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Spinocerebellar ataxia type 31

Synonym(s) SCA31
Prevalence Unknown
Inheritance Autosomal dominant
Age of onset Childhood
  • G11.8
MeSH -
MedDRA -


Disease definition

Spinocerebellar ataxia type 31 (SCA31) is a very rare subtype of autosomal dominant cerebellar ataxia type III (ADCA type III; see this term) characterized by the late-onset of cerebral ataxia, dysarthria and horizontal gaze nystagmus, and that is occasionally accompanied by pyramidal signs, tremor, decreased vibration sense and hearing difficulties.


SCA31 is the third most common form of ADCA (see this term) in Japan, where more than 20 families have been reported to date. It is rarely found in other Asian countries and is extremely rare in Western countries.

Clinical description

The mean age of disease onset is 58 years but it can present between the ages of 8 to 83 years. Ataxia, dysarthria, and horizontal gaze nystagmus are the common manifestations of SCA31 and the disease duration can be more than 10 years. Less common manifestations include pyramidal signs, tremor, decreased vibration sense, and hearing difficulties.


SCA31 is due to non-coding pentanucleotide repeat expansions in the BEAN1 gene (16q21), encoding protein BEAN1.

Genetic counseling

SCA31 is inherited autosomal dominantly with incomplete penetrance and genetic counseling is possible.

Expert reviewer(s)

  • Dr Shinsuke FUJIOKA
  • Dr Zbigniew WSZOLEK
  • Dr Shozaburo YANAMOTO

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Detailed information

Review article
Article for general public
Clinical genetics review
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