Progress in the treatment of Friedreich ataxia

Friedreich ataxia (FRDA) is a progressive neurological disorder affecting approximately 1 in 29,000 individuals of European descent. At present, there is no approved pharmacological treatment for this condition however research into treatment of FRDA has advanced considerably over the last two decades since the genetic cause was identified. Current proposed treatment strategies include decreasing oxidative stress, increasing cellular frataxin, improving mitochondrial function as well as modulating frataxin controlled metabolic pathways. Genetic and cell based therapies also hold great promise. Finally, physical therapies are being explored as a means of maximising function in those affected by FRDA.     

Pathophysiogical and therapeutic progress in Friedreich ataxia

Friedreich ataxia (FRDA) is the most common hereditary autosomal recessive ataxia, but is also a multisystemic condition with frequent presence of cardiomyopathy or diabetes. It has been linked to expansion of a GAA-triplet repeat in the first intron of the FXN gene, leading to a reduced level of frataxin, a mitochondrial protein which, by controlling both iron entry and/or sulfide production, is essential to properly assemble and protect the Fe-S cluster during the initial stage of biogenesis. Several data emphasize the role of oxidative damage in FRDA, but better understanding of pathophysiological consequences of FXN mutations has led to develop animal models. Conditional knockout models recapitulate important features of the human disease but lack the genetic context, GAA repeat expansion-based knock-in and transgenic models carry a GAA repeat expansion but they only show a very mild phenotype. Cells derived from FRDA patients constitute the most relevant frataxin-deficient cell model as they carry the complete frataxin locus together with GAA repeat expansions and regulatory sequences. Induced pluripotent stem cell (iPSC)-derived neurons present a maturation delay and lower mitochondrial membrane potential, while cardiomyocytes exhibit progressive mitochondrial degeneration, with frequent dark mitochondria and proliferation/accumulation of normal mitochondria. Efforts in developing therapeutic strategies can be divided into three categories: iron chelators, antioxidants and/or stimulants of mitochondrial biogenesis, and frataxin level modifiers. A promising therapeutic strategy that is currently the subject of intense research is to directly target the heterochromatin state of the GAA repeat expansion with histone deacytelase inhibitors (HDACi) to restore frataxin levels.     

Locus heterogeneity in Friedreich ataxia

Friedreich ataxia (FRDA) is the most common form of autosomal recessive ataxia. The disease locus was assigned to chromosome 9 and the disease gene, STM7/X25, has been isolated. To date most data suggest locus homogeneity in FRDA. We now provide strong evidence of a second FRDA locus. Studying two siblings with FRDA from two families we did not detect a mutation in STM7/X25. Haplotype analysis of the STM7/X25 region of chromosome 9 demonstrated that the relevant portion of chromosome 9 differs in the patients. Although the patients studied had typical FRDA, one sibpair had the uncommon symptom of retained tendon reflexes. In order to investigate whether retained tendon reflexes are characteristic of FRDA caused by the second locus, FRDA2, we studied an unrelated FRDA patient with retained tendon reflexes. The observation of typical mutations in STM7/X25 (GAA exopansions) in this patient demonstrates that the two genetically different forms of FRDA cannot be distinguished clinically. Received December 19, 1996; Revised and Accepted January 22, 1997     

A case of successful pregnancy in a woman with Friedreich ataxia

We report on a 34-year-old woman with advanced FA who achieved a successful pregnancy. The neurological and cardiological features of the disease remained unchanged during and after pregnancy. Because of a slight respiratory impairment, which appeared at the 6th month, cesarean section was performed at the 34th week. FA is not necessarily a bar to successful pregnancy, but early referral to a cardiologist and respiratory monitoring is mandatory. The risk of transmission of the disease for our couple was 1/95.5 compared with 1/36.000 for a non-affected couple.

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Sommario Descriviamo il caso di una donna di 34 anni affetta da Atassia di Friedreich che ha condotto con successo una gravidanza. La sintomatologia neurologica e cardiologica non ha subito variazioni nel corso della gravidanza, mentre un modesto deficit respiratorio ha condotto a terminare la gravidanza con taglio cesareo alla 34.ma settimana. Con il supporto di uno stretto monitoraggio cardiaco e respiratorio, l'Atassia di Friedreich non è necessariamente una controindicazione alla gravidanza. Il rischio di trasmissione della malattia per la nostra coppia era di 1/95.5 contro 1/36.000 per una coppia di non affetti.

     

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     

Ataxia clinical rating scale in Friedreich disease

The Ataxia Clinical Rating Scale was used on 22 patients with Friedreich disease. We found a positive correlation (r=0.64, p<0.005) between total score and duration of symptoms. For this reason the scale may be useful in the follow-up of patients affected by Friedreich disease.

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Sommario La Ataxia Clinical Rating Scale è stata applicata a 22 pazienti affetti da malattia di Friedreich. Abbiamo riscontrato una correlazione positiva (r=0.64, p<0.005) tra il punteggio totale e la durata della sintomatologia. Per questo motivo la scala è utile nel follow-up dei pazienti affetti da malattia di Friedreich.

     

Brainstem auditory-evoked responses and clinical picture in a one year follow-up of 18 patients with Friedreich ataxia

Brainstem auditory-evoked responses (BAER) and behavior audiometry were evaluated on 18 patients with Friedreich ataxia. Behavior audiometry showed a normal pure tone test, normal performance intensity and phonetically balanced functions in all patients. BAER were abnormal in all patients. The data obtained show a good correlation between BAER and clinical picture and suggest that BAER could be useful in monitoring the clinical condition of FA patients.

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Sommario In 18 pazienti con atassia spinocerebellare di Friedreich sono stati valutati i potenziali evocati acustici del tronco (PEAT) e le audiometrie comportamentale. L'audiometria comportamentale ha dimostrato in tutti i pazienti: a) normale test audiometrico tonale liminare; b) normale risposta per la intensità di stimolo usata; c) normale risposta al test delle parole foneticamente bilanciate. I PEAT sono risultati peraltro anormali in tutti i pazienti. I dati ottenuti sono in favore di una correlazione positiva tra stadio clinico della malattia e grado di alterazione dei PEAT, suggerendo che i PEAT possono essere utilizzati nel monitoraggio della condizione clinica dei pazienti con atassia di Friedreich.

     

Quality of life in Friedreich ataxia: what clinical,social and demographic factors are important?

The aim of this study was to examine the impact of Friedreich ataxia (FRDA) on quality of life (QOL) using a generic tool to explore factors potentially associated with health status. Sixty-three individuals with genetically confirmed FRDA, self completed the Medical Outcomes Study 36 item Short Form Health Survey Version 2 (SF-36V2) and were assessed using the FRDA Rating Scale. Disease-specific, demographic, and social characteristics were also recorded. SF-36V2 results were compared with Australian population norms. Sample subgroups of disease severity and age at disease onset were reviewed. Physical and mental component summaries were examined in relation to clinical and social characteristics using multiple linear regression. QOL is significantly worse in individuals with FRDA compared with population norms. Those with severe disease did not perceive a lower QOL than those with mild or moderate disease except in their physical functioning. A later age of onset and increased disease severity were negatively associated with physical QOL, whilst, increased disease duration was positively associated with mental QOL. There were limitations associated with the use of SF-36V2 in the FRDA population. Further exploration of health-related QOL and FRDA may benefit from the use of a more appropriate generic tool.     

Cerebral compensation during motor function in Friedreich ataxia: The IMAGE‐FRDA study

Background : Friedreich ataxia is characterized by progressive motor incoordination that is linked to peripheral, spinal, and cerebellar neuropathology. Cerebral abnormalities are also reported in Friedreich ataxia, but their role in disease expression remains unclear. Methods : In this cross‐sectional functional magnetic resonance imaging study, 25 individuals with Friedreich ataxia and 33 healthy controls performed simple (self‐paced single‐finger) and complex (visually cued multifinger) tapping tasks to respectively gauge basic and attentionally demanding motor behavior. For each task, whole brain functional activations were compared between groups and correlated with disease severity and offline measures of motor dexterity. Results : During simple finger tapping, cerebral hyperactivation in individuals with Friedreich ataxia at the lower end of clinical severity and cerebral hypoactivation in those more severely affected was observed in premotor/ventral attention brain regions, including the supplementary motor area and anterior insula. Greater activation in this network correlated with greater offline finger tapping precision. Complex, attentionally demanding finger tapping was also associated with cerebral hyperactivation, but in this case within dorsolateral prefrontal regions of the executive control network and superior parietal regions of the dorsal attention system. Greater offline motor precision was associated with less activation in the dorsal attention network. Discussion : Compensatory activity is evident in the cerebral cortex in individuals with Friedreich ataxia. Early compensation followed by later decline in premotor/ventral attention systems demonstrates capacity‐limited neural reserve, while the additional engagement of higher order brain networks is indicative of compensatory task strategies. Network‐level changes in cerebral brain function thus potentially serve to mitigate the impact of motor impairments in Friedreich ataxia. © 2017 International Parkinson and Movement Disorder Society     

Pyruvate-dehydrogenase complex in ataxic patients: Enzyme deficiency in ataxic encephalopathy plus lactic acidosis and normal activity in Friedreich ataxia

Pyruvate dehydrogenase complex (PDHC) activity was measured in cultured fibroblasts from 12 patients with Friedreich's ataxia (FA), and in 1 patient with lactic acidosis and ataxia. The activities obtained after extraction of PDHC by different methods were compared. Triton-X-100 extraction yielded enzyme activities 5 to 10 times greater than those obtained with the older methods. With this sensitive technique, PDHC activity was markedly deficient in fibroblasts from the patient with lactic acidosis and ataxia but it was normal in the fibroblasts from FA patients. Mg ⁺⁺ activation of the PDHC in FA fibroblasts was normal.

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Sommario Il complesso enzimatico piruvico-deidrogenasi (PDHC) è stato misurato in fibroblasti coltivati da 12 pazienti con atassia di Friedreich ed 1 paziente con acidosi lattica e atassia. Le attività enzimatiche ottenute con diversi metodi di estrazione del PDHC sono stati confrontati. La estrazione con Triton-X-100 permetteva di ottenere attività enzimatiche da 5 a 10 volte più elevate di quelle ottenute con i metodi precedenti. Con questo sensibile metodo l'attività PDHC era molto ridotta nei fibroblasti del paziente con acidosi lattica e atassia: l'attività era invece normale nei fibroblasti dei pazienti con atassia di Friedreich. La attivazione del PDHC nei fibroblasti dei pazienti con Friedreich era normale.

     

Comparison of three clinical rating scales in Friedreich ataxia (FRDA)

To test the validity and reliability of the scale for the assessment and rating of ataxia (SARA) in Friedreich ataxia (FRDA). SARA is limited to eight items and can be performed rapidly. Ninety‐six patients with a molecular genetic diagnosis of FRDA were rated using three different clinical scales, the FRDA Rating Scale (FARS), the International Cooperative Ataxia Rating Scale (ICARS), and SARA. Despite considerable discrepancies in scale size and subscale structure, SARA total scores were significantly correlated with ICARS (r = 0.953, P < 0.0001) and FARS (r = 0.938, P < 0.0001) total scores. SARA total scores also correlated with the activities of daily living (ADL, r = 0.929, P < 0.0001). Although originally developed for the use in dominantly inherited ataxias, which are primarily ataxias of the cerebellar type, SARA can also be used successfully to assess afferent ataxia, which is the predominant form in FRDA. Because SARA is characterized by high interrater reliability and practicability, SARA is applicable and well suited forclinical trials of FRDA. © 2009 Movement Disorder Society     

Restless legs syndrome in Friedreich ataxia: A polysomnographic study

Friedreich ataxia (FA) is the most common type of hereditary ataxia. Frataxin deficiency due to a GAA expansion in the first intron of chromosome 9 results in intramitochondrial iron accumulation. On the basis of the patients' complaints about sleep disturbance and pathophysiological considerations, we systematically assessed sleep history and polysomnography in FA. We included 16 consecutive FA patients (11 men, 5 women; mean age, 35.4 ± 11.1 years) with a mean disease duration of 16.5 ± 7.0 years. All patients underwent a standardized protocol including a detailed sleep history and polysomnographic recordings. Eight out of 16 patients were diagnosed with restless legs syndrome (RLS). In seven patients, RLS onset was after the onset of FA. Interestingly, FA patients with RLS had significantly lower serum ferritin levels than FA patients without RLS (76.3 ± 56.0 μg/L vs. 176.3 ± 100.7 μg/L; P = 0.043 after correction for sex and age). Moreover, periodic leg movements in wakefulness (PLMW) indices were significantly higher in FA patients with RLS than FA patients without RLS (FA with RLS, 118.1 ± 50.7; FA without RLS, 65.6 ± 44.2; P = 0.028). There was an inverse correlation between serum ferritin levels and PLMW indices obtained in all FA patients (rho ?0.538, P = 0.039). RLS is common in FA. Its frequency in this primarily spinal ataxia appears consistent with the concept of dysfunctional spinal sensorimotor integration in the pathophysiology of RLS. The finding that RLS is more frequent in the context of lower serum ferritin levels in FA is interesting, but requires further investigation in larger patient samples. © 2009 Movement Disorder Society.     

Atypical Friedreich ataxia in patients with FXN p.R165P point mutation or comorbid hemochromatosis

BackgroundCompound heterozygosity for a trinucleotide repeat expansion and a point mutation in the FXN gene is a rare cause of Friedreich ataxia (FRDA).MethodsWe identified three Swedish FRDA patients with an FXN p.R165P missense mutation and compared their clinical features with six homozygote trinucleotide repeat expansion carriers. Patients were assessed clinically. Trinucleotide expansion length was determined and lymphocyte frataxin levels measured.Resultsp.R165P mutation carriers became wheelchair bound early, but had retained reflexes, better arm function, milder dysarthria, and were more independent in activities of daily living. One p.R165P mutation carrier developed psychosis. Frataxin levels were higher than in homozygous trinucleotide expansion patients. One patient with homozygous trinucleotide repeat expansions and comorbid hemochromatosis had more severe FRDA symptoms than his sibling without hemochromatosis.Conclusionp.R165P patients progress to a less disabling disease state than typical FRDA. Comorbid hemochromatosis may worsen FRDA symptoms through additive effects on iron metabolism.     

The correlation of clinical phenotype in Friedreich ataxia with the site of point mutations in the FRDA gene

Most cases of Friedreich ataxia (FRDA) are due to expansions of a GAA trinucleotide repeat sequence in the FRDA gene coding for frataxin, a protein of poorly understood function which may regulate mitochondrial iron transport. However, between 1% and 5% of mutations are single base changes in the sequence of the FRDA gene, causing missense, nonsense, or splicing mutations. We describe three new mutations, IVS4nt2 (T to G), R165C , and L182F , which occur in patients in association with GAA expansions. These cases, and a further five reported cases of point mutations causing FRDA, demonstrate that splicing, nonsense, or initiation codon mutations (which cause a complete absence of functional frataxin) are associated with a severe phenotype. Missense mutations, even in highly evolutionally conserved amino acids, may cause a mild or severe phenotype. Received: March 24, 1998 / Accepted: May 28, 1998