This is one of a large number of hereditary neurological disorders that is caused by a specific mutation.
This is a progressive disorder. Most symptoms have their onset late in the first decade of life. These consist of clumsy walking and decreased vision. Vision is variably affected from moderate to severe loss. There may also be some sensory changes such as loss of fine touch. Examination reveals increased reflexes in the limbs and atrophy (degeneration) of the optic nerves. Cognitive functions are not affected and patients are able to lead independent lives. Nerve studies show deficits in motor nerves impulses that control muscles but not in sensory nerves. Later in life some individuals develop a ‘club foot’.
MRI imaging of the brain reveals some atrophy of specific structures.
Two copies of a specific gene mutation are required for this disease to become evident. Carrier parents who have only one copy of the mutation are clinically normal. However, when both parents carry the mutation there is a 25% risk in each of their children to inherit this condition.
The diagnosis is usually made late in the first decade of life due to an abnormal gait and vision complaints. Prior to then the disorder could be made by identification of the gene mutations. Neurologists and ophthalmologists are likely to collaborate in the diagnosis.
There does not seem to be an impact on longevity and patients are capable of living independently. Physical therapy should begin early in an effort to prevent joint contractures and ‘club feet’. Low vision aids could be helpful especially during school activities.