Lebers hereditary optic atrop... Health Article

Demographics

Males have LHON more often than females, however, females may develop LHON at a slightly older age and may have more severe symptoms, including a multiple sclerosis-like illness. Multiple sclerosis is a progressive degeneration of nerve cells that causes episodes of muscle weakness, dizziness, and visual disturbances, followed by remission. The onset of LHON usually occurs by 50 years if a mitochondrial DNA mutation is present, although it can present as late as the sixth or seventh decade of life.

Signs and symptoms

Symptoms of LHON include a painless sudden loss of central vision, both in visual detail and color, in both eyes over a period of weeks to months. Peripheral vision (seeing out of the corner of the eye) remains. Additional symptoms involving the neurological system may be present such as tremors, numbness or weakness in arms or legs, or loss of ankle reflexes. Symptoms vary by gender and type of mutation present. The following mutations are frequently identified and well understood:

• G11778A—the most common mutation and usually the most severe vision loss
• T14484C—usually has the best long term prognosis or outcome
• G3460A—has an intermediate presentation

Persons who have a multiple sclerosis-like illness can have any of the three mutations. This phenomena–where different mutations give different clinical outcomes–is called a genotype-phenotype correlation. The word genotype describes the specific findings in DNA, while the word phenotype is used to describe the clinical presentation.

Diagnosis

Suspicion of LHON is usually made by an ophthlamologist after a complete eye examination. Genetic testing for the presence/absence of mitochondrial mutations can then be performed from a small blood sample. After a symptomatic person with LHON in a family has been identified to have a mitochondrial mutation, other asymptomatic at-risk relatives can also be tested. At-risk relatives would include the affected persons' mother, siblings, and the offspring of any females found to have the mutation. Testing for asymptomatic children who are at-risk is not currently offered since no treatment is available for LHON; these individuals could opt for testing upon becoming a legal adult (i.e. reaching 18 years of age). Prenatal diagnosis for LHON is presently not available in the United States, but may be offered elsewhere. With genetic testing for LHON, it is important to remember that the presence of a mitochondrial mutation does not predict whether the condition will occur at all, the age at which it will begin, the severity, or rate of progression.

Treatment and management

There is no proven treatment available for LHON, although some studies report benefit from various vitamin therapies or other medications. Management of LHON is supportive, utilizing visual aids such as magnifiers.

Prognosis

The loss of central vision tends to remain the same (legally blind) over a lifetime once a person with LHON has reached the atrophic phase.

ORGANIZATIONS

International Foundation for Optic Nerve Disease. PO Box 777, Cornwall, NY 12518. <http://www.ifond.org>.

United Mitochondrial Diseases Foundation. PO Box 1151, Monroeville, PA 15146-1151. <http://www.umdf.org>.

WEBSITES

Leber's Optic Neuropathy. <http://www.leeder.demon.co.uk/pages/lhonhome.htm>.

Catherine L. Tesla, MS, CGC