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Disease Profile

Spinocerebellar ataxia 31

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.



US Estimated


Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

SCA31; Spinocerebellar ataxia type 31; Spinocerebellar ataxia 16q22-linked


Congenital and Genetic Diseases; Nervous System Diseases


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 217012

An autosomal dominant cerebellar ataxia type III that is characterized by the late-onset of ataxia, dysarthria and horizontal gaze nystagmus, and that is occasionally accompanied by pyramidal signs, tremor, decreased vibration sense and hearing difficulties.

Spinocerebellar ataxia type 31 (SCA31) is the third most common form of ADCA 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, hearing difficulties, and blepharospasm

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

Diagnostic methods
Diagnosis is based on the characteristic clinical findings and molecular genetic testing. As the manifestations of SCA31 are not specific, diagnosis is only confirmed with the finding of a mutation in the BEAN1 gene

Differential diagnosis
Differential diagnosis includes other types of ADCA.

Genetic counseling
SCA31 is inherited autosomal dominantly with incomplete penetrance and genetic counseling is possible. Genetic counseling should be proposed to individuals having the disease-causing mutation informing them that there is 50% risk of passing the mutation to offspring.

Management and treatment
There is no cure for SCA31 and treatment is supportive. Physical therapy, as well as the use of canes and walkers, should be offered in order to maximize strength and maintain activity. Wheelchairs are eventually necessary. Speech therapy and communication devices may be useful to those with dysarthria. Dysphagia should be monitored to decrease the risk of aspiration pneumonia. In those with vertigo, vestibular suppressants may be beneficial. Annual neurological examinations are recommended to monitor disease progression.

Disease progression is very slow. Life expectancy is not reduced but the quality of life can be significantly affected. According to recent reports, patients can become wheelchair bound at age of 79 years, and died at age of 89 years.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Cerebellar atrophy
Degeneration of cerebellum
Difficulty articulating speech
Gait ataxia
Inability to coordinate movements when walking
30%-79% of people have these symptoms
Gaze-evoked horizontal nystagmus
Decreased reflex response
Decreased reflexes

[ more ]

Late onset
Involuntary, rapid, rhythmic eye movements
5%-29% of people have these symptoms
Hearing impairment
Hearing defect

[ more ]

Hyperactive deep tendon reflexes
Impaired vibratory sensation
Decreased vibration sense
Decreased vibratory sense
Diminished vibratory sense
Impaired vibratory sense

[ more ]

Sensorineural hearing impairment
Involuntary muscle stiffness, contraction, or spasm
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
Limb ataxia


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
  • Spinocerebellar Ataxia: Making an Informed Choice about Genetic Testing is a booklet providing information about spinocerebellar ataxia and is available as a PDF document on the University of Washington Medical Center Web site. Click on the title above to view this resource.


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Spinocerebellar ataxia 31. Click on the link to view a sample search on this topic.