Summary about Disease
Leber Hereditary Optic Neuropathy (LHON) is a maternally inherited mitochondrial genetic disease that primarily affects the optic nerve, leading to acute or subacute central vision loss. It predominantly affects young adult males, although females can also be affected, typically with a later onset and lower penetrance. LHON is characterized by a painless, sequential loss of vision in both eyes.
Symptoms
The primary symptom of LHON is vision loss, which typically starts in one eye and progresses to the other eye within weeks or months. Other symptoms can include:
Blurred or cloudy vision
Difficulty distinguishing colors
Central scotoma (a blind spot in the center of the field of vision)
Rarely, neurological problems such as tremors, dystonia, or cardiac conduction abnormalities
Causes
LHON is caused by mutations in the mitochondrial DNA (mtDNA). These mutations primarily affect genes that encode subunits of complex I of the mitochondrial respiratory chain. The most common mutations are in the MT-ND4, *MT-ND6*, and *MT-ND1* genes. These mutations impair mitochondrial function and energy production, leading to optic nerve dysfunction. The disease is maternally inherited because mitochondria are passed down from the mother.
Medicine Used
Idebenone (Raxone): Approved in Europe for the treatment of LHON. It is a synthetic analog of coenzyme Q10 and is believed to improve mitochondrial function.
Vitamins and Supplements: Some doctors may recommend vitamins like B12 and antioxidants, though their effectiveness is not definitively proven.
Other: Research is ongoing to find better treatments.
Is Communicable
No, Leber Hereditary Optic Neuropathy (LHON) is not communicable. It is a genetic disease caused by mutations in mitochondrial DNA, which is inherited from the mother. It cannot be transmitted from person to person through any infectious means.
Precautions
Since LHON is a genetic condition, there are no specific precautions to prevent its onset for individuals who have inherited the causative mutation. However, general health recommendations apply:
Avoid smoking: Smoking is a known risk factor for vision loss in LHON carriers.
Limit alcohol consumption: Excessive alcohol intake may exacerbate the condition.
Maintain a healthy lifestyle: Adequate sleep, a balanced diet, and regular exercise may support overall health.
Genetic Counseling: Families with a history of LHON should seek genetic counseling to understand the risks of transmission and available reproductive options.
How long does an outbreak last?
LHON is not an "outbreak" like an infectious disease. The visual loss typically occurs over a period of weeks to months. The acute phase, where vision rapidly declines, may last several months. The vision loss is often permanent, but some individuals may experience partial recovery, particularly those with certain mutations or those treated with idebenone.
How is it diagnosed?
LHON is diagnosed based on a combination of clinical findings and genetic testing:
Clinical Examination: Ophthalmological examination including visual acuity testing, visual field testing, color vision testing, and fundoscopy (examination of the optic nerve). The optic nerve may appear swollen or pseudopapilledema-like in the acute phase.
Genetic Testing: Blood tests to detect the common mtDNA mutations associated with LHON.
Neuroimaging: MRI of the brain and orbits may be performed to rule out other causes of optic neuropathy.
Visual Evoked Potentials (VEP): Can assess the function of the optic nerve pathways.
Timeline of Symptoms
The typical timeline of LHON symptoms is as follows: 1. Early Stage (Subacute): Blurring or clouding of vision in one eye. 2. Progression: Vision loss progresses in the first eye, and similar symptoms develop in the second eye within weeks or months. 3. Acute Phase: Rapid decline in visual acuity in both eyes, leading to significant visual impairment. This phase typically lasts for several months. 4. Stabilization: Vision loss stabilizes, although the degree of vision loss can vary. Some individuals may experience some recovery, while others may have permanent severe visual impairment.
Important Considerations
Maternal Inheritance: LHON is inherited only from the mother. All children of a mother with LHON will inherit the mitochondrial mutation, but not all will develop symptoms (variable penetrance).
Variable Penetrance: Not everyone who inherits the LHON mutation will develop vision loss. Environmental factors, other genetic factors, and chance play a role in whether or not an individual becomes symptomatic. Males are more likely to develop symptoms than females.
Prognosis: The prognosis for visual recovery is variable. Some individuals may experience partial recovery of vision, particularly with idebenone treatment, while others may have permanent severe visual impairment.
Support and Rehabilitation: Low vision aids, orientation and mobility training, and psychological support can help individuals with LHON adapt to vision loss.
Differential Diagnosis: It is important to rule out other causes of optic neuropathy, such as multiple sclerosis, compressive lesions, or inflammatory conditions.