Effects of liver transplantation and tafamidis in hereditary transthyretin amyloidosis caused by transthyretin Leu55Pro mutation: a case report

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.

Pharmacological Chaperones and Protein Conformational Diseases: Approaches of Computational Structural Biology

Whenever a protein fails to fold into its native structure, a profound detrimental effect is likely to occur, and a disease is often developed. Protein conformational disorders arise when proteins adopt abnormal conformations due to a pathological gene variant that turns into gain/loss of function or improper localization/degradation. Pharmacological chaperones are small molecules restoring the correct folding of a protein suitable for treating conformational diseases. Small molecules like these bind poorly folded proteins similarly to physiological chaperones, bridging non-covalent interactions (hydrogen bonds, electrostatic interactions, and van der Waals contacts) loosened or lost due to mutations. Pharmacological chaperone development involves, among other things, structural biology investigation of the target protein and its misfolding and refolding. Such research can take advantage of computational methods at many stages. Here, we present an up-to-date review of the computational structural biology tools and approaches regarding protein stability evaluation, binding pocket discovery and druggability, drug repurposing, and virtual ligand screening. The tools are presented as organized in an ideal workflow oriented at pharmacological chaperones' rational design, also with the treatment of rare diseases in mind.

Deterioration after Liver Transplantation and Transthyretin Stabilizer Administration in a Patient with ATTRv Amyloidosis with a Leu58Arg (p.Leu78Arg) TTR Variant

We herein report a 44-year-old Japanese man with hereditary transthyretin amyloidosis (ATTRv amyloidosis) harboring the variant Leu58Arg (p.Leu78Arg) in TTR in whom we conducted an observational study with liver transplantation (LT) and transthyretin (TTR) stabilizers (tafamidis and diflunisal) for 9 years. This patient showed gradual deterioration of sensory, motor, and autonomic neuropathy symptoms after LT. Furthermore, cardiac amyloidosis gradually developed. Although the present case showed deterioration of the symptoms after disease-modifying treatments, LT might be suitable in patients with the same variant if they are young and in good condition due to a long survival after LT.

Targeted Therapies for Hereditary Peripheral Neuropathies: Systematic Review and Steps Towards a 'treatabolome'

Background:

Hereditary peripheral neuropathies are inherited disorders affecting the peripheral nervous system, including Charcot-Marie-Tooth disease, familial amyloid polyneuropathy and hereditary sensory and motor neuropathies. While the molecular basis of hereditary peripheral neuropathies has been extensively researched, interventional trials of pharmacological therapies are lacking.

Objective:

We collated evidence for the effectiveness of pharmacological and gene-based treatments for hereditary peripheral neuropathies.

Methods:

We searched several databases for randomised controlled trials (RCT), observational studies and case reports of therapies in hereditary peripheral neuropathies. Two investigators extracted and analysed the data independently, assessing study quality using the Oxford Centre for Evidence Based Medicine 2011 Levels of Evidence in conjunction with the Jadad scale.

Results:

Of the 2046 studies initially identified, 119 trials met our inclusion criteria, of which only 34 were carried over into our final analysis. Ascorbic acid was shown to have no therapeutic benefit in CMT1A, while a combination of baclofen, naltrexone and sorbitol (PXT3003) demonstrated some efficacy, but phase III data are incomplete. In TTR-related amyloid polyneuropathy tafamidis, patisiran, inotersen and revusiran showed significant benefit in high quality RCTs. Smaller studies showed the efficacy of L-serine for SPTLC1-related hereditary sensory neuropathy, riboflavin for Brown-Vialetto-Van Laere syndrome (SLC52A2/3) and phytanic acid-poor diet in Refsum disease (PHYH).

Conclusions:

The ‘treatable’ variants highlighted in this project will be flagged in the treatabolome database to alert clinicians at the time of the diagnosis and enable timely treatment of patients with hereditary peripheral neuropathies.

Canadian Guidelines for Hereditary Transthyretin Amyloidosis Polyneuropathy Management

Hereditary transthyretin-mediated (hATTR) amyloidosis is a progressive disease caused by mutations in the TTR gene leading to multisystem organ dysfunction. Pathogenic TTR aggregation, misfolding, and fibrillization lead to deposition of amyloid in multiple body organs and frequently involve the peripheral nerve system and the heart. Common neurologic manifestations include: sensorimotor polyneuropathy (PN), autonomic neuropathy, small-fiber PN, and carpal tunnel syndrome. Many patients have significant progression due to diagnostic delays as hATTR PN is not considered within the differential diagnosis. Recently, two effective novel disease-modifying therapies, inotersen and patisiran, were approved by Health Canada for the treatment of hATTR PN. Early diagnosis is crucial for the timely introduction of these disease-modifying treatments that reduce impairments, improve quality of life, and extend survival. In this guideline, we aim to improve awareness and outcomes of hATTR PN by making recommendations directed to the diagnosis, monitoring, and treatment in Canada.

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

RATIONALE

Hereditary amyloidosis is diagnosed worldwidely with an increasing incidence. As the most common form, transthyretin-related hereditary amyloidosis (ATTR amyloidosis) is an autosomal dominant inherited disease due to mutations of TTR. Over the past several decades, more than 130 mutations have been reported. Previous studies suggested that ATTR amyloidosis initially showed polyneuropathy and autonomic dysfunction but later involving many visceral organs, such as kidney.

PATIENT CONCERNS

A young proband carrying TTR p.Leu75Pro mutation, a reported aggressive variant, initially presenting repeat vomiting and impaired renal function was described in a Chinese family.

DIAGNOSES

ATTR amyloidosis patient was diagnosed by renal biopsy and gene sequencing.

INTERVENTIONS

Allograft liver transplantation (LT).

OUTCOMES

Symptom relief but serum creatinine increased.

LESSONS SUBSECTIONS

This case illustrated the clinical and pathologic phenotype of an ATTR amyloidosis patient who initially presented impaired renal function and p.Leu75Pro variant was found by sequencing the coding region of TTR gene. Kidney is one of the most common and vulnerable organs of amyloidosis, and renal function should be closely monitored.

Small molecules as therapeutic agents for inborn errors of metabolism

Most inborn errors of metabolism (IEM) remain without effective treatment mainly due to the incapacity of conventional therapeutic approaches to target the neurological symptomatology and to ameliorate the multisystemic involvement frequently observed in these patients. However, in recent years, the therapeutic use of small molecules has emerged as a promising approach for treating this heterogeneous group of disorders. In this review, we focus on the use of therapeutically active small molecules to treat IEM, including readthrough agents, pharmacological chaperones, proteostasis regulators, substrate inhibitors, and autophagy inducers. The small molecules reviewed herein act at different cellular levels, and this knowledge provides new tools to set up innovative treatment approaches for particular IEM. We review the molecular mechanism underlying therapeutic properties of small molecules, methodologies used to screen for these compounds, and their applicability in preclinical and clinical practice.