• Eri Imagawa, Aviva Fattal-Valevski, Ori Eyal, Satoko Miyatake, Ann Saada, Mitsuko Nakashima, Yoshinori Tsurusaki, Hirotomo Saitsu, Noriko Miyake, and Naomichi Matsumoto.
• Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
• J. Neurol. Neurosurg. Psychiatr. 2016 Feb 1; 87 (2): 212-6.

BackgroundLeigh syndrome (LS) is an early-onset progressive neurodegenerative disorder associated with mitochondrial dysfunction. LS is characterised by elevated lactate and pyruvate and bilateral symmetric hyperintense lesions in the basal ganglia, thalamus, brainstem, cerebral white matter or spinal cord on T2-weighted MRI. LS is a genetically heterogeneous disease, and to date mutations in approximately 40 genes related to mitochondrial function have been linked to the disorder.MethodsWe investigated a pair of female monozygotic twins diagnosed with LS from consanguineous healthy parents of Indian origin. Their common clinical features included optic atrophy, ophthalmoplegia, spastic paraparesis and mild intellectual disability. High-blood lactate and high-intensity signal in the brainstem on T2-weighted MRI were consistent with a clinical diagnosis of LS. To identify the genetic cause of their condition, we performed whole exome sequencing.ResultsWe identified a homozygous nonsense mutation in C12orf65 (NM_001143905; c.346delG, p.V116*) in the affected twins. Interestingly, the identical mutation was previously reported in an Indian family with Charcot-Marie Tooth disease type 6, which displayed some overlapping clinical features with the twins.ConclusionsWe demonstrate that the identical nonsense mutation in C12orf65 can result in different clinical features, suggesting the involvement of unknown modifiers.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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