autosomal recessive spinocerebellar ataxia

Spinocerebellar Ataxia 18

Clinical Characteristics
Ocular Features: 

Ocular signs in SCAR18 include nystagmus, oculomotor apraxia, and optic atrophy.  The nystagmus may be rotatory or horizontal and can be gaze-evoked.  Some patients have intermittent and tonic upgaze.  Visual acuity has not been reported.

Systemic Features: 

Patients are developmentally delayed and have intellectual disability.  These features do not seem to be progressive.  Ataxia, both truncal and cerebellar, is present.  Mobility is impaired from early childhood and eventually requires assistance.   Joint contractures sometimes develop and patients can be wheelchair-bound by the second decade.  Dysarthric speech is common.  No dysmorphic facial features are present.

Brain imaging shows progressive cerebellar and sometimes cerebral atrophy.

Genetics

This autosomal recessive disorder results from homozygous deletions in the GRID2 gene (4q22).  This gene codes for a subunit of the glutamate receptor channel and is thought to be selectively expressed in the Purkinje cells of the cerebellum.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.  However, physical therapy, assistive devices for mobility, and low vision aids may be helpful.

References
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