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Article
November 1993

Identical Twins Who Are Discordant for Leber's Hereditary Optic Neuropathy

Author Affiliations

From the Departments of Neurology (Drs Johns and Miller), Medicine (Dr Bias), and Ophthalmology (Dr Miller) and The Wilmer Ophthalmological Institute (Dr Miller), The Johns Hopkins University School of Medicine, Baltimore, Md; the Division of Ophthalmology, Scott and White Clinic, Temple, Tex (Dr Smith); and the Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia (Dr Sulewski). Dr Johns is now with Beth Israel Hospital, Harvard Medical School, Boston, Mass.

Arch Ophthalmol. 1993;111(11):1491-1494. doi:10.1001/archopht.1993.01090110057023
Abstract

Objective:  Leber's hereditary optic neuropathy is a maternally inherited form of visual loss that is associated with several mitochondrial DNA mutations. These mitochondrial DNA mutations are not the sole determinants of visual loss, as epigenetic factors may play a pathogenetic role. To clarify the role of these factors, we studied two visually discordant twins and determined their zygosity and mitochondrial genotype.

Design:  Case series.

Setting:  Referral center.

Patients:  Identical twin brothers from a family with the 11778 mitochondrial DNA mutation.

Main Outcome Measures:  Visual acuity, results of testing for visual fields (measured with static and dynamic perimetry) and color vision, and results of funduscopic examination; alcohol and tobacco use, head trauma, coexistent medical illness, and occupational exposure; and results of mitochondrial DNA analysis and determination of zygosity.

Results:  The monozygous twin brothers have remained discordant for the development of optic neuropathy for 6 ½ years despite harboring the identical homoplasmic 4216, 13708, and 11778 mitochondrial DNA mutations.

Conclusions:  The patients are visually discordant despite being genetically identical at the nuclear and mitochondrial levels. Epigenetic factors are important determinants of visual loss in Leber's hereditary optic neuropathy in these brothers. Among those factors studied in these patients, a substantial difference was noted in regard to occupational exposure to toxic substances. Epigenetic factors that may influence the clinical expression of the mitochondrial DNA mutations associated with Leber's hereditary optic neuropathy should be systematically studied. Risk-factor intervention strategies should be formulated and implemented.

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