National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Spinocerebellar ataxia 8


Other Names:
SCA8; Spinocerebellar ataxia type 8
Categories:
This disease is grouped under:
Spinocerebellar ataxia type 8 (SCA8) is an inherited neurodegenerative condition characterized by slowly progressive ataxia (problems with movement, balance, and coordination). This condition typically occurs in adulthood and usually progresses over decades. Common initial symptoms include dysarthria, slow speech, and trouble walking. Some affected individuals experience nystagmus and other abnormal eye movements. Life span is typically not shortened. This condition is inherited in an autosomal dominant manner, although not all individuals with abnormalities in the disease-causing gene will develop the disease (called reduced penetrance).[1][2]
Last updated: 1/2/2012

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.

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Medical Terms Other Names
Learn More:
HPO ID
30%-79% of people have these symptoms
Bradykinesia
Slow movements
Slowness of movements
[ more ] 		0002067
Cerebellar atrophy
Degeneration of cerebellum
0001272
Cerebellar vermis atrophy 0006855
Dystonia 0001332
Gait ataxia
Inability to coordinate movements when walking
0002066
Hyperreflexia
Increased reflexes
0001347
Impotence
Difficulty getting a full erection
Difficulty getting an erection
[ more ] 		0000802
Limb ataxia 0002070
Nystagmus
Involuntary, rapid, rhythmic eye movements
0000639
Postural instability
Balance impairment
0002172
Rigidity
Muscle rigidity
0002063
Spastic dysarthria 0002464
Unsteady gait
Unsteady walk
0002317
5%-29% of people have these symptoms
Aspiration 0002835
Depressivity
Depression
0000716
Dysphagia
Poor swallowing
Swallowing difficulties
Swallowing difficulty
[ more ] 		0002015
Facial grimacing 0000273
Hypoplasia of the pons 0012110
Impaired smooth pursuit 0007772
Impaired vibratory sensation
Decreased vibration sense
Decreased vibratory sense
Diminished vibratory sense
Impaired vibratory sense
[ more ] 		0002495
Sensory neuropathy
Damage to nerves that sense feeling
0000763
Urinary incontinence
Loss of bladder control
0000020
Percent of people who have these symptoms is not available through HPO
Abnormal pyramidal sign 0007256
Autosomal dominant inheritance 0000006
Dysarthria
Difficulty articulating speech
0001260
Dysmetric saccades
Uncoordinated eye movement
0000641
Incoordination
Difficulties in coordination
Incoordination of limb movements
Limb incoordination
[ more ] 		0002311
Morphological abnormality of the pyramidal tract 0002062
Peripheral neuropathy 0009830
Progressive cerebellar ataxia 0002073
Slow saccadic eye movements
Slow eye movements
0000514
Spasticity
Involuntary muscle stiffness, contraction, or spasm
0001257
Tremor 0001337
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Last updated: 7/1/2020
Spinocerebellar ataxia 8 (SCA8) is more genetically complex than other SCAs.[3] Typically, a genetic disorder is considered autosomal dominant if only one copy of the defective gene needs to be inherited in order to develop the disease, and autosomal recessive if two copies of the defective gene (one from each parent) are required to develop the disease. SCA8 is a dominant condition because only one copy of the causative gene needs to be inherited, but quite often, family histories give the impression that the condition is sporadic (appearing without a family history) or inherited in an autosomal recessive manner.[3]

Genes are made up of substances known as nucleotides (identified by letters) linked together in chains. In SCA8, a change (mutation) in the ATXN8OS gene results in extra copies of a series of nucleotides identified by the letters CTG (this is called a trinucleotide repeat expansion). The ATXN8OS gene is genetically "unstable" which means that the number of repeats may expand or contract when the gene is passed on. Therefore, there are several potential outcomes for families in which the unstable gene is present: when a parent is unaffected, the number of CTG repeats can expand to cause the disease in a child; when a parent is affected, the number of repeats might contract (decrease) so that the child does not have the disease; an affected parent may have an affected child; or an unaffected parent may have an unaffected child. This unique aspect of SCA8 helps to explain why some family members can inherit the abnormal gene but not develop the disease, and why some family members develop the disease when neither parent is affected.[3][2]
Last updated: 1/2/2012

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.

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

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

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources

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

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • 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. 
    The Online Mendelian Inheritance in Man (OMIM)
    The Online Mendelian Inheritance in Man (OMIM)
  • 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 8. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • I am receiving genetic testing for spinocerebellar ataxia type 8 in approximately a week. How do I know if I inherited it from my mom or dad? Both are deceased and there is no family history of the disease. I am 62 yrs. old and first noticed symptoms approximately 4 years ago. See answer


  1. Ikeda Y, Dalton JC, Day JW & Ranum LPW. Spinocerebellar Ataxia Type 8. GeneReviews. February 2007; http://www.ncbi.nlm.nih.gov/books/NBK1268/. Accessed 10/12/2011.
  2. Yoshio Ikeda, Joline C Dalton, John W Day, Laura PW Ranum. Spinocerebellar Ataxia Type 8. GeneReviews. February 7, 2007; http://www.ncbi.nlm.nih.gov/books/NBK1268/. Accessed 1/2/2011.
  3. Spinocerebellar Ataxia Type 8 (SCA8). National Ataxia Foundation. http://www.ataxia.org/pdf/NAF%20Web%20Content%20Publication%20SCA8.pdf. Accessed 1/2/2011.