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The natural history of infantile mitochondrial DNA depletion syndrome due to RRM2B deficiency

Keshavan, Nandaki, Abdenur, Jose, Anderson, Glenn, Assouline, Zahra, Barcia, Giulia, Bouhikbar, Lamia, Chakrapani, Anupam, Cleary, Maureen, Cohen, Marta C., Feillet, François, Fratter, Carl, Hauser, Natalie, Jacques, Tom, Lam, Amanda, McCullagh, Helen, Phadke, Rahul, Rötig, Agnès, Sharrard, Mark, Simon, Mariella, Smith, Conrad, Sommerville, Ewen W., Taylor, Robert W., Yue, Wyatt W. and Rahman, Shamima 2020. The natural history of infantile mitochondrial DNA depletion syndrome due to RRM2B deficiency. Genetics in Medicine 22 , pp. 199-209. 10.1038/s41436-019-0613-z

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Purpose Mitochondrial DNA (mtDNA) depletion syndrome (MDDS) encompasses a group of genetic disorders of mtDNA maintenance. Mutation of RRM2B is an uncommon cause of infantile-onset encephalomyopathic MDDS. Here we describe the natural history of this disease. Methods Multinational series of new genetically confirmed cases from six pediatric centers. Results Nine new cases of infantile-onset RRM2B deficiency, and 22 previously published cases comprised a total cohort of 31 patients. Infants presented at a mean of 1.95 months with truncal hypotonia, generalized weakness, and faltering growth. Seizures evolved in 39% at a mean of 3.1 months. Non-neurological manifestations included respiratory distress/failure (58%), renal tubulopathy (55%), sensorineural hearing loss (36%), gastrointestinal disturbance (32%), eye abnormalities (13%), and anemia (13%). Laboratory features included elevated lactate (blood, cerebrospinal fluid (CSF), urine, magnetic resonance (MR), spectroscopy), ragged-red and cytochrome c oxidase–deficient fibers, lipid myopathy, and multiple oxidative phosphorylation enzyme deficiencies in skeletal muscle. Eight new RRM2B variants were identified. Patients with biallelic truncating variants had the worst survival. Overall survival was 29% at 6 months and 16% at 1 year. Conclusions Infantile-onset MDDS due to RRM2B deficiency is a severe disorder with characteristic clinical features and extremely poor prognosis. Presently management is supportive as there is no effective treatment. Novel treatments are urgently needed.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Publisher: Springer Nature
ISSN: 1098-3600
Date of First Compliant Deposit: 16 September 2019
Date of Acceptance: 9 July 2019
Last Modified: 16 Mar 2020 04:15

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