Leber Hereditary Optic Neuropathy
What else is it called?
- Hereditary optic neuroretinopathy
- Leber hereditary optic atrophy
- Leber optic atrophy
- Leber’s hereditary optic neuropathy
- Leber’s optic atrophy
- Leber’s optic neuropathy
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What causes it?
The disorder is caused by a problem in either the MT-ND1, MT-ND4, MT-ND4L, or MT-ND6 gene. These genes provide instructions for proteins that are used to change oxygen, fats, and sugars into a form of energy that your body can use.
The genes are found in your mitochondria, which are a part of your cells’ structure that help with breathing and converting energy. They are important for maintaining the cells in your body.
If you have a problem in either the MT-ND1, MT-ND4, MT-ND4L, or MT-ND6 gene, you will not be able to convert oxygen, fats, and sugars into energy effectively. This causes the cells in your optic nerve to die, which leads to sudden loss of sight.
Currently, it is not clear exactly how the mutation causes Leber Hereditary Optic Neuropathy.
How common is it?
The amount of people with Leber Hereditary Optic Neurology is unknown. It is estimated that 1 in every 30,000-50,000 people in the UK may be affected by the disorder. However, worldwide it could be more prevalent, and has been estimated to affect around 1 in 15,000 people in some studies.
The disorder mostly affects males, with three times more males diagnosed than females. However, females are likely to suffer from a more severe form of the disorder. It is not known why this is the case.
Leber Hereditary Optic Neurology typically presents in young adulthood, and any sight loss is usually experienced before the age of 40. It can occur later in life or in childhood, although this is very rare.
What are the signs and symptoms?
The main symptom of Leber Hereditary Optic Neurology is a sudden loss of central vision, which usually occurs between the ages of 18 and 30. Typically, it affects the sharpness of images (visual acuity) and colour vision. It can affect both eyes simultaneously or one may lose sight a number of weeks or months after the first. Both eyes tend to be affected equally around 15 months after the onset of the disorder. Your vision may get worse as time passes, and the deterioration is permanent in the majority of cases.
Some people are diagnosed with Leber Hereditary Optic Neurology Plus (or LHON+). With this strain of the disorder, as well as a loss of vision, you will experience:
- Movement disorders
- Abnormal heartbeat (cardiac conduction defects)
A small number of people also have symptoms like muscle weakness, poor coordination, and numbness that may, at first, be mistaken for multiple sclerosis.
Many people with this disorder can expect an average life expectancy, however this is dependent on the severity of your symptoms. It may be reduced for people with Leber Hereditary Optic Neurology Plus due to the nature of the symptoms.
How is it diagnosed?
Leber Hereditary Optic Neurology is diagnosed using an eye examination (ophthalmoscopic examination) and a specialised eye scan (optical coherence tomography). Your medical team may also conduct an MRI or PET scan to examine your brain and rule out other disorders. Genetic testing is also used to confirm the presence of the faulty gene.
During the diagnostic phase, other eye-related illnesses and disorders may be considered. These can include Mohr-Tranebjaerg Syndrome, optic neuropathies, and Leber’s Congenital Amaurosis.
A large percentage of people with the mutated genes may never experience Leber Hereditary Optic Neurology. It is believed that there are other factors, possibly in relation to lifestyle or environment, that interact with the mutated gene to cause the disorder. However, it is currently not known what these factors may be, and research into this is ongoing.
Can it be treated?
There is currently no cure for Leber Hereditary Optic Neurology. Despite this, there are treatments using supplements and vitamins that can reduce the symptoms. This is particularly effective if treatment is started during the early stages of the disorder.
New orphan drugs are being trialled that aim to regain some of your vision. The drug Idebenone has proven effective after a year of regular treatment, and more drugs are currently being tested. It is important to avoid smoking tobacco and drinking alcohol whilst taking these treatments. Some antibiotics can also interfere with these drugs, so ensure you discuss this with your doctor before taking any other medications.
You will be offered visual tools, suitable for your personal requirements, to help support you.
Currently, most people with Leber Hereditary Optic Neurology do not regain their sight, but it is rare to become completely blind. Most people with the disorder are legally registered as severely sight impaired. Although this means that you are unable to hold a driving licence, it may also allow you to access extra support.
Many people with the disorder also struggle to find appropriate employment due to the limitations they face. There are charities that can help to support you in the workplace.
Do my family need to be tested?
Leber Hereditary Optic Neurology is always inherited from your mother. It is inherited in what is called a mitochondrial pattern.
Information about the mitochondria is always inherited from the mother. This means that a female with the condition will pass it on to any children that she has. A male with the condition will never pass it on to his children because he does not provide the genetic information for mitochondria.