Autosomal dominant optic atrophy and cataract
Autosomal dominant optic atrophy and cataract is an eye disorder characterized by progressive vision loss and lens clouding, often caused by mitochondrial dysfunction.
Overview
This disorder is characterized by impaired vision, which can range from nearly normal to complete blindness. While most affected individuals experience decreased visual acuity from birth, others may notice symptoms in early childhood or later. Both eyes are typically affected equally.
Symptoms
Vision impairment is caused by several factors:
- Retinal ganglion cell loss: A progressive loss of light-sensitive cells in the retina.
- Optic nerve atrophy: Degeneration of the nerves that relay visual information to the brain, often appearing as a pale color (pallor) during eye exams.
- Cataracts: Clouding of the eye lenses, typically appearing in childhood.
- Other eye problems: Involuntary eye movements (nystagmus) and color vision deficiency (difficulty distinguishing blue and green).
- Neurological symptoms: Some individuals experience balance and coordination problems (cerebellar ataxia), gait issues, tingling sensations (paresthesias), muscle stiffness (spasticity), tremors, or sensorineural deafness.
Causes
The condition is caused by mutations in the OPA3 gene. The OPA3 protein is located within mitochondria, the energy-producing centers of cells. While its exact function is not fully understood, it is believed to help organize mitochondrial structure and regulate controlled cell death (apoptosis).
Mutations lead to disorganized, poorly functioning mitochondria with reduced energy production. Cells with high energy demands, such as retinal ganglion cells, are particularly susceptible to premature death. When these cells die, the optic nerves atrophy and cannot transmit visual information to the brain. It is believed that similar mitochondrial dysfunction in other nerve cells leads to the neurological symptoms observed in some patients.
Inheritance
This condition is inherited in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition.