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Disease Profile

Spinocerebellar ataxia 20

Prevalence
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.
<1 / 1 000 000

< 331

US Estimated

< 514

Europe Estimated

Age of onset

Adult

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ICD-10

G11.2

Inheritance

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

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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

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X-linked
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.

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

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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.

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Not applicable

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Other names (AKA)

SCA20; Spinocerebellar ataxia type 20

Categories

Congenital and Genetic Diseases; Nervous System Diseases

Summary

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

Orpha Number: 101110

Definition
Spinocerebellar ataxia type 20 (SCA20) is a very rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term). It is characterized by cerebellar dysarthria as the initial typical manifestation.

Epidemiology
Prevalence is unknown. Fewer than 20 cases in a 4-generation Australian family of Anglo-Celtic descent have been reported to date.

Clinical description
Age of symptomatic disease onset ranges from 19 to 64 years (mean age = 46.5 years). Most affected patients also exhibit palatal tremor and spasmodic dysphonia. Head computed tomography (CT) shows dentate calcifications.

Etiology
SCA20 has been linked to chromosome 11q12.2-11q12.3, overlapping with the locus for SCA5 (see this term), though clinical features differ. SCA5 belongs to type III ADCA (see this term) and represents a pure ataxia syndrome with on average earlier age of symptomatic disease onset ranging from 14 to 50 years. Since the causative gene is unknown, SCA20 and SCA5 may be proven genetically to be the same disorder.

Prognosis
Prognosis is relatively good. Most patients can walk with or without gait aids and many patients live to more than 60 years of age.

Visit the Orphanet disease page for more resources.

Symptoms

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:
HPO ID
80%-99% of people have these symptoms
Dysarthria
Difficulty articulating speech
0001260
30%-79% of people have these symptoms
Bradykinesia
Slow movements
Slowness of movements

[ more ]

0002067
Cerebellar atrophy
Degeneration of cerebellum
0001272
Cerebral calcification
Abnormal deposits of calcium in the brain
0002514
Hypermetric saccades
0007338
Laryngeal dystonia
0012049
5%-29% of people have these symptoms
Abnormal pyramidal sign
0007256
Downbeat nystagmus
0010545
Gait ataxia
Inability to coordinate movements when walking
0002066
Gaze-evoked nystagmus
0000640
Hyperreflexia
Increased reflexes
0001347
Isometric tremor
0030185
Upper limb postural tremor
0007351
Vertigo
Dizzy spell
0002321
1%-4% of people have these symptoms
Intention tremor
0002080
Percent of people who have these symptoms is not available through HPO
Adult onset
Symptoms begin in adulthood
0003581
Autosomal dominant inheritance
0000006
Dysphonia
Inability to produce voice sounds
0001618
High pitched voice
0001620
Limb ataxia
0002070
Nystagmus
Involuntary, rapid, rhythmic eye movements
0000639
Palatal myoclonus
0010530
Postural tremor
0002174
Slow progression
Signs and symptoms worsen slowly with time
0003677

Diagnosis

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

    Organizations

    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

        • 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. 
        • 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 20. Click on the link to view a sample search on this topic.