Mutation m.15923A>G in the MT-TT gene causes mild myopathy - case report of an adult-onset phenotype
Only five patients have previously been reported to harbor mutations in the MT-TT gene encoding mitochondrial tRNA threonine. The m.15923A > G mutation has been found in three severely affected children. One of these patients died within days after birth and two had a phenotype of myoclonic epile...
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Published in | BMC neurology Vol. 18; no. 1; p. 149 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
England
BioMed Central
20.09.2018
BMC |
Subjects | |
Online Access | Get full text |
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Summary: | Only five patients have previously been reported to harbor mutations in the MT-TT gene encoding mitochondrial tRNA threonine. The m.15923A > G mutation has been found in three severely affected children. One of these patients died within days after birth and two had a phenotype of myoclonic epilepsy with ragged red fibers (MERRF) in early childhood. We have now found the mutation in an adult patient with mild myopathy.
The patient is a 64-year-old Finnish man, who developed bilateral ptosis, diplopia and exercise intolerance in his fifties. Family history was unremarkable. Muscle histology showed cytochrome c-oxidase (COX) negative and ragged red fibres. The m.15923A > G mutation heteroplasmy was 33% in the skeletal muscle and 2% in buccal epithelial cells. The mutation was undetectable in the blood. Single-fibre analysis was performed and COX-negative fibres had a substantially higher heteroplasmy of 92%, than the normal fibres in which it was 43%.
We report the fourth patient with m. 15923A > G and with a remarkably milder phenotype than the previous three patients. Our findings and recent biochemical studies suggest that the mutation m.15923A > G is a definite disease-causing mutation. Our results also suggest that heteroplasmy of the m.15923A > G mutation correlates with the severity of the phenotype. This study expands the catalog of the phenotypes caused by mutations in mtDNA. |
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Bibliography: | ObjectType-Case Study-2 SourceType-Scholarly Journals-1 ObjectType-Feature-4 content type line 23 ObjectType-Report-1 ObjectType-Article-3 |
ISSN: | 1471-2377 1471-2377 |
DOI: | 10.1186/s12883-018-1159-4 |