Background: Overlapping phenotypes including LHON, MELAS, and Leigh syndrome have recently been associated with numerous mtDNA point mutations in the ND5 gene of complex I, now considered a mutational hot spot.
Objective: To identify the mtDNA defect in a family with a prevalent ocular phenotype, including LHON-like optic neuropathy, retinopathy, and cataract, but characterised also by strokes, early deaths, and miscarriages on the maternal line.
Results: Sequencing of the entire mitochondrial genome from the proband’s muscle DNA identified the heteroplasmic 13042G→A transition, which was previously described only once in a patient with a different mitochondrial disease. This mutation fulfils the major pathogenic criteria, inducing an amino acid change (A236T) at an invariant position in a highly conserved domain of the ND5 gene. Phosphorus magnetic resonance spectroscopy in the proband disclosed an in vivo brain and skeletal muscle energy metabolism deficit.
Conclusions: These findings conclusively establish the pathogenic role of the 13042G→A mutation and underscore its variable clinical expression.
- FID, free induction decay
- LHON, Leber’s hereditary optic neuropathy
- MELAS, mitochondrial encephalomyopathy, lactic acidosis, stroke-like syndrome
- MERRF, myoclonic epilepsy, ragged red fibres
- mtDNA, mitochondrial DNA
- PCr, phosphocreatine
- complex I
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