Type I familial amyloidotic polyneuropathy in Japan

Hereditary transthyretin-related amyloidosis

Hereditary transthyretin(TTR)-related amyloidosis (ATTRm amyloidosis) is an endemic/non-endemic, autosomal-dominant, early- and late-onset, rare, progressive disorder, predominantly manifesting as length-dependent, small fiber dominant, axonal polyneuropathy and frequently associated with cardiac disorders and other multisystem diseases. ATTRm amyloidosis is due to variants in the TTR gene, with the substitution Val30Met as the most frequent mutation. TTR mutations lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, and formation of amyloid fibrils, which are consecutively deposited extracellularly in various tissues, such as nerves, heart, brain, eyes, intestines, kidneys, or the skin. Neuropathy may not only include large nerve fibers but also small fibers, and not only sensory and motor fibers but also autonomic fibers. Types of TTR variants, age at onset, penetrance, and clinical presentation vary between geographical areas. Suggestive of a ATTRm amyloidosis are a sensorimotor polyneuropathy, positive family history, autonomic dysfunction, cardiomyopathy, carpal tunnel syndrome, unexplained weight loss, and resistance to immunotherapy. If only sensory A-delta or C fibers are affected, small fiber neuropathy ensues. Diagnostic tests for small fiber neuropathy include determination of intraepidermal nerve fiber density, laser-evoked potentials, heat- and cold-detection thresholds, and measurement of the electrochemical skin conductance. Therapy currently relies on liver transplantation and TTR-stabilizers (tafamidis, diflunisal).

Diagnosis and management of transthyretin familial amyloid polyneuropathy in Japan: red-flag symptom clusters and treatment algorithm

Hereditary ATTR (ATTRm) amyloidosis (also called transthyretin-type familial amyloid polyneuropathy [ATTR-FAP]) is an autosomal-dominant, adult-onset, rare systemic disorder predominantly characterized by irreversible, progressive, and persistent peripheral nerve damage. TTR gene mutations (e.g. replacement of valine with methionine at position 30 [Val30Met (p.Val50Met)]) lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, which form amyloid fibrils that deposit in peripheral nerves and various organs, giving rise to peripheral and autonomic neuropathy and several non-disease specific symptoms.

Phenotypic and genetic variability and non–disease-specific symptoms often delay diagnosis and lead to misdiagnosis. Red-flag symptom clusters simplify diagnosis globally. However, in Japan, types of TTR variants, age of onset, penetrance, and clinical symptoms of Val30Met are more varied than in other countries. Hence, development of a Japan-specific red-flag symptom cluster is warranted. Presence of progressive peripheral sensory-motor polyneuropathy and ≥1 red-flag sign/symptom (e.g. family history, autonomic dysfunction, cardiac involvement, carpal tunnel syndrome, gastrointestinal disturbances, unexplained weight loss, and immunotherapy resistance) suggests ATTR-FAP. Outside of Japan, pharmacotherapeutic options are first-line therapy. However, because of positive outcomes (better life expectancy and higher survival rates) with living donor transplant in Japan, liver transplantation remains first-line treatment, necessitating a Japan-specific treatment algorithm.

Herein, we present a consolidated review of the ATTR-FAP Val30Met landscape in Japan and summarize findings from a medical advisory board meeting held in Tokyo on 18th August 2016, at which a Japan-specific ATTR-FAP red-flag symptom cluster and treatment algorithm was developed. Beside liver transplantation, a TTR-stabilizing agent (e.g. tafamidis) is a treatment option. Early diagnosis and timely treatment using the Japan-specific red-flag symptom cluster and treatment algorithm might help guide clinicians regarding apt and judicious use of available treatment modalities.

Diagnosis of familial amyloid polyneuropathy: wide-ranged clinicopathological features

IMPORTANCE OF THE FIELD

Owing to the recent development of biochemical and molecular analyses, familial amyloid polyneuropathy (FAP) is not considered to be as rare as was previously thought. Transthyretin (TTR) Val30Met-associated FAP (FAP ATTR Val30Met) is the most common form of FAP. Although patients with FAP ATTR Val30Met had been considered to be concentrated in geographically restricted areas of Japan, Portugal and Sweden, a late-onset form of this type of FAP was discovered in non-endemic areas and revealed to be widely distributed throughout the world. Therefore, there is an increasing necessity to characterize the variability in the clinical, electrophysiological and histopathological features of this disease.

AREAS COVERED IN THIS REVIEW

Recent progress in the diagnostic techniques for FAP is described, focusing especially on those for FAP ATTR Val30Met. Clinical, electrophysiological and histopathological features in early-onset FAP ATTR Val30Met cases from endemic foci and those in late-onset cases from non-endemic areas in Japan are comparatively described.

WHAT THE READER WILL GAIN

Patients with FAP ATTR Val30Met from endemic foci and those from non-endemic areas show different clinical, electrophysiological and histopathological features. As compared with the classic FAP phenotype, the clinicopathological features of patients from the non-endemic areas tend to be nonspecific.

TAKE HOME MESSAGE

Awareness of the possibility of sporadic late-onset FAP ATTR Val30Met is needed at the time of the initial clinical and electrophysiological evaluation of neuropathy with an undetermined etiology to avoid a missed diagnosis.

Familial amyloidotic polyneuropathy and transthyretin

There has been much progress in our understanding of transthyretin (TTR)-related amyloidosis including familial amyloidotic polyneuropathy (FAP), senile systemic amyloidosis and its related disorders from many clinical and experimental aspects. FAP is an inherited severe systemic amyloidosis caused by mutated TTR, and characterized by amyloid deposition mainly in the peripheral nervous system and the heart. Liver transplantation is the only available treatment for the disease. FAP is now recognized not to be a rare disease, and to have many variations based on genetical and biochemical variations of TTR. This chapter covers the recent advances in the clinical and pathological aspects of, and therapeutic approaches to FAP, and the trend as to the molecular pathogenesis of TTR.

Diagnosis of sporadic transthyretin Val30Met familial amyloid polyneuropathy: a practical analysis

Transthyretin (TTR) Val30Met-associated familial amyloid polyneuropathy (FAP ATTR Val30Met) is the most common form of FAP and is now prevalent in areas other than those seen within conventional endemic foci. We investigated 15 patients with FAP ATTR Val30Met without a family history of FAP who were referred for sural nerve biopsy. Initial symptoms included somatic neuropathy in all patients, while sensory dissociation and autonomic symptoms were apparent only in two and seven patients, respectively. Nonspecific neuropathic features and slight abnormalities in cerebrospinal fluid protein levels and in electrophysiological indices related to nerve conduction led clinicians to initially suspect chronic inflammatory demyelinating polyneuropathy (CIDP) in some patients. Small-fiber predominant loss was observed in a minority of patients. In terms of cardiac involvement, findings suggestive of subclinical cardiomyopathy due to amyloid deposition, such as cardiomegaly on chest X-ray, thickening of the interventricular septum, and granular sparkling echo on echocardiography, were seen alone or in combination in 11 of 14 examined patients. In conclusion, clinicians should consider the possibility of FAP ATTR Val30Met in patients presenting with neuropathy of undetermined etiology to avoid misdiagnosis. Detecting subclinical cardiac involvement may help to diagnose late-onset FAP ATTR Val30Met in those without a family history of the disease.

Distinct characteristics of amyloid deposits in early- and late-onset transthyretin Val30Met familial amyloid polyneuropathy

Late-onset transthyretin Val30Met-associated familial amyloid polyneuropathy (FAP ATTR Val30Met) cases unrelated to endemic foci in Japan show different clinicopathological features from the conventional early-onset cases in endemic foci. We compared the characteristics of amyloid deposits in early-onset FAP ATTR Val30Met cases in endemic foci and late-onset cases in non-endemic areas. Amyloid deposits in three early-onset cases from endemic foci and five late-onset cases from non-endemic areas were systematically examined post-mortem. Amyloid deposits in early-onset cases were highly congophilic and showed strong apple-green birefringence with Congo red staining and had long, parallel fibrils in most organs. On the other hand, those in late-onset cases were generally weakly congophilic and showed faint apple-green birefringence with Congo red staining and had short, haphazard fibrils. In the renal glomus and adrenal gland of early-onset cases, the characteristics of amyloid deposits were similar to those observed in late-onset cases. Analysis of cardiac amyloid using surface enhanced desorption/ionization time-of-flight mass spectrometry indicated that most transthyretin (TTR) was variant in early-onset cases, while more than half was composed of wild-type TTR in late-onset cases. Although characteristics of amyloid deposits may differ among individual organs of respective cases, especially in early-onset cases, the pattern was distinct between early- and late-onset cases. Amyloid deposition in late-onset cases may be similar to that observed in senile systemic amyloidosis with wild-type TTR deposition, suggesting that aging may play an important role in these cases.

Clinical and histopathological features of progressive-type familial amyloidotic polyneuropathy with TTR Lys54

The purpose of this study was to evaluate the clinical and pathological features in patients with progressive-type familial amyloidotic polyneuropathy (FAP) using autopsy and biopsy specimens. A proband is a 33-year-old man with FAP type I who developed motor, sensory and autonomic impairments with neuropathy, heart failure, and anorexia. Genetic findings of transthyretin (TTR) revealed G to A transition in codon 54 causing a rare mutation of TTR Lys54. He died of pneumonia and severe cardiac failure 4 years after onset. Autopsy showed heavy amyloid deposition in the heart, peripheral nerves, thyroid, skin, fat tissue, prostate and testis, moderate in the sympathetic nerve trunk, vagal nerve, celiac plexus, pelvic plexus, bladder, gastrointestinal tract, tongue, pancreas, lung, pituitary, blood vessel, gall bladder, adrenals and muscles, and free in the central nervous system, liver, kidney and spleen. Sural nerve biopsy in a sibling confirmed TTR amyloidosis immunohistochemically. Electronmicroscopic findings of amyloid fibrils were similar to that of FAP Met30. Immunoelectronmicroscopic findings indicated the relationship between amyloid fibrils or non-fibrillar structure and collagen fibers. The distribution of amyloid deposition, heavy in the heart and lacking in the kidney, is a characteristic feature and reflected severity of FAP with TTR Lys54.

Transthyretin and familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is an inherited autosomal dominant disease that is commonly caused by accumulation of deposits of transthyretin (TTR) amyloid around peripheral nerves. The only effective treatment for FAP is liver transplantation. However, recent studies on TTR aggregation provide clues to the mechanism of the molecular pathogenesis of FAP and suggest new avenues for therapeutic intervention. It is increasingly recognized that there are common features of a number of protein-misfolding diseases that can lead to neurodegeneration. As for other amyloidogenic proteins, the most toxic forms of aggregated TTR are likely to be the low-molecular-mass diffusible species, and there is increasing evidence that this toxicity is mediated by disturbances in calcium homeostasis. This article reviews what is already known about the mechanism of TTR aggregation in FAP and describes how recent discoveries in other areas of amyloid research, particularly Alzheimer's disease, provide clues to the molecular pathogenesis of FAP.

Cardiac amyloidosis associated with a novel transthyretin aspartic acid-18 glutamic acid de novo mutation

A 40-year-old man presented with initial symptoms of syncope caused by restrictive cardiomyopathy and autonomic nervous system impairment, but it was confirmed that he had a novel transthyretin (TTR) variant, aspartic acid-18 glutamic acid (Glu), and a de novo gene mutation. A polymerase chain reaction-induced mutation restriction analysis with a mismatched sense primer demonstrated that he was heterozygous for TTR Glu 18. Liver transplantation was not performed because of profound weakness and severe postural hypotension. Right-sided heart failure predominated in association with low output syndrome and a gradual decrease in total QRS voltage on electrocardiogram over 5 years of follow-up. Autonomic neuropathy developed and he eventually died of both-sided heart failure at the age of 45 years. Immunohistochemical and DNA studies are important to diagnose and treat TTR-related cardiac amyloidosis.

A severe form of amyloidotic polyneuropathy in a Costa Rican family with a rare transthyretin mutation (Glu54Lys)

Four affected siblings in a Costa Rican family presented an aggressive polyneuropathy with widespread involvement of many visceral organs and onset during the third decade of life with rapid loss of muscle mass in the lower limbs and severe dysautonomy. The medical histories include vitreous opacity, cardiac enlargement, dermal and gastrointestinal infiltration, and autonomic dysfunction including circulatory compromise and gastrointestinal disturbances. Histological studies using Congo red stain and immunohistochemical assays with antibodies against the transthyretin (TTR) protein showed widespread deposition of amyloid in extracellular areas, including dermis and gastrointestinal lamina propia, endo- and perineural spaces, and vascular walls. A mutation search in the transthyretin (ttr) gene was performed seeking the cause of this severe form of familial amyloidotic polyneuropathy (FAP). We applied single-stranded conformational polymorphism (SSCP)-analyses followed by sequencing of the four exons of the ttr gene, revealing a point mutation in exon 3, a G to A transition that causes a Glu54Lys codon change. Western blots of plasma proteins incubated with anti-transthyretin antibodies after gel electrophoresis provided separation of wild-type and mutant TTR protein in affected family members.

Late-onset familial amyloid polyneuropathy: an autopsy study of two Japanese brothers

We report an autopsy study of late-onset familial amyloid polyneuropathy with a variant transthyretin Val30Met in 2 brothers living in Kyoto, Japan. The disease onsets were at 64 and 59 years, and they died at 71 and 74 years old, respectively. They exhibited almost the same postmortem findings. Amyloid deposition was remarkable in the hearts, but was not seen in the renal glomeruli. In the peripheral nervous system, amyloid deposition was most prominent in the nerves immediately caudal to ganglia, moderate in the dorsal and sympathetic ganglia, and mild in the spinal roots, sciatic nerves, and distal nerves. The difference between the amyloid deposition in the proximal portion and distal portion of the extremity nerves appeared to be greater in the late-onset type than in the ordinary type, and this proximal deposition of amyloid may have induced severe distal nerve fiber degeneration.

Effect of the intestinal flora on amyloid deposition in a transgenic mouse model of familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is a hereditary disease characterized by the systemic accumulation of amyloid fibrils. A mutant transthyretin (TTR) gene is mainly responsible for the disease. However, the variable age of onset and low penetrance might be due to environmental factors, one of which is the intestinal flora. Three types of intestinal flora were introduced into a transgenic (Tg) mouse FAP model, 6.0-hMet30. The CV1 and CV2 group transgenic mice were transferred with the intestinal flora from two different mouse facilities housed under conventional conditions, and the SPF group transgenic mice were kept under specific pathogen free conditions in our facility. All the mice were maintained under controlled temperature, humidity and bacterial conditions. Over a period of 28 months, amyloid was not deposited in the SPF and CV1 groups. In contrast, amyloid was deposited in the esophagus and small intestine of two of the three CV2 mice at 18 months. Many neutrophils infiltrated the lesions. The numbers of tissue neutrophils were higher in the CV2 group than in the SPF and CV1 groups at 18 months. The CV2 flora included fewer gram-positive anaerobic cocci as well as higher proportions of yeasts, staphylococci and enterobacteriaceae compared with the SPF and CV1 flora. These findings suggest that the intestinal flora plays an important role in amyloid deposition.

A case of late onset cardiac amyloidosis with a new transthyretin variant (lysine 92)

A new transthyretin (TTR) variant (lysine 92), which causes late onset cardiac amyloidosis, is described in a 71-year-old man. The patient at first had syncope due to ventricular tachycardia and was admitted our hospital. Typical findings of cardiac amyloidosis were observed by echocardiography, and a diagnosis of systemic amyloidosis was made by rectal biopsy. The man died approximately 3 years and 6 months after first admission, with gradually worsening congestive heart failure. Pathological examination showed prominent amyloid deposits in the heart and the vascular wall of many organs including the liver, pancreas, kidney, lung, and gastrointestinal tracts. Amyloid protein of transthyretin type was indicated by immunohistochemical study, and DNA sequencing identified a novel mutation in the transthyretin gene encoding 92 glutamine --> lysine. A polymerase chain reaction-induced mutation restriction analysis with a mismatched antisense primer showed that the patient was heterozygous for the TTR Lys92 allele.

Familial amyloidotic polyneuropathy type 1 in Brazil is associated with the transthyretin Val30Met variant

Familial amyloidotic polyneuropathy type 1 (FAP1) is an inherited systemic amyloidosis that is secondary to the deposition of transthyretin (TTR) variants in peripheral nerves and in certain visceral organs. More than 50 distinct mutations have already been described in the TTR gene. Yet, the most common mutation found worldwide is a substitution of valine for methionine in position 30 (Val30Met). Currently, the variants of TTR in Brazilian FAP1 patients remain largely unknown and the aim of this study was to analyze the frequency of the TTR Val30Met mutation in such Brazilian subjects.

METHODS

Thirty-two FAP1 patients belonging to 24 different families were studied for the presence of Val30Met variant by PCR-RFLP.

RESULTS

All Brazilian FAP1 subjects studied were positive for the TTR Val30Met variant. As expected, all of them were heterozygous for the mutation.

CONCLUSION

TTR Val30Met mutation was the sole TTR variant found in Brazilian FAP1 patients in this cohort, and it was present even in those subjects without a clear history of Portuguese ancestry.

Late-onset familial amyloid polyneuropathy type I (transthyretin Met30-associated familial amyloid polyneuropathy) unrelated to endemic focus in Japan. Clinicopathological and genetic features

Clinicopathological and genetic features were assessed on 35 Japanese families affected by late-onset familial amyloid polyneuropathy type I (transthyretin Met30-associated familial amyloid polyneuropathy, FAP TTR Met30) whose siblings were unrelated to endemic Japanese foci. In these patients (50 years or older), the most common initial symptom was paraesthesias in the legs. Autonomic symptoms were generally mild and did not seriously affect daily activities. The male-to-female ratio was extremely high (10.7 : 1). A family history was evident in only 11 out of 35 families, and other patients were apparently sporadic. The rate of penetrance was very low. Symptomatic siblings of familial cases showed a late age of onset, male preponderance and clinical features similar to those of the probands. Asymptomatic carriers, predominantly female, were detected relatively late in life. The geographical distribution of these late-onset, FAP TTR Met30 cases was scattered throughout Japan. In three autopsy cases and 20 sural nerve biopsy specimens, neurons in sympathetic and sensory ganglia were relatively preserved. Amyloid deposition was seen in the peripheral nervous system, particularly in the sympathetic ganglia, dorsal root ganglia and proximal nerve trunks such as sciatic nerve. These abnormalities were milder than those seen in typical early-onset FAP TTR Met30, as observed in two Japanese endemic foci of this disease. While axonal degeneration was prominent in myelinated fibres, resulting in severe fibre loss, unmyelinated fibres were relatively preserved. Our cases of late-onset FAP TTR Met30 showed features distinct from those of typical early-onset FAP TTR Met30 that occurred in the two Japanese endemic foci. Factors responsible for clinicopathological differences between these two forms of FAP TTR Met30 need to be identified.

A case of hereditary amyloidosis transthyretin variant Met 30 with amyloid cardiomyopathy, less polyneuropathy, and the presence of giant cells

Transthyretin-Met 30 (TTR-Met 30) is a variant of transthyretin and is usually associated with familial amyloid polyneuropathy. It is rare that patients with TTR-Met 30 will primarily develop amyloid cardiomyopathy. This report presents a patient with late-onset TTR-Met 30 who primarily developed amyloid cardiomyopathy, with less amyloid polyneuropathy in the peripheral nervous system than is usually seen. An autopsy was performed, and histological examination revealed many foreign-body giant cells and macrophages in the area of amyloid deposition that was found in nearly all of the organs.

Investigation into thiol conjugation of transthyretin in hereditary transthyretin amyloidosis

BACKGROUND

For all forms of amyloidosis, the amyloid-generating mechanism is unknown. Familial amyloidotic polyneuropathy type I is caused by a variant transthyretin (TTR Met-30). As electrospray ionization mass spectrometry (ESI-MS) discloses both thiol-conjugated and -unconjugated forms of wild-type and variant TTR, we wanted to investigate the relationship between TTR conjugation and clinically overt amyloid disease.

METHODS

Plasma from 35 individuals (12 symptomatic TTR Met-30 carriers, nine asymptomatic and 14 healthy control subjects) were analysed using ESI-MS.

RESULTS

The total TTR concentration was significantly lower in symptomatic TTR Met-30 carriers than in control subjects. An increased percentage of conjugated TTR Met-30 was found in symptomatic carriers compared with asymptomatic, whereas the percentage conjugated wild-type TTR was similar for control subjects, asymptomatic and symptomatic TTR Met-30 carriers.

CONCLUSION

The finding of a decreased ratio of unconjugated to conjugated TTR Met-30 in plasma samples from symptomatic TTR Met-30 carriers indicates that thiol conjugation of TTR could be involved in amyloid formation.