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Clinical features of the pathogenic m.5540G>A mitochondrial transfer RNA tryptophan gene mutation.

ABSTRACT: Mitochondrial DNA disease is one of the most common groups of inherited neuromuscular disorders and frequently associated with marked phenotypic and genotypic heterogeneity. We describe an adult patient who initially presented with childhood-onset ataxia without a family history and an unremarkable diagnostic muscle biopsy. Subsequent multi-system manifestations included basal ganglia calcification, proteinuria, cataract and retinitis pigmentosa, prompting a repeat muscle biopsy that showed features consistent with mitochondrial myopathy 13 years later. She had a stroke with restricted diffusion change in the basal ganglia and internal capsule at age 44 years. Molecular genetic testing identified a previously-reported pathogenic, heteroplasmic mutation in the mitochondrial-encoded transfer RNA tryptophan (MT-TW) gene which based on family studies was likely to have arisen de novo in our patient. Interestingly, we documented an increase in the mutant mtDNA heteroplasmy level in her second biopsy (72% compared to 56%), reflecting the progression of clinical disease.

SUBMITTER: Ng YS

PROVIDER: S-EPMC5066368 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Clinical features of the pathogenic m.5540G>A mitochondrial transfer RNA tryptophan gene mutation.

Ng Yi Shiau YS Hardy Steven A SA Shrier Venice V Quaghebeur Gerardine G Mole David R DR Daniels Matthew J MJ Downes Susan M SM Freebody Jane J Fratter Carl C Hofer Monika M Nemeth Andrea H AH Poulton Joanna J Taylor Robert W RW

Neuromuscular disorders : NMD 20160817 10

Mitochondrial DNA disease is one of the most common groups of inherited neuromuscular disorders and frequently associated with marked phenotypic and genotypic heterogeneity. We describe an adult patient who initially presented with childhood-onset ataxia without a family history and an unremarkable diagnostic muscle biopsy. Subsequent multi-system manifestations included basal ganglia calcification, proteinuria, cataract and retinitis pigmentosa, prompting a repeat muscle biopsy that showed feat ...[more]

PMID: 27618137

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Project description:IntroductionIodothyronine deiodinases are selenoproteins with the amino acid selenocysteine (Sec) introduced into the position of a TGA stop codon by a complex machinery involving tRNA[Ser]Sec when a cis-acting Sec-insertion sequence element is present in the 3' end of the mRNA. Recently, a variant in the TRU-TCA1-1 gene encoding for tRNA[Ser]Sec was reported, which resulted in reduced expression of stress-related selenoproteins. The proband presented with multisystem symptoms, euthyroid hyperthyroxinemia, and selenium deficiency. Here, we describe 2 new members of a family harboring the same tRNA[Ser]Sec variant.Case presentationA 13-year-old patient was seen for Hashimoto's disease with high FT3 (4.6 pg/mL, normal range 2-4.2 pg/mL) and normal FT4 and TSH concentrations. He had no clinical complaints. During a 6-year clinical and hormonal follow-up, the index patient was not treated, FT3 decreased, FT4 increased, and serum TSH stayed in the normal range resulting in a euthyroid hyperthyroxinemia. Reverse T3 concentration was significantly increased at the last visit (19 years and 4 months). At the last evaluation, the total selenium level was low (91 μg/L, normal range 95-125). DNA sequencing identified a germinal homozygous variant (C65G) in the TRU-TCA1-1 gene. During follow-up, no additional clinical symptom was observed in the absence of any treatment. The same germinal tRNA[Ser]Sec variant was identified at heterozygous state in his father, who had normal thyroid function tests except a moderately increased reverse T3 concentration, with increased total selenium (143 μg/L) level. In both patients, the expression of stress-related selenoprotein GPX3 was in the low-normal range (168 and 180 IU/L, respectively, normal range: 150-558 IU/L). We did not find any significant biological abnormalities evocative of other selenoprotein deficiencies.Discussion/conclusionWe report on 2 members of a family with a variant in the TRU-TCA1-1 gene encoding for tRNA[Ser]Sec. Our study suggests that this tRNA[Ser]Sec variant is not exclusively causative of disruption in selenoprotein synthesis.

Dataset Information

Clinical features of the pathogenic m.5540G>A mitochondrial transfer RNA tryptophan gene mutation.

Publications

Clinical features of the pathogenic m.5540G>A mitochondrial transfer RNA tryptophan gene mutation.

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