<i>TK2</i>-related Myopathic Mitochondrial Depletion Syndrome

Finsterer, Josef; Zarrouk‐Mahjoub, Sinda

doi:10.1177/1093526617743906

Cited by 1 publication

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“…MDS can be classified into three forms: myopathic, encephalomyopathic and hepatocerebral form according to clinical characteristics [3] and relevant different gene mutations. Genetically, mutations in thymidine kinase genes ( TK2 ) [4] and ribonucleotide reductase regulatory TP53 inducible subunit M2B ( RRM2B ) [5] are responsible for myopathic form of MDS, while mutations of SUCLA2 (succinate-CoA ligase ADP-forming beta subunit) [6] and SUCLG1 (succinate-CoA ligase alpha subunit) [7] are related to encephalomyopathic form of MDS. In addition, twinkle mtDNA helicase ( TWNK, OMIM # 606075), DNA polymerase gamma, catalytic subunit ( POLG ) [8, 9], the deoxyguanosine kinase ( DGUOK ) [10] and the recently stated mitochondrial inner membrane protein ( MPV17 ) [11] are the most common candidate genes of hepatocerebral form.…”

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confidence: 99%

Whole exome sequencing reveals two novel compound heterozygous mutations in TWNK as a cause of the hepatocerebral form of mitochondrial DNA depletion syndrome: a case report

Sun

et al. 2019

BMC Med Genet

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Background Although Mitochondrial DNA depletion syndrome (MDS) can be classified into three forms: myopathic, encephalomyopathic and hepatocerebral form, it is difficult to identify its form due to its clinical heterogeneity. Therefore, it is very important to conduct molecular genetic analysis on suspected patients. This study presented a male 38 weeks and 5 days infant with liver cytolysis and leukodystrophy. Case presentation A male infant proband was admitted to the department of NICU for feeding intolerance, irregular rhythm of respiration, hypoglycemia, lactic acidosis, liver cytolysis and neurological abnormalities. He was onset of mild jaundice with leukodystrophy and high lactate and phenylderivatives for urine organic acids on the 7th day. Whole exome sequencing (WES) and Sanger sequencing were performed to screen and confirm the suspicious pathogenic mutations. The results revealed this proband carried two compound heterozygous mutations in TWNK : c.1186 C > T / p.Pro396Ser and c.1844 G > C / p.Gly615Ala inherited by an autosomal recessive form from his parents, of which protein conservative analysis and structural modeling supported the pathogenicity of the two mutations. Unfortunately, the conditions described above were not improved until he was discharged from the hospital on the 23rd day and died at 4 months of age. Conclusions In this study, we investigated a Chinese family with the hepatocerebral form of MDS and conducted WES and Sanger sequencing to explore the causative mutations for this proband born from non-consanguineous and healthy parents. We identified two novel TWNK c.1186 C > T/ c.1844 G > C compound heterozygous mutations which were probably the disease-causing mutations of hepatocerebral form of MDS and described the clinical manifestations of the proband, which expanded the phenotypic spectrum of MDS caused by variants in TWNK . This study also emphasized WES technology can provide the genetic diagnosis of Mendelian genetic disease.

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