Friedreich ataxia with minimal GAA expansion presenting as adult-onset spastic ataxia.

Around a quarter of Friedreich ataxia (FA) patients, despite being homozygous for GAA expansion within the FRDA gene, show atypical presentations. Our aim is to describe the case of three brothers with long-term follow-up suffering from late onset FA manifested with spastic ataxia. The three patients belong to a family with occipital dysplasia (OD) and Chiari I malformation previously reported by us. We have carried out serial examinations since 1977. Electrophysiological and neuroimaging studies, and molecular genetic analyses of hereditary ataxias are available in all three patients. Onset of symptoms occurred between 25 and 35 years. The clinical picture consisted of progressive spastic gait, truncal and limb ataxia, dysarthria, nystagmus, hyperreflexia with knee and ankle clonus and extensor plantar response, and mild hypopallesthesia. Ages at present vary between 50 and 59. One patient is wheelchair-bound but the other two are able to walk with support. Leaving OD aside, skeletal anomalies are not prominent. All three patients showed cardiomyopathy. MR imaging revealed atrophy of the cerebellum and spinal cord. Motor and sensory nerve conduction velocities were normal. Central conduction time of both motor and sensory pathways was delayed or unobtainable. All three patients were homozygous for the GAA expansion, the smaller expanded allele ranging between 131 and 156 repeats. Four heterozygotic carriers were detected among non-ataxic relatives including one with OD; furthermore, an asymptomatic OD patient showed normal genotype. We conclude that adult onset spastic ataxia is a distinctive FA phenotype associated with minimal GAA expansion. This phenotype represents a new cause of selective distal degeneration of central sensory axons. The present concurrence of OD and FA reflects coincidental cosegregation of two different inherited disorders.     

GAA trinucleotide repeat expansion in variant Friedreich's ataxia families

Phenotypic variants in Friedreich's ataxia include late onset, preservation of the lower limbs tendon reflexes, and slow progression. We describe clinical and electrophysiological features from three families with Friedreichlike phenotypes. Friedreich's ataxia diagnosis was confirmed by finding two allelic expansions of the GAA trinucleotide repeat at the X25 gene. In family 1 both patients had a late-onset phenotype with preservation of knee and ankle jerks, lack of cardiomyopathy, and preserved H reflex. One of them did not have electrophysiologic evidence of sensory axonal neuropathy. Patients from family 2 showed variability in the age of onset, and 2 out of 3 affected children had hyperactive lower limbs reflexes with preserved H reflex. Disease progression in a patient from family 3 was very slow after onset at the age of 21. The finding of two expanded alleles in these families confirms the wide variability of the clinical spectrum of Friedreich's ataxia. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1121–1126, 1997     

Unique origin and specific ethnic distribution of the Friedreich ataxia GAA expansion

The GAA triplet repeat expansion that causes Friedreich ataxia is found only in individuals of European, North African, Middle Eastern, or Indian origin (Indo-European and Afro-Asiatic speakers). Analysis of normal alleles of the GAA repeat and of closely linked markers suggests that expansions arose through a unique two-step process. A major implication of these findings is that Friedreich ataxia may not exist among sub-Saharan Africans, Amerindians, and people from China, Japan, and Southeast Asia.     

Friedreich ataxia in carriers of unstable borderline GAA triplet-repeat alleles

Friedreich ataxia patients are homozygous for expanded GAA triplet-repeats containing 66 to 1,700 triplets. We report two patients with delayed-onset, hyperreflexia and gradually progressive disease. Both were heterozygous for large expansions and also carried alleles with 44 and 66 triplet-repeats, respectively. Due to somatic instability, 15% (GAA-44) and 75% (GAA-66) of cells contained alleles with >/=66 triplet-repeats, constituting a plausible mechanism for their mild phenotype. A sibling with a stable GAA-37 allele and a large expansion was clinically normal. Instability of borderline alleles confers a risk for Friedreich ataxia, and the range of pathogenic alleles is broader than previously recognized.     

Oxidative stress in patients with Friedreich ataxia

Increased generation of reactive oxygen species may underlie the pathophysiology of Friedreich ataxia (FRDA). The authors measured concentrations of 8-hydroxy-2'-deoxyguanosine (8OH2'dG), a marker of oxidative DNA damage, in urine and of dihydroxybenzoic acid (DHBA), a marker of hydroxyl radical attack, in plasma of 33 patients with FRDA. They found a 2.6-fold increase in normalized urinary 8OH2'dG but no change in plasma DHBA as compared with controls. Oral treatment with 5 mg/kg/day of the antioxidant idebenone for 8 weeks significantly decreased urinary 8OH2'dG concentrations, indicating that 8OH2'dG may be useful in monitoring therapeutic interventions in patients with FRDA.-1721     

SARS-CoV-2 in patients with Friedreich ataxia

Journal of Neurology -     

Clinical experience with high-dose idebenone in Friedreich ataxia

Several reports in the literature describe the effects of low-dose (5 mg/kg/day) idebenone in significantly reducing cardiac hypertrophy in patients with Friedreich ataxia. However, the effects of idebenone on neurological function have not been reliably determined in these studies; when neurological parameters were reported, results were often inconclusive, usually because of subject heterogeneity and lack of adequate statistical power. In two of these studies, some patients showed beneficial effects of idebenone on their cardiomyopathy only when the dose was increased, prompting the systematic investigation of higher doses of idebenone. Following a phase 1 dose escalation study, a phase 2 tolerability and efficacy trial with low, intermediate, and high doses of idebenone was conducted. The results suggested that treatment with intermediate- and high-dose idebenone had beneficial effects on neurological symptoms. On the basis of these results, two phase 3 trials have been initiated, one in the United States with young ambulatory patients and one in Europe without limits on age and disease severity.     

Trinucleotide (GAA)n repeat expansion in two families with Friedreich's ataxia with retained reflexes

In occasional families in whom cases of classic Friedreich''s ataxia (FRDA) coexist with affected cases with retained reflexes, linkage analysis has shown that both map to the FRDA locus on chromosome 9q13-21.1. A gene X25 has been identified within the critical region of the FRDA locus, and an intronic expanded GAA trinucleotide repeat has been found in most cases of FRDA. We report two further FRDA families in whom some patients with classic FRDA were areflexic whereas others had brisk reflexes. Molecular genetic analysis disclosed an abnormal trinucleotide repeat expansion within intron 1 of the FRDA gene in both phenotypes.

     

Clinical experience with high-dose idebenone in Friedreich ataxia

Journal of Neurology - Several reports in the literature describe the effects of low-dose (5 mg/kg/day) idebenone in significantly reducing cardiac hypertrophy in patients with Friedreich ataxia....     

Predictors of progression in patients with Friedreich ataxia

Friedreich ataxia is an inherited, progressive, neurodegenerative disorder that is clinically heterogeneous. It is caused by a trinucleotide (GAA) repeat expansion resulting in frataxin loss and oxidative stress. We assessed clinical features including the development of cardiomyopathy and scoliosis and disease progression including loss of ambulation and interference with activities of daily living relative to the length of the GAA repeat, age of onset, and age of diagnosis in a retrospective cohort study of 61 genetically confirmed patients. The use of antioxidants such as vitamins, dietary supplements, and idebenone was also examined. Linear regression and Cox proportional hazard models assessed predictors to disease milestones. The shorter GAA allele accounted for part of the variability in the age of diagnosis (46%) and less in the age of onset (27%). Multivariate analysis demonstrated that age at diagnosis, which may incorporate other genetic and environmental factors, is more important than GAA length in predicting cardiomyopathy, scoliosis, and disease progression. © 2008 Movement Disorder Society     

The mismatch repair system protects against intergenerational GAA repeat instability in a Friedreich ataxia mouse model

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a dynamic GAA repeat expansion mutation within intron 1 of the FXN gene. Studies of mouse models for other trinucleotide repeat (TNR) disorders have revealed an important role of mismatch repair (MMR) proteins in TNR instability. To explore the potential role of MMR proteins on intergenerational GAA repeat instability in FRDA, we have analyzed the transmission of unstable GAA repeat expansions from FXN transgenic mice which have been crossed with mice that are deficient for Msh2, Msh3, Msh6 or Pms2. We find in all cases that absence of parental MMR protein not only maintains transmission of GAA expansions and contractions, but also increases GAA repeat mutability (expansions and/or contractions) in the offspring. This indicates that Msh2, Msh3, Msh6 and Pms2 proteins are not the cause of intergenerational GAA expansions or contractions, but act in their canonical MMR capacity to protect against GAA repeat instability. We further identified differential modes of action for the four MMR proteins. Thus, Msh2 and Msh3 protect against GAA repeat contractions, while Msh6 protects against both GAA repeat expansions and contractions, and Pms2 protects against GAA repeat expansions and also promotes contractions. Furthermore, we detected enhanced occupancy of Msh2 and Msh3 proteins downstream of the FXN expanded GAA repeat, suggesting a model in which Msh2/3 dimers are recruited to this region to repair mismatches that would otherwise produce intergenerational GAA contractions. These findings reveal substantial differences in the intergenerational dynamics of expanded GAA repeat sequences compared with expanded CAG/CTG repeats, where Msh2 and Msh3 are thought to actively promote repeat expansions.     

Clinical and genetic findings in Finnish ataxia patients with the spinocerebellar ataxia 8 repeat expansion

Spinocerebellar ataxia 8 (SCA8) is caused by a CTG repeat expansion in an untranslated region of a recently cloned gene on 13q21. The pathogenic role of this trinucleotide repeat was evaluated by examining 154 Finnish ataxia patients and 448 controls. Expansions ranging from 100 to 675 repeats were present in 9 (6%) unrelated patients and in 13 (3%) controls. There was a threefold excess of shorter expansions (<204 repeats) in the ataxia series, and the expansions tended to cluster in patients with a family history for the disease. Clinical and genetic data were subsequently collected from 15 patients. Common initial symptoms included gait instability, dysarthria, and tremor. A marked cerebellar atrophy in magnetic resonance imaging or computed tomography was found in all patients. Pyramidal affection was often seen, and various kinds of cognitive impairment were evident in 40% of patients. Disease progression was slow, and fluctuation of symptoms was commonly observed. A maternal penetrance bias was not seen, nor was there any clear-cut negative correlation between age of onset and repeat number. Meiotic but not mitotic instability of the repeat expansion was evident. Haplotype analysis suggests multiple origins for the Finnish spinocerebellar ataxia 8 repeat expansions.     

GAA repeat polymorphism in Turkish Friedreich's ataxia patients

Friedreich's ataxia (FRDA), the most common subtype of early onset hereditary spinocerebellar ataxia (SCA), is an autosomal recessive neurodegenerative disorder caused by unstable GAA tri-nucleotide expansions in the first intron of FRDA gene located at 9q13-q21.1 position. Results of GAA repeat polymorphism in 80 Turkish SCA patients and 38 family members of 11 typical FRDA patients were reported. GAA triplet repeat size ranged from approximately 7 to 34 in normal alleles and from approximately 66 to 1300 in mutant alleles. Twenty six patients were homozygous for GAA expansion and size of expanded alleles differed from approximately 425 to 1300 repeats. Children 2 and 6 years old (showing no ataxia symptoms) of one family had homozygous GAA expansions reaching approximately 925 repeats. All 11 families studied had at least 1 afflicted child and 9 parents and 2 siblings were carrier (heterozygous) with mutant alleles ranging from 66 to 850 repeats. Family studies confirmed the meiotic instability and stronger effect of expansion in the smaller alleles on phenotype and a negative correlation between GAA repeat expansion size and onset-age of the disease.     

Clinical and genetic correlate in childhood onset Friedreich ataxia.

We analyzed the clinical and genetic aspects of 28 FRDA patients from 20 families. 19 families were consanguineous. The onset was between 4 and 13 1/2 years of age (mean 15.4 +/- 6.2). Three patients presented with cardiomyopathy, one with weakness, and the rest with ataxia. There were two patients with preserved lower-limb deep tendon reflexes. Sensory nerve action potentials were reduced in 14/14 patients. Cardiac echograms were abnormal in 17/19 cases, and this was between 6 and 16 years of age (mean 10.1 +/- 3.5). Four families were multiplex. Clinical intra-familial variability was observed. Increased GAA repeats of the X25 gene were found in 27/28 patients studied, all in a homozygous state. 88.9% of patients had a smaller allele larger than 500 repeats, and 66.7% had more than 700 repeats. The patient who did not have increased GAA repeats in both alleles had peculiar findings. Significant correlation of expansion was obtained for the early onset, and cardiomyopathy as the onset.     

Cerebrospinal fluid concentrations of idebenone in Friedreich ataxia patients

We studied plasma and cerebrospinal fluid (CSF) concentrations of idebenone in five Friedreich ataxia patients on treatment with this antioxidant, and plasma and CSF ubiquinone-10 (Q (10)) concentrations in 15 controls. CSF idebenone concentrations were below the detection limit in 3 Friedreich ataxia patients and no association could be demonstrated between plasma and CSF idebenone values. Q (10) CSF concentrations (median: 2.25 nmol/L) were approximately 300 times lower than those of plasma (median: 0.77 micro mol/L). No correlation was observed between plasma and CSF Q (10) concentrations. A significantly positive correlation was observed between CSF total protein values (range 8.1 - 107.5 mg/dL; median: 29.5) and CSF Q (10) concentrations (Spearman test: r = 0.664; p = 0.01). Our findings suggest that less idebenone is distributed to the brain than to other tissues, although CSF does not appear to be an appropriate material for treatment monitoring of idebenone and other quinoid compounds.     

Frataxin gene point mutations in Italian Friedreich ataxia patients

Friedreich ataxia (FRDA) is associated with a GAA-trinucleotide-repeat expansion in the first intron of the FXN gene (9q13-21), which encodes a 210-amino-acid protein named frataxin. More than 95% of patients are homozygous for 90-1,300 repeat expansion on both alleles. The remaining patients have been shown to be compound heterozygous for a GAA expansion on one allele and a micromutation on the other. The reduction of both frataxin messenger RNA (mRNA) and protein was found to be proportional to the size of the smaller GAA repeat allele. We report a clinical and molecular study of 12 families in which classical FRDA patients were heterozygous for a GAA expansion on one allele. Sequence analysis of the FXN gene allowed the identification of the second disease-causing mutation in each heterozygous patient, which makes this the second largest series of FRDA compound heterozygotes reported thus far. We have identified seven mutations, four of which are novel. Five patients carried missense mutations, whereas eight patients carried null (frameshift or nonsense) mutations. Quantitation of frataxin levels in lymphoblastoid cell lines derived from six compound heterozygous patients showed a statistically significant correlation of residual protein levels with the age at onset (r = 0.82, p < 0.05) or the GAA expansion (r = -0.76, p < 0.1). In the group of patients heterozygous for a null allele, a strong (r = -0.94, p < 0.01) correlation was observed between the size of GAA expansion and the age at onset, thus lending support to the hypothesis that the residual function of frataxin in patients' cells derive exclusively from the expanded allele.