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Autosomal Recessive Spinocerebellar Ataxia Type 4 (SCAR4) via the VPS13D Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
VPS13D 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
15131VPS13D81479 81479,81479 $990 Order Options and Pricing

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Erin Sybouts, PhD

Clinical Features and Genetics

Clinical Features

Spinocerebellar ataxia type 4 (SCAR4, also known as VPS13D movement disorder) is an extremely rare genetic movement disorder. The major features include ataxia, dystonia, chorea, and spasticity. Minor features can include developmental delay, mild intellectual disability, pyramidal signs, peripheral neuropathy, eye movement abnormalities, seizures, and abnormal brain MRI findings (Meijer. 2019. PubMed ID: 30789691).

Reported onset of symptoms is highly variable, ranging from infancy to adulthood. In general, features such as global developmental delay, hypotonia, chorea and mild intellectual disability were reported to have childhood onset, while development of progressive ataxia and dystonia were noted to have adult onset (Gauthier et al. 2018. PubMed ID: 29518281).

Advantages of testing include differential diagnosis from other ataxia-causing syndromes, molecular confirmation of diagnosis, and determining carrier status. In general, if the molecular cause of ataxia is not known (causative gene is not known), it is advisable to pursue larger panel testing or whole exome sequencing rather than a single gene test.


Many types of spinocerebellar ataxia have overlapping symptoms but differ in their genetic etiology. Autosomal recessive spinocerebellar ataxia 4 (SCAR4) is caused by biallelic pathogenic variants in the VPS13D gene.

The major pathogenic mechanism of VPS13D variants is loss of function variants, such as nonsense, frameshift, and splicing variants; however missense variants at highly conserved amino acid residues have also been reported (Gauthier et al. 2018. PubMed ID: 29518281; Seong et al. 2018. PubMed ID: 29604224; Koh et al. 2020. PubMed ID: 31876103). De novo variants have not been reported in SCAR4 patients to date nor have gross copy number variants (Meijer. 2019. PubMed ID: 30789691). Of note, partial duplication of VPS13D (exons 24-30) has been reported in the compound heterozygous state in one affected family (Gauthier et al. 2018. PubMed ID: 29518281).

Knockout of VPS13D homologs in flies and mice caused embryonic lethality in both organisms, indicating its importance in early development. In addition, both fly and human cells demonstrated abnormal mitochondrial structure and function with knockdown of Vps13D/VPS13D (Anding et al. 2018. PubMed ID: 29307555; Seong et al. 2018. PubMed ID: 29604224). Overall, VPS13D is considered an essential gene in human bone and soft tissue cell lines (Online Gene Essentiality, ogee.medgenius.info). VPS13D is ubiquitously expressed and is necessary for autophagy, mitochondrial size, and mitophagy (Anding et al. 2018. PubMed ID: 29307555; Seong et al. 2018. PubMed ID: 29604224).

Clinical Sensitivity - Sequencing with CNV PGxome

The clinical sensitivity of this test is difficult to estimate based on the phenotypic overlap with other disorders featuring ataxia, dystonia, chorea, or spasticity. Out of 664 patients with spastic paraplegia phenotypes, Koh and colleagues identified four patients with biallelic causative variants in VPS13D (Koh et al. 2020. PubMed ID: 31876103). Other disorders that would be beneficial to consider in the differential diagnosis of SCAR4 include other types of spinocerebellar ataxia, spastic ataxias, Leigh syndrome, and hereditary spastic paraplegia (Meijer. 2019. PubMed ID: 30789691).

Testing Strategy

This test is performed using Next-Generation Sequencing with additional Sanger sequencing as necessary. 

This test provides full coverage of all coding exons of the VPS13D gene plus 10 bases flanking noncoding DNA in all available transcripts in addition to non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as ≥20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

This test is performed using Next-Generation sequencing on our exome backbone. There is the option to reflex to whole exome sequencing (PGxome).

Indications for Test

Candidates for this test include individuals with features consistent with autosomal recessive spinocerebellar ataxia type 4 (SCAR4), such as dystonia, chorea, spasticity, or ataxia with or without developmental delays. Targeted testing is indicated for family members of patients who have a known pathogenic variant in VPS13D. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in VPS13D.


Official Gene Symbol OMIM ID
VPS13D 608877
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Spinocerebellar ataxia, autosomal recessive 4 AR 607317


  • Anding et al. 2018. PubMed ID: 29307555
  • Gauthier et al. 2018. PubMed ID: 29518281
  • Koh et al. 2020. PubMed ID: 31876103
  • Meijer. 2019. PubMed ID: 30789691
  • Online GEne Essentiality Database (OGEE).
  • Seong et al. 2018. PubMed ID: 29604224


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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View Ordering Instructions

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2) Select Additional Test Options

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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