Leber hereditary optic neuropathy (LHON) is mainly characterized by bilateral, painless subacute loss of central vision during young adult life. In most cases, symptoms begin with one eye first, followed a few weeks later by visual failure in the other eye. Extremely rarely there may be neurologic abnormalities, such as peripheral neuropathy, postural tremor, nonspecific myopathy, and movement disorders. LHON is caused by mutations in mitochondrial DNA and it is transmitted by maternal inheritance. LHON affects approximately 1:50,000 people. Many carriers never suffer significant visual loss; males are about four to five times more likely than females to be affected.
Individuals with LHON typically display symptoms in their young adult years. If vision is lost, then it usually occurs before 40 years of age.
The acute phase of LHON is characterized by a loss of central vision, including blurring and reduced perception of color. Individuals usually lose vision in one eye first and then lose vision in the other eye after two to three months. The atrophic phase is characterized by bilateral optic atrophy, resulting in lifelong blindness.
Depending on the mutation and pedigree, most female carriers do not lose vision but upt to half of males do.
LHON is caused by genetic mutations in the mitochondrial DNA (mtDNA). Some mothers with a LHON gene mutation do not show symptoms, but family history often reveals female relatives with visual loss at an early age.
Mutations in mitochondrial DNA can only be inherited maternally because ova contain mitochondria, while sperm do not. All of the offspring of a mother with an mtDNA mutation will inherit the gene. A male with a mitochondrial DNA mutation cannot transmit the mutated gene to any of his children.
The three primary mitochondrial DNA LHON-causing mutations are mt.3460G>A, mt.11778G>A, and mt.14484T>C, which account for over 90% of LHON patients. The most common LHON-causing mutation is mt.11778G>A. The greatest penetrance (chance of a carrier to lose vision) is for mt.3460G>A and the least is for mt.14484 T>C.
LHON affects both males and females and can only be inherited from a female. The birth prevalence of LHON is approximately 1 in 50,000 people.
LHON is diagnosed based on ophthalmologic findings, which include specialized visual testing. The testing involves dilated fundus examination to identify characteristic changes in the optic disc and vascular changes during the acute phase, electrophysiologic studies, and neuroimaging. Molecular genetic testing for mitochondrial genes associated with LHON can be used to confirm diagnosis. Most affected individuals know if their family members also are affected by LHON.
Clinical Testing and Work-Up
Consistent monitoring and surveillance of asymptomatic individuals with LHON-causing mutations is not necessary. However, if visual disturbance is experienced, affected individuals should immediately seek medical attention from an ophthalmologist or neuro-ophthalmologis. .
Individuals should follow-up frequent to their own circumstances and availability of local healthcare.
Affected individuals should receive supportive management and treatment through the usage of visual aids, occupational rehabilitation, and local social services. Small studies have shown that therapies involving ubiquinone and idebenone may provide possible benefits during the acute phase of the disorder. Affected individuals should avoid smoking and excessive alcohol consumption, which causes stress to mitochondrial energy production.
Genetic counseling may be of assistance to patients and their families.
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Contact for additional information about Leber hereditary optic neuropathy:
Alfredo A. Sadun, MD, PhD
Flora Thornton Professor of Vision Research
Chief of Service, Neuro-Ophthalmology
Professor of Neuro-surgery
Keck-USC School of Medicine
1450 San Pablo St., Suite 5802
Los Angeles, CA 90033
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