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Severe infantile leigh syndrome associated with a rare mitochondrial ND6 mutation, m.14487T>C


  • Conflict of interest: Drs. Sheldon and Boles are employees of Courtagen Diagnostic Laboratory.

Correspondence to:

Mark Tarnopolsky, M.D., Ph.D., Professor of Neuromuscular and Neurometabolic Disease, Department of Pediatrics, 1200 Main Street W., HSC-2H26, Hamilton ON, L8N 3Z5 Canada.



We describe a case of severe infantile-onset complex I deficiency in association with an apparent de novo near-homoplasmic mutation (m.14487T>C) in the mitochondrial ND6 gene, which was previously associated with Leigh syndrome and other neurological disorders. The mutation was near-homoplasmic in muscle by NextGen sequencing (99.4% mutant), homoplasmic in muscle by Sanger sequencing, and it was associated with a severe complex I deficiency in both muscle and fibroblasts. This supports previous data regarding Leigh syndrome being on the severe end of a phenotypic spectrum including progressive myoclonic epilepsy, childhood-onset dystonia, bilateral striatal necrosis, and optic atrophy, depending on the proportion of mutant heteroplasmy. While the mother in all previously reported cases was heteroplasmic, the mother and brother of this case were homoplasmic for the wild-type, m.14487T. Importantly, the current data demonstrate the potential for cases of mutations that were previously reported to be homoplasmic by Sanger sequencing to be less homoplasmic by NextGen sequencing. This case underscores the importance of considering mitochondrial DNA mutations in families with a negative family history, even in offspring of those who have tested negative for a specific mtDNA mutation. © 2013 Wiley Periodicals, Inc.