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Study shows tenuous link between bilateral optic neuropathy, mitochondrial defects
Invest Ophthalmol Vis Sci. 2008;49(12):5250-5256.
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A minority of young patients with sporadic bilateral optic neuropathy had mitochondrial disease, suggesting that their disability resulted from other genetic or environmental factors or from mitochondrial defects not studied.
The case-control study, conducted in Saudi Arabia, included 21 unrelated patients with isolated, early-onset, bilateral optic neuropathy, 159 controls for mitochondrial DNA sequencing and 40 controls for relative mitochondrial DNA content. Mean patient age at first examination was 13.6 years.
Only one patient had the Leber’s hereditary optic neuropathy mutation, the most common mitochondrial syndrome. Three patients had mitochondrial DNA nucleotide changes that may have been pathologic. No patients had polymorphism or mutation of the OPA1 or OPA3 genes associated with optic atrophy. The group of patients had a small increase in relative mitochondrial DNA content.
The study had drawbacks because only two mitochondrial parameters — sequencing the mitochondrial genome and measuring relative mtDNA content — were evaluated. Also, the patient group was relatively small and represented one ethnic group.
“Therefore, our findings require confirmation by studying these and other mitochondrial parameters in other ethnic groups before they can be more generally applied in predicting likelihood of mitochondrial disease,” the study authors said. “Nevertheless, these observations provide insight into the limited influence of mitochondrial abnormalities in the pathogenesis of sporadic, childhood-onset, bilateral optic neuropathy.”