Recessive twinkle mutations cause severe epileptic encephalopathy.
ABSTRACT The C10orf2 gene encodes the mitochondrial DNA helicase Twinkle, which is one of the proteins important for mitochondrial DNA maintenance. Dominant mutations cause multiple mitochondrial DNA deletions and progressive external ophthalmoplegia, but recent findings associate recessive mutations with mitochondrial DNA depletion and encephalopathy or hepatoencephalopathy. The latter clinical phenotypes resemble those associated with recessive POLG1 mutations. We have previously described patients with infantile onset spinocerebellar ataxia (MIM271245) caused either by homozygous (Y508C) or compound heterozygous (Y508C and A318T) Twinkle mutations. Our earlier reports focused on the spinocerebellar degeneration, but the 20-year follow-up of 23 patients has shown that refractory status epilepticus, migraine-like headaches and severe psychiatric symptoms are also pathognomonic for the disease. All adolescent patients have experienced phases of severe migraine, and seven patients had antipsychotic medication. Epilepsia partialis continua occurred in 15 patients leading to generalized epileptic statuses in 13 of them. Eight of these patients have died. Valproate treatment was initiated on two patients, but had to be discontinued because of a severe elevation of liver enzymes. The patients recovered, and we have not used valproate in infantile onset spinocerebellar ataxia since. The first status epilepticus manifested between 15 and 34 years of age in the homozygotes, and at 2 and 4 years in the compound heterozygotes. The epileptic statuses lasted from several days to weeks. Focal, stroke-like lesions were seen in magnetic resonance imaging, but in infantile onset spinocerebellar ataxia these lesions showed no predilection. They varied from resolving small cortical to large hemispheric oedematous lesions, which reached from cerebral cortex to basal ganglia and thalamus and caused permanent necrotic damage and brain atrophy. Brain atrophy with focal laminar cortical necrosis and hippocampal damage was confirmed on neuropathological examination. The objective of our study was to describe the development and progression of encephalopathy in infantile onset spinocerebellar ataxia syndrome, and compare the pathognomonic features with those in other mitochondrial encephalopathies.
- SourceAvailable from: Anu Suomalainen Wartiovaara[show abstract] [hide abstract]
ABSTRACT: Mutations in the catalytic subunit of the mitochondrial DNA polymerase gamma (POLG) have been found to be an important cause of neurological disease. Recently, we and collaborators reported a new neurodegenerative disorder with autosomal recessive ataxia in four patients homozygous for two amino acid changes in POLG: W748S in cis with E1143G. Here, we studied the frequency of this allele and found it to be among the most common genetic causes of inherited ataxia in Finland. We identified 27 patients with mitochondrial recessive ataxia syndrome (MIRAS) from 15 Finnish families, with a carrier frequency in the general population of 1 : 125. Since the mutation pair W748S+E1143G has also been described in European patients, we examined the haplotypes of 13 non-Finnish, European patients with the W748S mutation. Haplotype analysis revealed that all the chromosomes carrying these two changes, in patients from Finland, Norway, the United Kingdom, and Belgium, originate from a common ancient founder. In Finland and Norway, long, common, northern haplotypes, outside the core haplotype, could be identified. Despite having identical homozygous mutations, the Finnish patients with this adult- or juvenile-onset disease had surprisingly heterogeneous phenotypes, albeit with a characteristic set of features, including ataxia, peripheral neuropathy, dysarthria, mild cognitive impairment, involuntary movements, psychiatric symptoms, and epileptic seizures. The high carrier frequency in Finland, the high number of patients in Norway, and the ancient European founder chromosome indicate that this newly identified ataxia should be considered in the first-line differential diagnosis of progressive ataxia syndromes.The American Journal of Human Genetics 10/2005; 77(3):430-41. · 11.20 Impact Factor
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ABSTRACT: Infantile onset spinocerebellar ataxia with sensory neuropathy is a new, inherited multisystem disorder discovered in 19 Finnish patients. In order to define the neuropathy of the disease, we measured sensory nerve action potentials and nerve conduction velocities in 18 patients, and recorded somatosensory evoked potentials (SEP) in 10 patients and performed a sural nerve biopsy in 13 patients. The fixed and teased nerve fascicles were examined by light and electron microscopy, and the whole transverse section of a nerve fascicle was photographed and enlarged for morphometric measurements. Our investigation revealed an early onset, rapidly progressive axonal neuropathy: the sensory action potentials were decreased after the age of 2 and a severe loss of mainly large myelinated fibers was found.Muscle & Nerve 06/1994; 17(5):509-15. · 2.31 Impact Factor
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ABSTRACT: Mitochondria are intracellular organelles involved in adenosine triphosphate production. The literature has established the presence of mitochondrial dysfunction in some subjects with psychiatric disorders. Also, there are multiple reports of patients with mitochondrial dysfunction who have various psychiatric disorders. Although the literature on mitochondrial dysfunction and its relation to psychiatric disorders is growing, there remain many unanswered questions. To review subjects with mitochondrial cytopathies for prevalence of psychiatric comorbidity. For this study, 36 adults were interviewed. The Mini International Neuropsychiatric Interview and the Short-Form 36 Health Survey, version 1 were used. Lifetime diagnoses included 54% major depressive disorder, 17% bipolar disorder, and 11% panic disorder. These prevalence rates are compared with the general population and subjects with cancer and epilepsy. Subjects with a comorbid psychiatric diagnosis were older (P=.05), had more hospital admissions (P=.02), more medical conditions (P=.01), and lower quality of life (P=.01) than subjects with mitochondrial disease alone. Clinicians caring for persons with mitochondrial cytopathies should note the high prevalence of psychiatric problems. Also, this comorbidity might have etiological and therapeutic implications.CNS spectrums 07/2007; 12(6):429-38. · 1.73 Impact Factor