SCAR7

Spinocerebellar Ataxia, Autosomal Recessive 7

Clinical Characteristics
Ocular Features: 

Nystagmus and saccadic pursuit eye movements are common signs.  Some patients complain of diplopia.  No other ocular abnormalities are present.

Systemic Features: 

Symptoms have their onset in late childhood and are slowly progressive.  Walking and balancing are difficult.  Dysarthria, postural tremor, and limb ataxia are evident in adults.  Fine motor movements are difficult and there is often a tremor in the hands.  Deep tendon reflexes are abnormally brisk and extensor plantar responses are seen in some individuals.  Vibration sense may be diminished.  These signs are variable as is the rate of progression.  Usually patients remain mobile and productive through the fourth decade of life.  They may become wheelchair-bound by the fifth or sixth decade.  There is no cognitive impairment.

Genetics

This is an autosomal recessive condition secondary to homozygous mutations in TPP1(11p15).

The same gene is mutated in neuronal ceroid lipofuscinosis 2 (CLN2, 204500), a far more serious condition with epilepsy, optic atrophy, retinal degeneration, and a rapidly progressive course leading to early death in many individuals. It has been suggested that mutations resulting in the more severe CLN2 phenotype completely or nearly completely abolish TPP1 enzyme activity whereas those that cause SCAR7 simply result in diminished activity.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is known for the neurological symptoms but physical therapy and mobility devices could be helpful in maintaining ambulation.  Speech therapy could be useful for dysarthria.

References
Article Title: 

Autosomal Recessive Spinocerebellar Ataxia 7 (SCAR7) is Caused by Variants in TPP1, the Gene Involved in Classic Late-Infantile Neuronal Ceroid Lipofuscinosis 2 Disease (CLN2 Disease)

Sun Y, Almomani R, Breedveld GJ, Santen GW, Aten E, Lefeber DJ, Hoff JI, Brusse E, Verheijen FW, Verdijk RM, Kriek M, Oostra B, Breuning MH, Losekoot M, den Dunnen JT, van de Warrenburg BP, Maat-Kievit AJ. Autosomal Recessive Spinocerebellar Ataxia 7 (SCAR7) is Caused by Variants in TPP1, the Gene Involved in Classic Late-Infantile Neuronal Ceroid Lipofuscinosis 2 Disease (CLN2 Disease). Hum Mutat. 2013 Feb 15. [Epub ahead of print].

PubMed ID: 
23418007
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