Characterization of Cardiac-Onset Initial Presentation in Friedreich Ataxia
David R. LynchS. H. SubramonyKimberly Y. LinKatherine D. MathewsSusan PerlmanGrace YoonChristian Rummey
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Friedreich ataxia is an autosomal recessive neurodegenerative disease, which is the most common cause of inherited ataxias.About 95% of the patients demonstrate an expansion of a GAA trinucleotide repeat in intron 1 of the FRDA gene on chromosome 9q13.This leads to reduced levels of frataxin which has an important role in iron homeostasis.Friedreich ataxia is the result of accumulation of iron in mitochondria leading to excess production of free radicals, defects in specific mitochondrial enzymes, enhanced sensitivity to oxidative stress, and eventually freeradical mediated cell death.Currently there is no effective therapy for the disease, but antioxidant therapy has shown promise especially in cardiac involvement.Early identification of individuals with Friedreich ataxia and precise characterization of impairments and functional limitations gain importance as symptomatic treatment, rehabilitation and genetic counseling are considered.Here, we present the clinical findings of five cases with Friedreich ataxia who had homozygous GAA trinucleotide expansion and emphasize that Friedreich ataxia should be considered in the differential diagnosis of cases who present with progressive ataxia.
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The discovery of the genetic cause of Friedreich ataxia has significantly affected our understanding of the disorder at both the clinical and basic science levels. Friedreich ataxia results from a deficiency of functional frataxin, a protein that appears to be involved in mitochondrial iron homeostasis. This leads to iron accumulation and mitochondrial abnormalities with consequent oxidant damage. The clinical spectrum of Friedreich ataxia has also expanded with the recognition of broader phenotypic features, including the absence of classical Friedreich ataxia features, later age at onset, and spasticity instead of ataxia. Although no proven therapy is yet available, antioxidants are a potential method for therapeutic intervention.
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Abstract Background: Friedreich ataxia is an autosomal recessive disorder caused by mutations in the frataxin gene, leading to reduced levels of the mitochondrial protein frataxin. Assays to quantitatively measure frataxin in peripheral blood have been established. To determine the validity of frataxin as a biomarker for clinical trials, we assessed frataxin in clinically affected tissue. Methods: In 7 patients with Friedreich ataxia, frataxin content was measured in blood and skeletal muscle before and after treatment with recombinant human erythropoietin, applying the electrochemiluminescence immunoassay. Results: We found frataxin content to be correlated in peripheral blood mononuclear cells and skeletal muscle in drug‐naive patients with Friedreich ataxia. The correlation of frataxin content in both compartments remained significant after 8 weeks of treatment. Skeletal‐muscle frataxin values correlated with ataxia using the Scale for the Assessment and Rating of Ataxia score. Conclusions: Our results endorse frataxin measurements in peripheral blood cells as a valid biomarker in Friedreich ataxia. © 2011 Movement Disorder Society
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Friedreich's ataxia is the most frequent inherited ataxia in Caucasians. It is caused by deficiency of frataxin, a highly conserved nuclear-encoded protein localized in mitochondria. The DNA abnormality found in 98% of Friedreich's ataxia chromosomes is the unstable hyperexpansion of a GAA triplet repeat in the first intron of the frataxin gene. Most patients are homozygous for this repeat expansion. The expanded GAA repeat causes frataxin deficiency because it interferes with the transcription of the gene by adopting a non-B (probably triple helical) structure. Longer repeats cause a more profound frataxin deficiency and are associated with earlier onset and increased severity of the disease. Molecular testing has shown that the phenotypic spectrum of Friedreich's ataxia is wider than previously thought. Up to 10% of patients with recessive or sporadic degenerative ataxia who do not fulfill the Friedreich's ataxia diagnostic criteria are homozygous for expanded alleles at the Friedreich's ataxia locus. Late age of onset, retained tendon reflexes, and lack of pyramidal signs are among the atypical features observed in some patients with a positive molecular test. Yeast cells deficient in the frataxin homologue accumulate iron in mitochondria and show increased sensitivity to oxidative stress. This suggests that Friedreich's ataxia is caused by mitochondrial dysfunction and free radical toxicity, with consequent mitochondrial damage, axonal degeneration, and cell death.
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Introduction: Friedreich ataxia (FRDA) is a multi-system autosomal-recessive disease, the most common one of the genetically inherited ataxias. FRDA occurs as a consequence of mutations in the frataxin gene, with an expansion of a GAA trinucleotide. Ataxia with vitamin E deficiency (AVED) is characterized clinically by neurological symptoms with often striking resemblance to those of Friedreich’s ataxia (FA) but serum concentrations of vitamin E are low. Aim of study: To study clinical and genetic features of the Friedreich’s ataxia and AVED patients in 44 Moroccan families. Patients and Methods: Retrospective series of 72 Moroccan patients displaying Friedreich’s ataxia syndrome was recruited over a period of 22 years (1987-2009). All patients had a clinical and ophtalmological examinations, 30 patients underwent electromyography, and CT scan was performed in 29 patients. GAA repeats in the frataxin gene and the 744 del A mutation α-TTP gene were performed in all patients. Results: 17 patients (24% of cases) had the 744 del A mutation in the α-TTP gene responsible of ataxia with vitamin E deficiency (AVED) phenotype. 55 patients (76% of cases) had GAA expanded allele in the first intron of the frataxin gene. Phenotype-genotype correlation revealed a high frequency of head titubation, decreased visual acuity and slower disease progression in AVED than in Friedreich’s ataxia phenotype (p Our study represents a large series which highlight the clinical and genetic differences between AVED and Friedreich’s ataxia. AVED patients have a better prognosis after alpha-tocopherol treatment.
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Friedreich's ataxia, the most common inherited ataxia, is associated with a mutation that consists of an unstable expansion of GAA repeats in the first intron of the frataxin gene on chromosome 9, which encodes a protein of unknown function.
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