A new transthyretin variant (Ser23Asn) associated with familial amyloidosis in a Portuguese patient

Clinical Profile and Prognosis of Hereditary Transthyretin Amyloid Cardiomyopathy: A Single-Center Study in South China

Background

Hereditary transthyretin amyloid cardiomyopathy (ATTR-CM) is a genotypically heterogeneous disorder with a poor prognosis. There is limited literature describing the variants responsible for ATTRv in areas outside the United State, the United Kingdom and Europe. This study was performed to describe the clinical characteristics and genotypic profiles of this disease in South China.

Methods

This was a single-center retrospective study that evaluated 29 patients with a confirmed diagnosis of hereditary transthyretin amyloid cardiomyopathy enrolled from January 2016 to November 2021.

Results

93.1% patients were male and the median age of symptom onset was 53 (46, 62.5) years old. The initial manifestations of ATTR-CM were cardiovascular symptoms (55.2%), neuropathy (41.4%) and vitreous opacity (3.4%). Phenotypes at diagnosis were mixed (82.8%), predominant cardiac (6.9%), neurological (6.9%) and ophthalmic (3.4%). Poor R-wave progression (41%), pseudo-infarct (31%) and low-voltage (31%) patterns were common findings on electrocardiogram. Unexplained increased wall thickness was observed in all 29 patients, with mean septal and posterior wall thicknesses of 14.25 ± 6.26 mm and 15.34 ± 2.84 mm, respectively. Diastolic dysfunction was also seen in all 29 patients, and 17 (58%) had a restrictive fill pattern at diagnosis. Nine different missense mutations of the TTR gene were found in 29 patients from 23 families, with c.349G>T (p.Ala117Ser) the most common mutation. The median survival time after diagnosis was 47.6 (95% CI 37.9-57.4) months, with 1, 3 and 5-year survival rates of 91.2%, 74% and 38% respectively. Patients with advanced heart failure (National Amyloidosis Staging stage II/III) had worse survival than stage I [Breslow (Generalized Wilcoxon), χ2 = 4.693, P = 0.03)].

Conclusions

ATTR amyloidosis genotypes and phenotypes are highly heterogeneous. Advanced heart failure predicts a poor prognosis. Understanding the different clinical profiles of ATTR cardiac amyloidosis with different genotype is important to its early recognition.

Ocular Involvement in Hereditary Amyloidosis

The term amyloidosis describes a group of rare diseases caused by protein conformation abnormalities resulting in extracellular deposition and accumulation of insoluble fibrillar aggregates. So far, 36 amyloid precursor proteins have been identified, and each one is responsible for a specific disease entity. Transthyretin amyloidosis (ATTRv) is one of the most common forms of systemic and ocular amyloidosis, due to the deposition of transthyretin (TTR), which is a transport protein mainly synthesized in the liver but also in the retinal pigment epithelial cells. ATTRv amyloidosis may be misdiagnosed with several other conditions, resulting in a significant diagnostic delay. Gelsolin and keratoepithelin are other proteins that, when mutated, are responsible for a systemic amyloid disease with significant ocular manifestations that not infrequently appear before systemic involvement. The main signs of ocular amyloid deposition are in the cornea, irido-corneal angle and vitreous, causing complications related to vasculopathy and neuropathy at the local level. This review aims at describing the main biochemical, histopathological and clinical features of systemic amyloidosis associated with eye involvement, with particular emphasis on the inherited forms. We discuss currently available treatments, focusing on ocular involvement and specific ophthalmologic management and highlighting the importance of a prompt treatment for the potential sight-threatening complications derived from amyloid deposition in ocular tissues.

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

Background

p.Ser43Asn is a very rare transthyretin (TTR) mutation leading to familial amyloidosis of transthyretin type, ATTR amyloidosis. It was previously observed in four patients worldwide and is associated almost invariably with an isolated cardiac phenotype.

Methods and Results

We report here on an Italian family with early‐onset cardiomyopathy and aggressive disease course in the affected individuals leading untreated to cardiac death before 55 years of age. We describe the clinical phenotype and imaging findings of two affected siblings, who were treated with tafamidis at an early disease stage, and their affected mother, who died 9 years ago due to refractory heart failure. The review of the available literature highlights the fact that until recently ATTR amyloidosis may have been misdiagnosed as other types of hypertrophic cardiomyopathy.

Conclusion

A better characterization of the genotype–phenotype associations is crucial to achieve optimal outcomes and facilitate informed decisions when treating individuals with rare mutations.

Amyloidosis and Ocular Involvement: an Overview

Purpose: To describe the ophthalmic manifestations of amyloidosis and the corresponding therapeutic measures.Methods: The 178 patients included in the study had different types of amyloidosis, diagnosed at a single internal medicine institution (Bari, Italy). To provide a comprehensive review of the types of amyloidosis that can be associated with ocular involvement, the images and clinical descriptions of patients with amyloidosis structurally related to gelsolin, keratoepithelin and lactoferrin were obtained in collaborations with the ophthalmology departments of hospitals in Mainz (Germany) and Helsinki (Finland).Results: Overall, ocular morbidity was detected in 41 of the 178 patients with amyloidosis (23%). AL amyloidosis was diagnosed in 18 patients with systemic disease, 3 with multiple myeloma, and 11 with localized amyloidosis. AA amyloidosis was detected in 2 patients with rheumatoid arthritis and 3 with Behçet syndrome, and transthyretin amyloidosis in 4 patients. The treatment of AL amyloidosis is based on chemotherapy to suppress the production of amyloidogenic L-chains and on surgical excision of orbital or conjunctival masses. AA amyloidosis is managed by targeting the underlying condition. Vitreous opacities and additional findings of ocular involvement in patients with transthyretin amyloidosis indicate the need for pars plana vitrectomy. Gelsolin amyloidosis, characterized by lattice corneal amyloidosis and polyneuropathy, results in recurrent keratitis and corneal scarring, such that keratoplasty is inevitable. In patients with lattice corneal dystrophies associated with amyloid deposits of keratoepithelin fragments, corneal transparency is compromised by deposits of congophilic material in the subepithelial layer and deep corneal stroma. Patients with established corneal opacities are treated by corneal transplantation, but the prognosis is poor because recurrent corneal deposits are possible after surgery. In patients with gelatinous drop-like dystrophy, the amyloid fibrils that accumulate beneath the corneal epithelium consist of lactoferrin and can severely impair visual acuity. Keratoplasty and its variants are performed for visual rehabilitation.Conclusion: A routine ophthalmic follow-up is recommended for all patients with established or suspected amyloidosis, independent of the biochemical type of the amyloid. Close collaboration between the ophthalmologist and the internist will facilitate a more precise diagnosis of ocular involvement in amyloidosis and allow the multidisciplinary management of these patients.Abbreviations: CD: corneal dystrophy; CLA: corneal lattice amyloidosis; CNS: central nervous system; CT: computed tomography; FAP: familial amyloidotic polyneuropathy; GDLCD: gelatinous drop-like corneal dystrophy; GLN: gelsolin; LCD: lattice corneal dystrophy; MRI: magnetic resonance imaging; OLT: orthotopic liver transplantation; TEM: transmission electron microscopy; TGFBI: transforming growth factor β induced; TTR: transthyretin.

Rapidly Progressive Transthyretin-Mediated Amyloidosis in a Domino Liver Transplant Recipient of a Ser23Asn Donor

Domino liver transplantation, in which the liver of a patient with transthyretin-mediated amyloidosis is transplanted into another patient, has been an established procedure performed at several centers across the world. The risk of developing systemic amyloidosis in transthyretin-mediated amyloidosis liver transplant recipients is a topic of ongoing investigation. We report a case of rapidly progressive transthyretin amyloidosis in a patient who received a liver from a donor with a rare Ser23Asn mutation. We advise exercising caution when considering domino liver transplantation in patients with this particular mutation.

Technetium pyrophosphate myocardial uptake and peripheral neuropathy in a rare variant of familial transthyretin (TTR) amyloidosis (Ser23Asn): a case report and literature review

We report the fourth case of transthyretin amyloidosis (ATTR) Ser23Asn in a 41-year-old Ecuadorian male. He has a pedigree that spans seven generations and involves 24 family members who suffered early cardiac death. Salient presenting symptoms were fatigue, shortness of breath, and peripheral neuropathy. The diagnosis of cardiac amyloid was confirmed by immunohistochemical staining of an endomyocardial biopsy, genotyping and by technetium pyrophosphate ((99m)Tc-PYP) scintigraphy, which remains to be established as a reliable tool to visualize myocardial amyloid involvement in patients with the Ser23Asn transthyretin (TTR) variant. The patient underwent successful combined heart and liver transplant. We add to the current ATTR literature that in patients with the rare Ser23Asn mutation, peripheral nerve in addition to cardiac involvement can occur and (99m)Tc-PYP scintigraphy can be used as an imaging modality to visualize myocardial amyloid.

Restrictive cardiomyopathy in inherited ATTR amyloidosis (TTR-Ser23Asn) in a patient of German-Italian extraction

Amyloidosis occurs when certain soluble proteins are transformed into amyloid fibrils in the extracellular space. Most common are the light-chain amyloidoses; less common is the AA-amyloidosis, which follows chronic inflammatory diseases, and the amyloidoses of transthyretin (TTR) origin. We report on a women of Italian-German origin with the mutation TTR (Ser23Asn). Whole body scintigraphy using TC99m-DPD showed end stage hereditary amyloidosis caused by ATTR with predominant tracer retention in the myocardium. Myocardial biopsies revealed the presence of amyloid by Congo red staining. Further immunohistochemical analysis showed ATTR amyloidosis. DNA sequencing revealed a point mutation of the transthyretin gene leading to a single amino acid substitution. The only effective treatment in patients with manifest cardiac ATTR amyloidosis is combined heart and liver transplantation. Our patient was placed on a list for this procedure, but unfortunately she died during the standby procedure due to urosepsis.

Detailed structural analysis of amyloidogenic wild-type transthyretin using a novel purification strategy and mass spectrometry

Wild-type transthyretin (TTR), normally a soluble plasma-circulating protein, can be amyloidogenic, i.e., form tissue-deposited fibrillar material in the extracellular matrix of various organs throughout the body. Senile systemic amyloidosis (SSA) is one such pathology and features TTR-containing amyloid deposits that are found primarily in the heart. The cause for this transition from soluble to insoluble protein in SSA is yet to be determined as specific structural features that might favor TTR fibrillogenesis have not yet been identified. The precise characterization of ex vivo fibril deposits might provide insight, but structural analyses of TTR from amyloid deposits have been hindered thus far by the lack of purification strategies that overcome the insolubility of the tissue-derived protein without degrading it. Consequently, the true biochemical nature of deposited TTR remains in question. In this study, we provide detailed analyses of both the soluble (serum) and deposited (tissue) forms of TTR from cases of SSA. In the serum, a distribution of mixed disulfides, specifically S-sulfonated and S-cysteinylated forms of TTR, as well as the unmodified protein were identified. The relative levels of the three TTR species in the SSA group were comparable to amounts present in sera from age-matched control groups. For characterization of the amyloid deposited TTR, we investigated cardiac tissue samples obtained from three separate cases of SSA. We report a novel chromatographic purification strategy performed under nonreducing conditions (to maintain cysteine disulfide status) and the use of this procedure in conjunction with detailed mass spectrometric analysis of TTR from the amyloid deposits. A series of C-terminal TTR fragments with N-termini ranging from amino acids 46 to 55 were identified. We also determined that the deposits in all samples contained Cys10 disulfide-linkedhomodimers composed of full-length TTR monomers. This last finding suggests an important role for Cys10 conjugation in the transition from soluble TTR to the pathological amyloid fibril.

Expression, purification, and in vitro cysteine-10 modification of native sequence recombinant human transthyretin

Transthyretin (TTR) is a serum protein that is also a prominent component of deposits in two different types of systemic amyloid disease, senile systemic and familial TTR amyloidoses. Studies of recombinant TTR (rTTR) have provided many insights into the relationship between protein structure and amyloidogenicity. Yet, there is no existing recombinant system that results in high yield production of a protein that is identical in primary structure to human TTR. To date, most published studies have generated rTTR using the human gene sequence, which is poorly expressed in Escherichia coli. In addition, the gene sequence has been flanked by a 3' AUG start codon to initiate translation, resulting in the expression of a protein containing an N-terminal methionine residue not present in the human protein. We present an improved technique which can be used to generate large quantities of human native sequence TTR. Our recombinant system utilizes a gene containing codons altered for efficient expression in E. coli and an N-terminal polyhistidine tag for simplified purification. Optimization of this system was accomplished by generating a modified polyhistidine tag that was efficiently removed by dipeptidyl aminopeptidase I (DAPase). This is the first report detailing an effective and useful method for producing rTTR containing an amino acid sequence identical to human TTR. Furthermore, we describe the thiol modification of the recombinant protein to achieve exact replication of the several prominent post-translationally modified forms of TTR that have been identified in human serum.

Clinical and pathological studies of cardiac amyloidosis in transthyretin type familial amyloid polyneuropathy

To clarify the clinicopathological features of cardiac amyloidosis in transthyretin (TTR) familial amyloid polyneuropathy (FAP), 169 patients were divided into three groups. Group I consisted of 113 patients with ATTR Val30Met who originated from an endemic focus, II consisted of 36 patients with ATTR Val30Met in nonendemic areas, and III consisted of 20 patients who had non-Val30Met ATTRs with 15 different gene mutations. The median age of onset in Group I was 34 years. On our initial examination, only one 65-year-old female patient was found to be suffering from congestive heart failure. During the follow-up of 65 patients, 7 developed congestive heart failure, the average duration of their illness being 8.7 years. In Group II, the median age of onset was 53 years and 6 of the 36 patients were diagnosed as having cardiac amyloidosis in the course of this disease. In 20 autopsied patients with ATTR Val30Met, congestive heart failure was clinically seen in 6 of the 20 and all 6 showed considerably increased cardiac weight (500g or more). In Group III patients with non-Val30Met ATTRs, the median age of onset was 51.5 years and 14 of the 20 patients had cardiac amyloidosis with congestive heart failure on admission or soon after a definite diagnosis. Cardiac amyloidosis occurs in the classical form of FAP with ATTR Val30Met, especially in older patients, and is also a common clinical manifestation in FAP patients with non-Val30Met ATTRs. In the pathogenesis of cardiac amyloidosis in ATTR FAP, aging seems to play an important role.

Review: small-fiber neuropathy

BACKGROUND

Most peripheral neuropathies involve large as well as small-fiber dysfunction. A small subset of neuropathies present with restricted or predominant small-fiber involvement.

REVIEW SUMMARY

In this review, we discuss the differential diagnosis, clinical presentation, evaluation, and treatment of small-fiber neuropathies. Although these neuropathies are rare, their differential diagnosis is broad, and includes many disorders, including metabolic, toxic, inflammatory, infectious, and genetic etiologies. As small fibers subserve pain and autonomic functions, these neuropathies usually present with pain and temperature loss, painful dysesthesias, autonomic dysfunction, or a combination. These neuropathies are especially challenging as nerve conductions and EMG, which help guide the evaluation of most peripheral neuropathies, may have normal findings in patients with small-fiber neuropathies. Other specialized studies, including tests of autonomic function, intraepidermal nerve fiber analysis, and quantitative sensory testing, are often required to confirm the presence of a small-fiber neuropathy. In some cases, the underlying etiology can be directly treated. In most, management is limited to symptomatic treatment of sensory and autonomic dysfunction.

CONCLUSION

Small-fiber neuropathies are a heterogeneous group of disorders. They vary in etiologies and require special attention, as many disorders are rare and the differential diagnosis is broad. Evaluation is often extensive and may need pathologic specimen. Many patients respond to symptomatic therapy, but some are difficult to treat.

Transthyretin mutations in hyperthyroxinemia and amyloid diseases

Over 80 different disease-causing mutations in transthyretin (TTR) have been reported. The vast majority are inherited in an autosomal dominant manner and are related to amyloid deposition, affecting predominantly peripheral nerve and/or the heart. A small portion of TTR mutations are apparently non-amyloidogenic. Among these are mutations responsible for hyperthyroxinemia, presenting high affinity for thyroxine (a TTR ligand). Compound heterozygotic individuals for TTR mutants have been described; noteworthy is the clinically protective effect exerted by a non-pathogenic over a pathogenic mutation. Current TTR mutations and their significance are briefly reviewed here.

Postmortem findings in two familial amyloidosis patients with transthyretin variant Asp38Ala

Postmortem findings in 2 familial amyloidosis patients with the transthyretin variant (ATTR), Asp38Ala, are described Both showed cardiac failure, and progressive peripheral and autonomic neuropathy and died at the ages 82 and 57, respectively. TTR immunoreactive amyloid deposition was observed to be extensive in the myocardium, peripheral nerves, sympathetic ganglia and gastrointestinal tract. The pulmonary parenchyma was also diffusely involved, but renal glomeruli, follicular tissues of the thyroid, and the leptomeninges and subarachnoidal vessels of the central nervous system showed little deposition. The latter findings are not usually seen in the patients with ATTR Val30Met, the most common form of familial amyloidosis. Additionally, the clinicopathological findings of familial amyloidosis with ATTR Asp38Ala seem to vary in the different individuals.

Application of multishot acquisition in Fourier transform mass spectrometry

A new method of ion injection and trapping is discussed wherein ions are accumulated over several laser shots in the FT-ICR cell prior to detection. This allows accumulation of ion signal without accumulating noise so that the signal/noise ratio is much improved provided that the "space-charge" limit of the total number of ions in the cell is not exceeded. "In-cell" ion accumulation allows selected ion accumulation by simply sweeping unwanted ions out of the cell prior to subsequent ion trapping events and also allows shifted ion accumulations to correct for time-of-flight distortions in the ion abundance distributions.

Heart failure caused by a novel amyloidogenic mutation of the transthyretin gene: ATTR Ala45Ser

Cardiac failure in transthyretin (TTR) amyloidosis patients has been shown to be caused by different mutations in the TTR gene. In the present case, a 73-year-old man from Northern Sweden was evaluated for heart failure. Amyloid deposits were found in subcutaneous fat and in intestinal biopsies. The presence of a variant form of TTR was detected in the plasma by electrospray ionisation mass spectrometry (ESI-MS). The mutation was located by single-strand conformation polymorphism (SSCP) analysis of the TTR gene where a band shift was seen in exon 2. Direct sequencing of exon 2 revealed a single base-pair substitution (G1724T). This transversion results in an amino acid substitution at codon 45, alanine to serine (ATTR Ala45Ser). Mass spectrometry analysis excluded that the variant is a polymorphism, since no similar shift in molecular weight has been present in more than 200 control samples. Congo red and immunostaining of duodenum biopsy specimens confirmed the presence of systemic ATTR amyloidosis, and clinical examination, including echocardiography, found evidence of a restrictive cardiomyopathy. He had 10 years previously been operated for a bilateral carpal tunnel syndrome, but otherwise no symptoms were present that could be attributed to his systemic amyloidosis. No axonal polyneuropathy was noted at nerve conduction studies. This novel mutation is the second amyloidogenic TTR mutation found in the Swedish population.