Spinocerebellar ataxia type 31 (SCA31) is a very rare subtype of autosomal dominant cerebellar ataxia type 3 (ADCA type 3; 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.
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.
SCA31 is inherited autosomal dominantly with incomplete penetrance and genetic counseling is possible.
Last update: November 2014
- Dr Shinsuke FUJIOKA
- Dr Zbigniew WSZOLEK
- Dr Shozaburo YANAMOTO