Spinocerebellar ataxia 17
SCA17

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Description from OMIM

SCA17 is an autosomal dominant neurologic disorder characterized by ataxia, pyramidal and extrapyramidal signs, cognitive impairments, psychosis, and seizures. Its clinical phenotype and inheritance pattern are similar to Huntington disease (HD; 143100). Individuals with normal TBP alleles have between 25 and 44 repeats, whereas SCA17 patients have between 47 and 63 repeats. Reduced penetrance is seen with 45 to 46 repeats (summary by Gao et al. (2008)).



Prevalence of clinical parameters (%)







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Number of patients in the reference Percent affected patients (Between 0 and 1, eg. 0.1 = 10%)
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List of symptoms



Symptom/sign Organ system Percent affected Pubmed id Added on(yyyy-mm-dd) Edit/add reference
Cerebral atrophy nervous 100 % 17934876 2015-01-10
Cerebellar atrophy nervous 100 % 17934876 2015-01-10
Ataxia nervous 87 % 12953269 2015-01-10
Dementia nervous 80 % 17934876 2015-01-10
Cerebellar atrophy nervous 70 % 12953269 2015-01-10
Chorea nervous 66 % 17934876 2015-01-10
Dysarthria nervous 60 % 12953269 2015-01-10
Dystonia nervous 50 % 17934876 2015-01-10
Pyramidal signs nervous 50 % 17934876 2015-01-10
Bradykinesia nervous 50 % 17934876 2015-01-10
Psychiatric symptom nervous 47 % 12953269 2015-01-10
Dementia nervous 47 % 12953269 2015-01-10
Slow saccades nervous 40 % 12953269 2015-01-10
Dystonia nervous 40 % 12953269 2015-01-10
Dysphagia nervous 40 % 12953269 2015-01-10
Hyperactive reflexes nervous 33 % 12953269 2015-01-10
Dysmetria nervous 27 % 12953269 2015-01-10
Chorea nervous 20 % 12953269 2015-01-10
Hypogonadism endocrine 13 % 12953269 2015-01-10
Tremor nervous 13 % 12953269 2015-01-10
Nystagmus nervous 13 % 12953269 2015-01-10



List of references:


Spinocerebellar ataxia type 17 (SCA17): oculomotor phenotype and clinical characterization of 15 Italian patients.
Caterina Mariotti, Dario Alpini, Roberto Fancellu, Paola Soliveri, Marina Grisoli, Sabrina Ravaglia, Carlo Lovati, Vincenza Fetoni, Giorgio Giaccone, Alessia Castucci, Franco Taroni, Cinzia Gellera, Stefano Di Donato,

SCA17 is a rare type of autosomal dominant spinocerebellar ataxia caused by a CAG/CAA expansion in the gene encoding the TATA-binding protein (TBP). We screened for triplet expansion in the TBP gene 110 subjects with progressive cerebellar ataxia and 94 subjects with Huntington-like phenotype negative at specific molecular tests. SCA17 mutation-positive subjects were found in both groups of patients. Expanded alleles with > or = 44 CAG/CAA repeats were identified in 11 individuals and in 4 non-symptomatic relatives. Eleven de novo diagnosed patients and four patients previously reported underwent extensive clinical, neuroradiological and oculographic examination. Cerebellar signs and symptoms were present in all cases; 80% of the patients had mild to severe cognitive deficits; 66% of patients showed choreic movements; pyramidal signs, bradykinesia and dystonia were observed in approx 50% of the cases. MRI demonstrated cortical and cerebellar atrophy in all patients, whereas neurophysiological examination excluded signs of peripheral nervous system involvement. Oculographic examinations were performed in 9 out of 15 patients and showed a distinct pattern of oculomotor abnormalities, characterized by impairment of smooth pursuit, defects in the saccade accuracy, normal saccade velocity, hyperreflexia of vestibuloocular reflexes, and absence of nystagmus. In summary, this study presents one of the largest series of SCA17 patients in Europe. In our group of patients, SCA17 represents the third most frequent SCA genotype. Our clinical data confirm the large variability in SCA17 phenotypic presentation, and indicate that a peculiar combination of neuroradiological, electrophysiological and oculomotor findings is recognizable in SCA17.

Journal of neurology - Nov 2007



Clinical features and neuropathology of autosomal dominant spinocerebellar ataxia (SCA17).
Arndt Rolfs, Arnulf H Koeppen, Ingrid Bauer, Peter Bauer, Sven Buhlmann, Helge Topka, Ludger Schöls, Olaf Riess,

Autosomal dominant spinocerebellar ataxias (SCAs) are a group of neurodegenerative disorders clinically characterized by late-onset ataxia and variable other manifestations. Genetically and clinically, SCA is highly heterogeneous. Recently, CAG repeat expansions in the gene encoding TATA-binding protein (TBP) have been found in a new form of SCA, which has been designated SCA17. To estimate the frequency of SCA17 among white SCA patients and to define the phenotypic variability, we determined the frequency of SCA17 in a large sample of 1,318 SCA patients. In total, 15 patients in four autosomal dominant SCA families had CAG/CAA repeat expansions in the TBP gene ranging from 45 to 54 repeats. The clinical features of our SCA17 patients differ from other SCA types by manifesting with psychiatric abnormalities and dementia. The neuropathology of SCA17 can be classified as a "pure cerebellar" or "cerebello-olivary" form of ataxia. However, intranuclear neuronal inclusion bodies with immunoreactivity to anti-TBP and antipolyglutamine were much more widely distributed throughout the brain gray matter than in other SCAs. Based on clinical and genetic data, we conclude that SCA17 is rare among white SCA patients. SCA17 should be considered in sporadic and familial cases of ataxia with accompanying psychiatric symptoms and dementia.

Annals of neurology - Sep 2003