Leber Hereditary Optic Neuropathy (LHON)
Description
Leber Hereditary Optic Neuropathy (LHON) is a rare, inherited mitochondrial disorder that primarily affects the optic nerve, leading to vision loss. This blog will delve into the intricacies of LHON, exploring its causes, symptoms, diagnosis, management, and strategies for living a fulfilling life despite the challenges.
Genes Involved
LHON is caused by mutations in mitochondrial DNA (mtDNA). Specifically, mutations in three genes are most commonly associated with LHON:
- ND1 (NADH dehydrogenase subunit 1): This gene is responsible for producing a protein involved in the electron transport chain, a critical process for cellular energy production.
- ND4 (NADH dehydrogenase subunit 4): Similar to ND1, this gene plays a role in the electron transport chain.
- ND6 (NADH dehydrogenase subunit 6): This gene also contributes to the electron transport chain and is involved in mitochondrial function.
Recognizing the Signs and Symptoms
LHON often manifests with sudden, painless vision loss, typically affecting one eye first. The vision loss is usually central, meaning it affects the ability to see straight ahead. Other symptoms may include:
- Blurred vision
- Distorted vision
- Difficulty distinguishing colors
- Increased sensitivity to light
- Eye pain
LHON can progress rapidly, with vision loss occurring over a few weeks or months. While vision loss can be severe in some cases, it is important to note that not everyone with LHON experiences complete blindness. Some individuals may experience partial vision loss, while others may retain good vision.
Causes
LHON is an inherited condition caused by mutations in mitochondrial DNA (mtDNA). Mitochondria are organelles within cells that are responsible for generating energy. Each cell contains hundreds of mitochondria, and each mitochondrion has its own DNA. Mutations in mtDNA can disrupt the normal function of mitochondria, leading to the development of LHON. These mutations are usually inherited from the mother, as mitochondria are passed down through the maternal line. However, there is a small chance of spontaneous mutations occurring in mtDNA.
Inheritance/recurrence risk
LHON follows a maternal inheritance pattern. This means that if a mother carries a mutation in her mtDNA, her children have a high chance of inheriting the mutation and developing LHON. The risk of inheriting the mutation depends on the number of mitochondria carrying the mutation in the mother‘s cells.
The chance of developing LHON can vary, even among siblings who inherit the same mutation. Other factors, including environmental triggers like exposure to tobacco smoke or alcohol, may also play a role in the development and progression of the disease.
