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Background: Hereditary transthyretin amyloidosis (ATTR) is usually characterised by a progressive peripheral and autonomic neuropathy often with associated cardiac failure and is due to dominantly inherited transthyretin mutations causing accelerated amyloid deposition. The UK population is unique in that the majority of patients have the T60A missense mutation in ATTR where tyrosine is replaced by adenine at position 60. This has been traced to a single founder mutation from north-west Ireland. The neuropathy phenotype is less well described than the cardiac manifestations in this group.Methods: We present the findings from an observational cohort study of patients with ATTR attending the National Hospital Inherited Neuropathy Clinic between 2009 and 2013. Detailed clinical neurological and electrophysiological data were collected on all patients alongside correlating autonomic and cardiac assessments. Follow-up data were available on a subset.Results: Forty-four patients with genetically confirmed ATTR were assessed; 37 were symptomatic; mean age at onset=62 years, range=38-75 years; 75.7% male. T60A was the most common mutation (17/37), followed by V30M (5/37). A severe, rapidly progressive, predominantly length dependent axonal sensorimotor neuropathy was the predominant phenotype. T60A patients were distinguished by earlier and more frequent association with carpal tunnel syndrome; a predominance of negative sensory symptoms at onset; significant vibration deficits; and a non-length dependent progression of motor deficit. Progression of the neuropathy was observed over a relatively short follow-up period (2 years) in 20 patients with evidence of clinically measurable annual change in Medical Research Council (MRC) sum score (-1.5 points per year) and Charcot Marie Tooth Neuropathy Score (CMTNS:2.7 points per year), and a congruent trend in the electrophysiological measures used.Conclusion: The description of the ATTR neuropathy phenotype, especially in the T60A patients, should aid early diagnosis as well as contribute to the understanding of its natural history. [ABSTRACT FROM AUTHOR]

Background In overwork weakness (OW), muscles are increasingly weakened by exercise, work or daily activities. Although it is a well-established phenomenon in several neuromuscular disorders, it is debated whether it occurs in Charcot-Marie-Tooth disease (CMT). Dominant limb muscles undergo a heavier overload than non-dominant and therefore if OW occurs we would expect them to become weaker. Four previous studies, comparing dominant and non-dominant hand strength in CMT series employing manual testing or myometry, gave contradictory results. Moreover, none of them examined the behaviour of lower limb muscles. Methods We tested the OW hypothesis in 271 CMT1A adult patients by comparing bilateral intrinsic hand and leg muscle strength with manual testing as well as manual dexterity. Results We found no significant difference between sides for the strength of first dorsal interosseous, abductor pollicis brevis, anterior tibialis and triceps surae. Dominant side muscles did not become weaker than non-dominant with increasing age and disease severity (assessed with the CMT Neuropathy Score); in fact, the dominant triceps surae was slightly stronger than the non-dominant with increasing age and disease severity. Discussion Our data does not support the OW hypothesis and the consequent harmful effect of exercise in patients with CMT1A. Physical activity should be encouraged, and rehabilitation remains the most effective treatment for CMT patients. [ABSTRACT FROM AUTHOR]

Objectives: To analyse and describe the clinical and genetic spectrum of Charcot-Marie-Tooth disease (CMT) caused by mutations in the neurofilament light polypeptide gene ( NEFL )., Methods: Combined analysis of newly identified patients with NEFL -related CMT and all previously reported cases from the literature., Results: Five new unrelated patients with CMT carrying the NEFL mutations P8R and N98S and the novel variant L311P were identified. Combined data from these cases and 62 kindreds from the literature revealed four common mutations (P8R, P22S, N98S and E396K) and three mutational hotspots accounting for 37 (55%) and 50 (75%) kindreds, respectively. Eight patients had de novo mutations. Loss of large-myelinated fibres was a uniform feature in a total of 21 sural nerve biopsies and 'onion bulb' formations and/or thin myelin sheaths were observed in 14 (67%) of them. The neurophysiological phenotype was broad but most patients with E90K and N98S had upper limb motor conduction velocities <38 m/s. Age of onset was ≤3 years in 25 cases. Pyramidal tract signs were described in 13 patients and 7 patients were initially diagnosed with or tested for inherited ataxia. Patients with E90K and N98S frequently presented before age 3 years and developed hearing loss or other neurological features including ataxia and/or cerebellar atrophy on brain MRI., Conclusions: NEFL -related CMT is clinically and genetically heterogeneous. Based on this study, however, we propose mutational hotspots and relevant clinical-genetic associations that may be helpful in the evaluation of NEFL sequence variants and the differential diagnosis with other forms of CMT., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Myelin protein zero (MPZ) is a major component of compact myelin in peripheral nerves where it plays an essential role in myelin formation and adhesion. MPZ gene mutations are usually responsible for demyelinating neuropathies, namely Charcot-Marie-Tooth (CMT) type 1B, Déjèrine-Sottas neuropathy and congenital hypomyelinating neuropathy. Less frequently, axonal CMT (CMT2) associated with MPZ mutations has been described. We report six patients (one sporadic case and five subjects from two apparently unrelated families) with a late onset, but rapidly progressive, axonal peripheral neuropathy. In all patients, molecular analysis demonstrated a novel heterozygous missense mutation (208C>T) in MPZ exon 2, causing the Pro70Ser substitution in the extracellular domain. The diagnosis of CMT2 associated with MPZ mutations should be considered in both sporadic and familial cases of late onset, progressive polyneuropathy. The mechanism whereby compact myelin protein mutations cause axonal neuropathy remains to be elucidated.