (ATTR), an inherited, progressively incapacitating, and often fatal genetic disorder. TTR is a protein produced in the liver, and functions as a carrier for retinol-binding protein and also thyroxine. This protein facilitates the transport of vitamin A around the human body. A mutation or misprint in the code of this protein results in an abnormal folding of the protein. Therefore, not only does the transportation of the vitamin A become disabled, but also there will be formation of clusters called amyloid deposits, which attack the heart and the nerves causing some patients to be unconditionally bound to bed. ATTR is a hereditary autosomal dominant disease with a 50% chance of inheritance by offspring, even with just one of the parents having a single defective allele of this gene. Alnylam Pharmaceuticals worked on the concept of RNAi therapy for years, which led to the introduction of lipid nanoparticles encircling small interfering RNAs. The drug showed extremely positive results since the first trial, and a great percentage of defective protein reduction. This drug was later named Patisiran.