Transthyretin familial amyloid polyneuropathy (TTR-FAP) classically presents as a length dependent small fiber polyneuropathy in endemic countries like Portugal. In nonendemic countries, it may mimic a variety of chronic polyneuropathies, with several phenotypes: ataxic, upper limb onset neuropathy, or motor. In these cases, there is usually a late onset and no positive family history. TTR gene sequencing appears the most pertinent first-line test for diagnosis. Cardiac involvement of various severities is common in FAP. Liver transplantation remains the standard antiamyloid therapy with better results in Val30Met TTR-FAP of early onset. Antiamyloid medication has been developed. (1) TTR stabilizers: Tafamidis was the first drug approved in Europe in stage 1 (walking unaided) TTR-FAP to slow progression of the disease; diflunisal has been assessed in a phase 3 clinical trial; (2) TTR gene silencing is a new strategy to inhibit production of both mutant and nonmutant TTR with antisense oligonucleotides or SiRNA (2 ongoing phase 3 clinical trials).

FAP neuropathy and emerging treatments.

Transthyretin-related familial amyloidotic polyneuropathy (TTR-FAP) usually presents itself as a progressive sensorimotor polyneuropathy with severe autonomic dysfunction and cardiomyopathy. Eighteen patients carrying the Leu64 mutation underwent a series of regular follow-ups, including: neurological examination, electroneurography, electromyography, electrocardiography and echocardiography, blood analysis, a questionnaire on autonomic symptoms, cardiovascular autonomic tests and a 99mTc-DPD examination study. A late onset of a slowly progressive disease which reached its terminal stage after about 10  years was observed. The onset was mainly a length-dependent sensory neuropathy, although a focal onset with carpal tunnel syndrome was detected in three patients. At the onset of the disease, autonomic dysfunction was present in a small number of patients, but, within a few years, this had manifested in all members of the sample group. The only extra-neurological manifestations were cardiac related. It is reasonable to consider Southern Italy as an endemic focus of TTR-FAP. An underestimation of disease prevalence could be caused by a late onset of FAP, which can manifest in patients up to their late 70s. Follow-up of asymptomatic individuals may permit the early detection of symptoms and signs, allowing a detailed record of the natural history of the disease from the beginning and facilitating prompt treatment.

Transthyretin‐related familial amyloidotic polyneuropathy: description of a cohort of patients with Leu64 mutation and late onset

Objective: Familial amyloid polyneuropathy (FAP) is typically a predominantly sensory and autonomic neuropathy with progressive and late motor involvement leading to death within 10 years. Recently, prognosis was transformed with liver transplantation. Methods: We report an atypical sporadic pure motor and bulbar neuropathy initially mistaken for amyotrophic lateral sclerosis (ALS) in a 50-year-old Malian man. Results: The diagnostic procedure of this clinical purely motor and bulbar neuropathy disclosed amyloid deposits on nerve biopsy which led to the identification of a new Val93Met mutation of transthyretin. This case was also remarkable by its slow progression. Conclusions: This report confirms the motor phenotype of TTR-FAP. That should be considered in the differential diagnosis of motor neuron diseases in order to start accurate therapy. Abbreviations: ALS, amyotrophic lateral sclerosis; CIDP, chronic inflammatory demyelinating polyneuropathy; FAP, familial amyloid polyneuropathy; MRC, medical research council; PMA, progressive muscular atrophy; SALS, sporadic amyotrophic lateral sclerosis; SBMA, spino bulmbar muscular atrophy; TTR, transthyretin

An amyotrophic lateral sclerosis-like syndrome revealing an amyloid polyneuropathy associated with a novel transthyretin mutation.

Amyloid neuropathies of acquired or genetic origin are disabling and life-threatening, until recently there were few treatment options available. Poor prognosis is related to progressive neuropathy and associated, although often underdiagnosed, cardiac involvement in specific transthyretin (TTR) gene mutations. Recent progress has modified prognosis and management of amyloid neuropathies. In TTR-familial amyloidosis with polyneuropathy, major changes have occurred over the last 30 years: better knowledge concerning genetics, phenotypes and epidemiology, and the advent of possible treatments. Liver transplantation, first performed in 1990, stopped disease progression, thus doubling survival in early onset V30M patients. More recently tetramer stabilizers (Tafamidis and Diflunisal) showed a significant reduction of progression of neuropathic scores; Tafamidis is now recommended in Stage I patients. Two multicentric clinical trials are now ongoing to evaluate TTR gene silencing by antisense Oligonucleotides (ASO) or siRNA. In the near future we should have new therapeutical options for patients with amyloid neuropathy.

Current and future treatment of amyloid neuropathies.

Hereditary transthyretin amyloidosis (ATTRv) is a severe, adult-onset autosomal dominant inherited systemic disease predominantly affecting the peripheral and autonomic nervous system, heart, kidney and the eyes. ATTRv is caused by mutations of the transthyretin (TTR) gene, leading to extracellular deposition of amyloid fibrils in multiple organs including the peripheral nervous system. Typically, the neuropathy associated with ATTRv is characterised by a rapidly progressive and disabling sensorimotor axonal neuropathy with early small-fibre involvement. Carpal tunnel syndrome and cardiac dysfunction frequently coexist as part of the ATTRv phenotype. Although awareness of ATTRv polyneuropathy among neurologists has increased, the rate of misdiagnosis remains high, resulting in significant diagnostic delays and accrued disability. A timely and definitive diagnosis is important, given the emergence of effective therapies which have revolutionised the management of transthyretin amyloidosis. TTR protein stabilisers diflunisal and tafamidis can delay the progression of the disease, if treated early in the course. Additionally, TTR gene silencing medications, patisiran and inotersen, have resulted in up to 80% reduction in TTR production, leading to stabilisation or slight improvement of peripheral neuropathy and cardiac dysfunction, as well as improvement in quality of life and functional outcomes. The considerable therapeutic advances have raised additional challenges, including optimisation of diagnostic techniques and management approaches in ATTRv neuropathy. This review highlights the key advances in the diagnostic techniques, current and emerging management strategies, and biomarker development for disease progression in ATTRv.

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Novel approaches to diagnosis and management of hereditary transthyretin amyloidosis

131 HA-TTR patients from a single referral centre presented at onset five major clinical syndromes: (1) the typical "Portuguese variant" axonal polyneuropathy with dissociated (syringomyelic like) sensory loss and autonomic dysfunction; (2) bilateral carpal tunnel syndrome; (3) restless leg syndrome with impotence and unexplained loss of weight; (4) pure motor neuropathy without autonomic abnormalities; (5) recurrent small brain or spinal cord ischemia or haemorrhages with leptomeningeal amyloid deposition (and late superficial siderosis of the central nervous system) and vitreous deposits. Some patients in our population presented a "pseudodemyelinating" onset of the somatic neuropathy, as well as atypical motor neuropathy simulating lower motor neuron disease. The five syndromes can overlap in advanced stages of the disease. Genetic screening of HA-TTR could be worthwhile in any idiopathic progressive axonal peripheral neuropathy, as well as in drug resistant demyelinating sensory-motor neuropathy or in pure motor neuropathy, when multi-organ involvement is present.

Genotypic and phenotypic correlation in an Italian population of hereditary amyloidosis TTR-related (HA-TTR): clinical and neurophysiological aids to diagnosis and some reflections on misdiagnosis.

Illaria Bartolomei

Papers

Genotypic and phenotypic correlation in an Italian population of hereditary amyloidosis TTR-related (HA-TTR): clinical and neurophysiological aids to diagnosis and some reflections on misdiagnosis.