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Objective: We sought to define the significance of brachial amyotrophic diplegia (flail arm syndrome [FA]) and the pseudopolyneuritic variant (flail leg syndrome [FL]) of amyotrophic lateral sclerosis (ALS; motor neuron disease). Methods:We analyzed survival in clinic cohorts in London, UK (1,188 cases), and Melbourne, Australia (432 cases). Survival from disease onset was analyzed using the Kaplan-Meier method and Cox proportional hazards model. Results:In the London cohort, the FA syndrome represented 11% and the FL syndrome 6% of the sample. Median survival was 35 months for limb onset and 27 months for bulbar onset ALS, whereas this was 61 months for FA syndrome (p Ͻ 0.001) and 69 months for FL syndrome (p Ͻ 0.001). Five-year survival in this cohort was 8.8% for bulbar onset, 20% for limb onset, 52% for FA syndrome, and 64% for FL syndrome. The ratio of men to women was 4:1 in the FA group compared to 2:1 in other limb onset cases. Excluding lower motor neuron FA and FL cases, progressive muscular atrophy comprised 4% of the sample and had a prognosis similar to typical limb onset ALS. In the Melbourne cohort, median survival for limb onset ALS was 31 months, bulbar onset 27 months, FA syndrome 66 months (p Ͻ 0.001), and FL syndrome 71 months (p ϭ 0.001). Amyotrophic lateral sclerosis (ALS) comprises several clinical phenotypes united by a common cellular and molecular pathology. Conclusions:1 The three main clinical categories defined by Aran, Charcot, Duchenne, and others in the 19th century and which were subsequently shown to have both diagnostic and prognostic significance were progressive bulbar palsy (bulbar onset ALS), classic limb onset (Charcot) ALS, and a lower motor neuron form termed progressive muscular atrophy (PMA).2-5 Prognostic factors in these forms of ALS have been delineated through clinic and population-based studies. 6,7 Bulbar onset tends to have a worse prognosis than limb onset, and both forms have a worse prognosis than PMA.2,4-7 However, these three phenotypic categories do not fully capture the spectrum of clinical heterogeneity in ALS. This heterogeneity may contribute to diagnostic error and delay, and with the advent of large-scale whole genome studies that have the potential to identify genetic variants influencing both risk and phenotype,

One hundred and fifty years since Nikolaus Friedreich's first description of the degenerative ataxic syndrome which bears his name, his description remains at the core of the classical clinical phenotype of gait and limb ataxia, poor balance and coordination, leg weakness, sensory loss, areflexia, impaired walking, dysarthria, dysphagia, eye movement abnormalities, scoliosis, foot deformities, cardiomyopathy and diabetes. Onset is typically around puberty with slow progression and shortened life-span often related to cardiac complications. Inheritance is autosomal recessive with the vast majority of cases showing an unstable intronic GAA expansion in both alleles of the frataxin gene on chromosome 9q13. A small number of cases are caused by a compound heterozygous expansion with a point mutation or deletion. Understanding of the underlying molecular biology has enabled identification of atypical phenotypes with late onset, or atypical features such as retained reflexes. Late-onset cases tend to have slower progression and are associated with smaller GAA expansions. Early-onset cases tend to have more rapid progression and a higher frequency of non-neurological features such as diabetes, cardiomyopathy, scoliosis and pes cavus. Compound heterozygotes, including those with large deletions, often have atypical features. In this paper, we review the classical and atypical clinical phenotypes of Friedreich's ataxia.

BackgroundThe European Friedreich's Ataxia Consortium for Translational Studies (EFACTS) is a prospective international registry investigating the natural history of Friedreich ataxia (FRDA). We report one-and two-year longitudinal data to delineate potential outcomes for clinical trials. MethodsWe enrolled genetically confirmed FRDA patients from eleven European study sites. Patients were seen on an annual basis at three visits. Our primary endpoint was the Scale for the Assessment and Rating of Ataxia (SARA). Secondary outcomes were the Inventory of Non-Ataxia Signs (INAS), the Spinocerebellar Ataxia Functional Index (SCAFI), phonemic verbal fluency (PVF) and the quality of life measures activities of daily living (ADL) and EQ-5D-3L index. Disease progression was analyzed with linear mixed effect models. This study is registered with ClinicalTrials.gov, number NCT02069509. Patients with more than 353 GAA repeats on the shorter allele had a higher SARA progression rate (by 0·09 [0·02] per additional 100 repeats). Annual worsening for INAS was 0·10 (0·03), for SCAFI -0·04 (0·01), for ADL 0·93 (0·06) and for EQ-5D-3L -0·02 (0·004). PVF performance improved by 0·99 [0·14] words per year. 548 or 184 patients would be needed to detect a 50% reduction in SARA progression at 80% power in a one-year or two-year clinical trial, respectively. InterpretationThe EFACTS longitudinal analysis provides suitable outcome measures and sample size calculation for upcoming clinical trial designs in FRDA.

In compound heterozygotes, expression of partially functional mutant frataxin delays age of onset and reduces diabetes mellitus, compared to those with no frataxin expression from the non-expanded allele. This integrated analysis of categorized frataxin mutations and their correlation with clinical outcome provide a definitive resource for investigating disease pathogenesis in FRDA.

Ataxia UK, Ataxia Ireland, Association Suisse de l'Ataxie de Friedreich, Associazione Italiana per le Sindromi Atassiche, UK National Institute for Health Research, European Friedreich's Ataxia Consortium for Translational Studies, and Imperial Biomedical Research Centre.