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Disease Profile

Spinocerebellar ataxia 18

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

G11.8

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)

SCA18; Spinocerebellar ataxia type 18; Sensorimotor neuropathy with ataxia autosomal dominant;

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: 98771

Definition
Spinocerebellar ataxia type 18 (SCA18) is a very rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term). It is characterized by sensory neuropathy and cerebellar ataxia.

Epidemiology
Prevalence is unknown. Only 26 cases in a 5-generation American family of Irish ancestry have been reported to date.

Clinical description
Onset is in the 2nd and 3rd decades of life with symptomatic onset ranging from 13 to 27 years. Patients initially present with axonal sensory neuropathy, while cerebellar ataxia and motor neuron dysfunction develop later.

Etiology
SCA18 has been linked to chromosome 7q22-q23 but the responsible gene mutation has not yet been identified. Both SCA3 and SCA4 are also associated with a peripheral neuropathy and should be taken into account in the differential diagnosis.

Prognosis
Prognosis is unclear. However, mean disease duration from age at onset of illness to age at last examination is about 24 years in the reported cases.

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
Areflexia
Absent tendon reflexes
0001284
Gait ataxia
Inability to coordinate movements when walking
0002066
Muscle weakness
Muscular weakness
0001324
Sensory impairment
0003474
30%-79% of people have these symptoms
Dysarthria
Difficulty articulating speech
0001260
Dysmetria
Lack of coordination of movement
0001310
Hearing impairment
Deafness
Hearing defect

[ more ]

0000365
Hyporeflexia of lower limbs
0002600
Lower limb hyperreflexia
Overactive lower leg reflex
0002395
Muscle fibrillation
0010546
Pes cavus
High-arched foot
0001761
Sensorimotor neuropathy
Nerve damage causing decreased feeling and movement
0007141
5%-29% of people have these symptoms
Cerebellar atrophy
Degeneration of cerebellum
0001272
Head tremor
0002346
Nystagmus
Involuntary, rapid, rhythmic eye movements
0000639
Peripheral axonal neuropathy
0003477
Skeletal muscle atrophy
Muscle degeneration
Muscle wasting

[ more ]

0003202
Titubation
0030187
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
0000006
Babinski sign
0003487
Dysdiadochokinesis
Difficulty performing quick and alternating movements
0002075
Hyporeflexia
Decreased reflex response
Decreased reflexes

[ more ]

0001265
Limb muscle weakness
Limb weakness
0003690
Onset
Age symptoms begin
0003674
Progressive gait ataxia
0007240
Sensory axonal neuropathy
0003390
Tremor
0001337

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

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