Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The clinical and genetic features of 80 patients with Friedreich's disease from 64 families are described. Diagnostic criteria were: no evidence of dominant inheritance, onset by the age of 20 years, progressive unremitting ataxia of limbs and gait, and absence of knee and ankle jerks. Furthermore, at least one of the following accessory signs was present: dysarthria, extensor plantar response and echocardiographic evidence of hypertrophic cardiomyopathy. Two peaks of onset age were evident at 6-9 and 12-15 years. Analysis of intra-family variation of onset age and absence of clustering of cardiomyopathy and diabetes did not suggest genetic heterogeneity. Peripheral nerve impairment was an early finding and showed slight further progression, whereas involvement of the cerebellar and corticospinal pathways appeared later and mainly accounted for the progressive worsening of the disease.
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PMID:Genetic data and natural history of Friedreich's disease: a study of 80 Italian patients. 227 67

Phase three of the Quebec Cooperative Study of Friedreich's Ataxia was devoted to an understanding of the physiopathology of individual symptoms on the basis of previously discovered biochemical leads. The present paper attempts to pull these results together by presenting, as a hypothesis, a unifying scheme of possible interactions and relationships. The central core of this hypothesis is the demonstration in Friedreich's ataxia of a state of mitochondrial energy deprivation. This is indirectly responsible for such associated and important symptoms as muscle weakness, dying-back neuropathy, scoliosis and hypertrophic cardiomyopathy. Secondarily, and possibly as an independent but linked-event, the entry of glucose into cells and pyruvate oxidation, are slowed down, favoring the development of diabetes. As a consequence, tissue concentrations of glutamic acid and aspartic acid are decreased, particularly in more vulnerable areas such as the cerebellum, brain stem and dorsal root ganglia. This tissue deficiency in putative excitatory neurotransmitters is directly responsible for the symptom of ataxia. This conclusion is reinforced by the correction of the ataxia in experimental animals, by the intraventricular injection of the same amino acids, and not by the injection of other stimulants of motricity. The observed mitochondrial energy deprivation could be the metabolic consequence of major changes in the linoleic acid (18.2) composition of inner mitochondrial membrane phospholipids, such as cardiolipin. Such decreases in membrane 18:2 could be the result of interference with the normal incorporation of this fatty acid to lipoproteins and/or cell membranes. It is at this level that the search for the specific enzyme defect in Friedreich's ataxia is continuing.
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PMID:Friedreich's ataxia 1980. An overview of the physiopathology. 678 90

Mutation of mitochondrial (mt) DNA at nucleotide (nt) 8993 has been reported to cause neurogenic weakness, ataxia, retinitis pigmentosa (NARP), or Leigh syndrome (LS). We report a family in whom the mutation was expressed clinically as LS and hypertrophic cardiomyopathy (CMP) in a boy who presented with a history of developmental delay and hypotonia, and who had recurrent lactic acidosis. The mother's first pregnancy resulted in the birth of a stillborn female; an apparently healthy older brother had died suddenly (SIDS) at age 2 months. MtDNA analysis identified the presence of the T8993G point mutation, which was found to be heteroplasmic in the patient's skeletal muscle (90%) and fibroblasts (90%). The identical mutation was present in leukocytes (38%) isolated from the mother, but not from the father or maternal grandmother. Our findings expand the clinical phenotype of the nt 8993 mtDNA mutation to include hypertrophic cardiomyopathy and confirm its cause of LS.
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PMID:Leigh syndrome and hypertrophic cardiomyopathy in an infant with a mitochondrial DNA point mutation (T8993G). 804 71

The onset of Friedreich ataxia (FA) was before 10 years of age in 36 out of 95 personally observed patients. We studied the clinical and laboratory findings of these childhood onset patients. Mean onset age +/- SD was 6.3 +/- 2.4 years. Gait and stance ataxia and lower limb areflexia were constant, dysmetria, dysarthria, Babinski sign, pes cavus, scoliosis and decreased vibration sense were present in the majority of patients. Higher occurrence of diabetes in childhood onset cases (25%) was the only statistical difference in comparison with later onset patients. Mean onset age of diabetes was 21.1 +/- 6.9 years and all patients required insulin. ECG was abnormal in 72% of the patients and echocardiographic evidence of hypertrophic cardiomyopathy was found in 43%. Linkage analysis, performed in 10 families, showed no recombination between the polymorphic markers of the 9q13-21.1 region and the disease locus with a peak lod score of 4.21 at a recombination fraction = 0.00.
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PMID:Childhood onset of Friedreich ataxia: a clinical and genetic study of 36 cases. 867 22

A new autosomal dominant syndrome in a Swedish pedigree is described. Five patients were affected with cerebellar ataxia and sensorineural deafness. Four of these patients had symptoms of narcolepsy. Optic atrophy, other neurological abnormalities and psychiatric symptoms developed with increasing disease duration. Three patients had non-neurological disease in addition, including diabetes mellitus in two and hypertrophic cardiomyopathy in one. Autopsy with neuropathological examination was performed in one case. Molecular studies focused on the short arm of chromosome 6, including the HLA DR2 locus associated with narcolepsy and the (CAG)n repeat at the spinocerebellar ataxia type 1 (SCA1) locus. Biochemical investigation of muscle biopsy of one case indicated mitochondrial dysfunction with selective decrease in ATP production for substrates that normally give the highest rates. The activity of glutamate dehydrogenase was reduced, indicating a low mitochondrial density. We postulate an autosomal dominant genetic factor responsible for this syndrome. Linkage was excluded to HLA DR2, and a normal sized SCA1 repeat was observed. We conclude that a locus predisposing to ataxia, deafness and narcolepsy exists outside this region of chromosome 6.
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PMID:Autosomal dominant cerebellar ataxia deafness and narcolepsy. 874 54

Friedreich ataxia (FRDA) is a common autosomal recessive degenerative disease (1/50,000 live births) characterized by a progressive-gait and limb ataxia with lack of tendon reflexes in the legs, dysarthria and pyramidal weakness of the inferior limbs. Hypertrophic cardiomyopathy is observed in most FRDA patients. The gene associated with the disease has been mapped to chromosome 9q13 (ref. 3) and encodes a 210-amino-acid protein, frataxin. FRDA is caused primarily by a GAA repeat expansion within the first intron of the frataxin gene, which accounts for 98% of mutant alleles. The function of the protein is unknown, but an increased iron content has been reported in hearts of FRDA patients and in mitochondria of yeast strains carrying a deleted frataxin gene counterpart (YFH1), suggesting that frataxin plays a major role in regulating mitochondrial iron transport. Here, we report a deficient activity of the iron-sulphur (Fe-S) cluster-containing subunits of mitochondrial respiratory complexes I, II and III in the endomyocardial biopsy of two unrelated FRDA patients. Aconitase, an iron-sulphur protein involved in iron homeostasis, was found to be deficient as well. Moreover, disruption of the YFH1 gene resulted in multiple Fe-S-dependent enzyme deficiencies in yeast. The deficiency of Fe-S-dependent enzyme activities in both FRDA patients and yeast should be related to mitochondrial iron accumulation, especially as Fe-S proteins are remarkably sensitive to free radicals. Mutated frataxin triggers aconitase and mitochondrial Fe-S respiratory enzyme deficiency in FRDA, which should therefore be regarded as a mitochondrial disorder.
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PMID:Aconitase and mitochondrial iron-sulphur protein deficiency in Friedreich ataxia. 932 46

Friedreich's ataxia is an autosomal recessively inherited neurodegenerative disorder caused by expansions of an unstable GAA trinucleotide repeat in the STM7/X25 gene on chromosome 9q. We studied the (GAA)n polymorphism in 178 healthy controls and 102 patients with idiopathic ataxia. The repeat size ranged from 7 to 29 (GAA)n motifs on normal chromosomes and from 66 to 1360 trinucleotide repetitions in Friedreich's ataxia patients. Meiotic instability of expanded alleles was observed without significant differences in maternal and paternal transmissions. Thirty-six of 102 patients were typed homozygous for expanded (GAA)n alleles. Twenty-seven of these presented with the typical Friedreich's ataxia symptoms and nine patients with an atypical Friedreich's ataxia phenotype. Before molecular genetic diagnosis had been performed seven of these patients had been classified as early onset cerebellar ataxia and two as idiopathic sporadic cerebellar ataxia of late onset. In contrast, in one family with typical Friedreich's ataxia phenotype we did not find an expanded allele; this suggests that there can be either point mutations in the X25 gene on both chromosomes or locus heterogeneity in Friedreich's ataxia. The phenotypic spectrum of Friedreich's ataxia is much broader than considered before. Early onset, areflexia, extensor plantar responses and reduced vibration sense should no longer be considered essential diagnostic criteria of Friedreich's ataxia. In comparison with the non-Friedreich's ataxia group hypertrophic cardiomyopathy seems to be the only symptom specific for Friedreich's ataxia. However, it is not obligatory. The phenotype is significantly influenced by the number of GAA repeats with close genotype-phenotype relationships when the smaller of the two alleles is considered. Repeat length correlated inversely with age at onset, onset of dysarthria and progression rate. In conclusion, molecular genetic analysis appears mandatory for the diagnosis and genetic counselling of Friedreich's ataxia. The molecular genetic test should be applied not only to patients with typical Friedreich's ataxia phenotype but also in all cases of idiopathic autosomal recessive or sporadic ataxia.
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PMID:Friedreich's ataxia. Revision of the phenotype according to molecular genetics. 944 68

Mitochondrial diseases are characterized by considerable clinical variability and are most often caused by mutations in mtDNA. Because of the phenotypic variability, epidemiological studies of the frequency of these disorders have been difficult to perform. We studied the prevalence of the mtDNA mutation at nucleotide 3243 in an adult population of 245,201 individuals. This mutation is the most common molecular etiology of MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes), one of the clinical entities among the mitochondrial disorders. Patients with diabetes mellitus, sensorineural hearing impairment, epilepsy, occipital brain infarct, ophthalmoplegia, cerebral white-matter disease, basal-ganglia calcifications, hypertrophic cardiomyopathy, or ataxia were ascertained on the basis of defined clinical criteria and family-history data. A total of 615 patients were identified, and 480 samples were examined for the mutation. The mutation was found in 11 pedigrees, and its frequency was calculated to be >=16. 3/100,000 in the adult population (95% confidence interval 11.3-21. 4/100,000). The mutation had arisen in the population at least nine times, as determined by mtDNA haplotyping. Clinical evaluation of the probands revealed a syndrome that most frequently consisted of hearing impairment, cognitive decline, and short stature. The high prevalence of the common MELAS mutation in the adult population suggests that mitochondrial disorders constitute one of the largest diagnostic categories of neurogenetic diseases.
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PMID:Epidemiology of A3243G, the mutation for mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes: prevalence of the mutation in an adult population. 968 91

Friedreich's ataxia, the most common autosomal recessive inherited ataxia, is characterized by progressive gait and limb ataxia. Friedreich's ataxia is known for its occurrence within the first or second decade of life and is associated with hypertrophic cardiomyopathy, and in some cases with diabetes. Genetically, it is identified by the expression of an unstable trinucleotide GAA repeat expansion located in the first intron of the X25 gene on chromosome 9. Two brothers with very late adult-onset ataxia, and their unaffected sister, were examined for the clinical presentation of FA and for the presence of the mutated FA gene. The relationship of the expanded gene sequence to the severity of disease and age of onset were evaluated. Clinical examination revealed that the two brothers had mild ataxia and proprioceptive loss, with age of onset between 60 and 70 years of age. DNA from peripheral blood nucleated cells demonstrated a small homozygous expansion, with approximately 120-130 GAA repeats in the X25 gene in both patients. The expanded repeats were interrupted either with GAAGAG, GAAGGA, or GAAGAAAA sequences. The unaffected sister carried a normal FA genotype with 8-uninterrupted GAA repeat, observed by sequence analysis. In addition, the levels of FA gene transcript in both brothers were relatively lower than that in the unaffected sister. No detectable cardiomyopathy or diabetes was observed. Phenotypic diversity of FA is increasingly expanding. The age of onset and the structure of GAA repeat expansion plays an important role in determining the clinical features and the differential diagnosis of FA. The confirmation of the FA gene mutation in the atypical case, broadens the clinical spectrum of FA, and supports the idea that patients with even a mild form of ataxia of late adult onset should be considered for molecular testing.
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PMID:Sequence variation in GAA repeat expansions may cause differential phenotype display in Friedreich's ataxia. 1174 52

Friedreich's ataxia (FRDA) is a neuro-degenerative disease causing limb and gait ataxia and hypertrophic cardiomyopathy. It results from a triplet expansion in the first intron of the frataxin gene encoding a mitochondrial protein of yet unknown function. Cells with low frataxin content display generalized deficiency of mitochondrial iron-sulfur cluster-containing proteins, which presumably denotes overproduction of superoxide radicals in these organelles. Idebenone, a short-chain quinone, may act as a potent free radical scavenger protecting mitochondria against oxidative stress. We therefore carried out an open trial of idebenone (oral supplementation; 5mg/kg/day) in a large series of FRDA patients and followed their left ventricular mass and function. Consistent and definitive worsening being observed in the natural course of the disease and cardiac hypertrophy having no chance of spontaneous reversal and to be subject to a placebo effect, the patient's heart status before and after the treatment was used to unambiguously establish the effect of the drug. After six months, heart ultrasound revealed more than 20% reduction of left ventricular mass in about half of the patients (p < 0.001) and no significant change in the other half. Since any measurable reversion of this pathogenic trait is highly significant, this demonstrates the efficiency of idebenone in controlling heart hypertrophy in FRDA. Owing to the absence of side effects of the drug, idebenone (up to 15mg/kg/day) should be prescribed for FRDA patients continuously as early as possible.
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PMID:Heart hypertrophy and function are improved by idebenone in Friedreich's ataxia. 1206 12


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