Spastic Ataxia, Optic Atrophy, Mental Retardation
Patient Information
Characteristics
Background and History
The unique status of this disorder is in question. Many of the signs and symptoms are similar to those of other spastic ataxias and so far no responsible mutation has been identified. Only a few families have been reported.
Clinical Correlations
This is a progressive neurodegenerative disorder with onset in early childhood. Early symptoms include difficulty with balance and fine movement coordination, stiff limbs, and gait anomalies. Slurred speech, tremors, and hearing loss have also been observed. Mental function has not been quantified but dementia has been reported in one individual. The optic nerves (which carry visual messages to the brain) have been described as pale suggesting they are less than wholly functional but noting is known about vision.
Genetics
Inheritance
Evidence suggests autosomal recessive inheritance but specific mutation has been identified.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
Diagnosis is most likely made by a neurologist. The disorder is progressive but nothing is known regarding longevity or prognosis. No treatment is available for the neurologic deficits but physical and speech therapy are likely to be helpful in at least some patients.
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