[Show abstract][Hide abstract] ABSTRACT: Neuroferritinopathy is a progressive potentially treatable adult-onset movement disorder caused by mutations in the ferritin light chain gene (FTL1). Features overlap with common extrapyramidal disorders: idiopathic torsion dystonia, idiopathic Parkinson's disease and Huntington's disease, but the phenotype and natural history have not been defined. We studied a genetically homogeneous group of 41 subjects with the 460InsA mutation in FTL1, documenting the presentation, clinical course, biochemistry and neuroimaging. The mean age of onset was 39.4 years (SD = 13.3, range 13-63), beginning with chorea in 50%, focal lower limb dystonia in 42.5% and parkinsonism in 7.5%. The majority reported a family history of a movement disorder often misdiagnosed as Huntington's disease. The disease progressed relentlessly, becoming generalized over a 5-10 year period, eventually leading to aphonia, dysphagia and severe motor disability with subcortical/frontal cognitive dysfunction as a late feature. A characteristic action-specific facial dystonia was common (65%), and in 63% there was asymmetry throughout the disease course. Serum ferritin levels were low in the majority of males and post-menopausal females, but within normal limits for pre-menopausal females. MR brain imaging was abnormal on all affected individuals and one presymptomatic carrier. In conclusion, isolated parkinsonism is unusual in neuroferritinopathy, and unlike Huntington's disease, cognitive changes are absent or subtle in the early stages. Depressed serum ferritin is common and provides a useful screening test in routine practice, and gradient echo brain MRI will identify all symptomatic cases.
[Show abstract][Hide abstract] ABSTRACT: Whereas the majority of disease-related mitochondrial DNA mutations exhibit significant biochemical and clinical heterogeneity, mutations within the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle and a clinical presentation involving exercise intolerance. Recent studies have shown that a small number of MTCYB mutations are associated with a combined enzyme complex defect involving both complexes I and III, on account of the fact that an absence of assembled complex III results in a dramatic loss of complex I, confirming a structural dependence between these two complexes. We present the biochemical and molecular genetic studies of a patient with both muscle and brain involvement and a severe reduction in the activities of both complexes I and III in skeletal muscle due to a novel mutation in the MTCYB gene that predicts the substitution (Arg318Pro) of a highly conserved amino acid. Consistent with the dramatic biochemical defect, Western blotting and BN-PAGE experiments demonstrated loss of assembled complex I and III subunits. Biochemical studies of the equivalent amino-acid substitution (Lys319Pro) in the yeast enzyme showed a loss of enzyme activity and decrease in the steady-state level of bc1 complex in the mutant confirming pathogenicity.
[Show abstract][Hide abstract] ABSTRACT: Neuroferritinopathy is a recently recognized, dominantly inherited movement disorder caused by a mutation of the ferritin light chain gene. We present video case reports of 4 individuals with neuroferritinopathy chosen to illustrate how this disorder can present and subsequently progress clinically. The clinical phenotype of this disorder is highly variable with symptoms beginning in the third to sixth decades. Chorea, dystonia, or an akinetic-rigid syndrome can predominate in different individuals. Neuroferritinopathy is not restricted to the UK and it has been described in apparently sporadic cases. The diagnosis should therefore be considered in patients with a wide variety of different movement disorders. Characteristic neuroimaging assists in identifying affected individuals.
Movement Disorders 01/2005; 20(1):95-9. DOI:10.1002/mds.20284 · 5.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe a young woman with a progressive mitochondrial myopathy that started with muscle weakness and went on to include deafness, dementia and ataxia. Skeletal muscle showed the histological and biochemical features of mitochondrial respiratory chain dysfunction. Genetic analysis identified a novel, heteroplasmic, A to G transition in tRNA(Ser(UCN)) at position 7480 affecting a highly conserved base in the anticodon loop. Single-fibre PCR showed highest levels of mutation in cytochrome c-oxidase-deficient fibres and quantification in two biopsies taken 5 years apart showed no change in percentage heteroplasmy. The mutation was present at lower levels in the patient's blood, but was not found in either her mother's or sister's blood and skeletal muscle, suggesting a sporadic occurrence. This is the eighth disease-causing mutation in this tRNA gene and confirms serine (UCN) as one of the most common sites for mtDNA mutation.
[Show abstract][Hide abstract] ABSTRACT: Neuroferritinopathy is a recently recognised genetic disease resulting in a dominantly inherited movement disorder. The condition was mapped by linkage analysis to chromosome 19q13.3 and found to be due to a single adenine insertion in the ferritin light chain (FTL) gene at position 460-461 which is predicted to alter the C terminus of the FTL polypeptide. Clinical features of neuroferritinopathy are highly variable, with chorea, dystonia, and Parkinsonian features predominating in different affected individuals. The most consistent feature is a dystonic dysarthria. Symptoms and abnormal physical signs appear to be restricted to the nervous system and onset is typically in the fourth to sixth decades. Low serum ferritin also characterises this condition. Brain MR imaging of affected patients demonstrates iron deposition in the basal ganglia, progressing over years to cystic degeneration, and brain histochemistry shows abnormal aggregates of ferritin and iron. Now that the molecular basis of the condition is known, therapeutic interventions to reduce or reverse brain iron deposition are being evaluated. This rare disease provides evidence of a central role for iron metabolism in neurodegenerative disorders.
[Show abstract][Hide abstract] ABSTRACT: We describe here a previously unknown, dominantly inherited, late-onset basal ganglia disease, variably presenting with extrapyramidal features similar to those of Huntington's disease (HD) or parkinsonism. We mapped the disorder, by linkage analysis, to 19q13.3, which contains the gene for ferritin light polypeptide (FTL). We found an adenine insertion at position 460-461 that is predicted to alter carboxy-terminal residues of the gene product. Brain histochemistry disclosed abnormal aggregates of ferritin and iron. Low serum ferritin levels also characterized patients. Ferritin, the main iron storage protein, is composed of 24 subunits of two types (heavy, H and light, L) which form a soluble, hollow sphere. Brain iron deposition increases normally with age, especially in the basal ganglia, and is a suspected causative factor in several neurodegenerative diseases in which it correlates with visible pathology, possibly by its involvement in toxic free-radical reactions. We found the same mutation in five apparently unrelated subjects with similar extrapyramidal symptoms. An abnormality in ferritin strongly indicates a primary function for iron in the pathogenesis of this new disease, for which we propose the name 'neuroferritinopathy'.
[Show abstract][Hide abstract] ABSTRACT: We report a new mutation, a G to A transition at nucleotide position 4298 within the mitochondrial tRNA(Ile) gene in a patient with chronic progressive external ophthalmoplegia and multiple sclerosis. The mutation, which alters an evolutionary conserved nucleotide within the anticodon stem, was heteroplasmic in skeletal muscle but was not present in the patient's blood. Single fibre PCR analysis revealed significantly higher levels of the G4298A mutation in cytochrome c oxidase (COX) negative fibres than in COX-positive fibres. This mutation represents the seventh pathogenic nucleotide substitution to be found in this gene and as such confirms the tRNA(Ile) gene as a susceptible "hot spot" for mitochondrial DNA point mutations. Of particular interest is that this patient has the clinical features of both multiple sclerosis and a mitochondrial DNA disorder.
Biochemical and Biophysical Research Communications 03/1998; 243(1):47-51. DOI:10.1006/bbrc.1997.8055 · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Defects of the mitochondrial respiratory chain are increasingly being recognized as an important cause of neurological disease in humans. In many of these patients, the biochemical defect results from an abnormality of the mitochondrial genome. Respiratory chain defects involving complex II, which is entirely encoded by the nuclear genome, are comparatively rare. We report the clinical and biochemical findings in 2 elderly sisters who presented with late-onset neurodegenerative disease. In both patients, a partial deficiency of complex II (approximately 50% of control values) was shown to be present in mitochondria from muscle and platelets. The enzyme defect was not expressed in cultured skin fibroblasts or immortalized lymphocytes. There was an overexpression of the 70-kd flavoprotein subunit in muscle mitochondria from both patients, although we showed that this subunit is present in normal amounts in mitochondrial membranes. Our studies highlight the diversity of the clinical presentation of respiratory chain disease and that complex II deficiency should enter the differential diagnosis of certain patients with late-onset neurodegenerative disease.
Annals of Neurology 02/1996; 39(2):224-32. DOI:10.1002/ana.410390212 · 11.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Fanconi syndrome is an important presentation of respiratory chain disease. We report three patients who presented in the neonatal period with Fanconi syndrome, lactic acidosis and intrauterine growth retardation. In all three patients the major biochemical defect was in complex III of the mitochondrial respiratory chain, a relatively uncommon defect. The diagnosis could only be made by muscle biopsy as the defect was not expressed in cultured skin fibroblasts. Treatment with vitamins C and K3 and ubiquinone did not alter the course of the disease and all patients died before the age of 4 months.