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Spastic Paraplegia 20 (Troyer Syndrome) via the SPART (SPG20) 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
SPART 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
4539SPART81479 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


  • Greg Fischer, PhD

Clinical Features and Genetics

Clinical Features

Spastic paraplegia 20 (SPG20) is a rare neurological disorder also known as Troyer syndrome. It is characterized by dysarthria, distal muscle wasting, delayed cognitive development, and paraparesis (Proukakis et al. 2004). Other symptoms have also been observed, such as choreoathetosis, anxiety, and skeletal abnormalities of the hand. SPG20 occurs with high frequency in the Amish population (Cross and McKusick 1967; Bakowska et al. 2008). It was also reported in a large Omani kindred (Manzini et al. 2010; Tawamie et al. 2015) and one Turkish family (Alazami et al. 2015). The onset is usually in early childhood.


The inheritance pattern of SPG20 in reported families is consistent with autosomal recessive inheritance. Pathogenic variants in SPART (SPG20) are causative for the disease (Patel et al. 2002). SPART encodes the protein Spartin, whose function is not fully understood. Spartin is thought to have roles in protein folding and turnover in mitochondria and endoplasmic reticulum (Milewska et al. 2009). The N-terminal MIT domain in Spartin is important for the interaction with microtubule and trafficking molecules (Ciccarelli et al. 2003).To date, only 3 pathogenic variants have been identified in SPART. In Amish patients with SPG20, a homozygous 1-bp deletion (c.1110delA) has been found (Patel et al. 2002; Bakowska et al. 2008). Manzini et al. (2010) identified a homozygous 2-bp deletion (c.364_365delAT) in an Omani kindred. Alazami et al. (2015) identified a homozygous 1-bp duplication (c.1450dupA) in a Turkish family.

Clinical Sensitivity - Sequencing with CNV PGxome

It is difficult to estimate the clinical sensitivity of this test due to the lack of large cohort studies. All the pathogenic variants identified to date are detectable by this test.

Testing Strategy

This test provides full coverage of all coding exons of the SPART gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other 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).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

Individuals with symptoms consistent with a complex form of autosomal recessive spastic paraplegia, and family members of patients who have known SPART variants are candidates for this test. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in SPART.


Official Gene Symbol OMIM ID
SPART 607111
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Troyer Syndrome AR 275900


  • Alazami A.M. et al. 2015. Cell Reports. 10: 148-61. PubMed ID: 25558065
  • Bakowska J.C. et al. 2008. Archives of Neurology. 65: 520-4. PubMed ID: 18413476
  • Ciccarelli F.D. et al. 2003. Genomics. 81: 437-41. PubMed ID: 12676568
  • Cross H.E., McKusick V.A. 1967. Archives of Neurology. 16: 473-85. PubMed ID: 6022528
  • Manzini M.C. et al. 2010. Annals of Neurology. 67: 516-25. PubMed ID: 20437587
  • Milewska M. et al. 2009. Journal of Neurochemistry. 111: 1022-30. PubMed ID: 19765186
  • Patel H. et al. 2002. Nature Genetics. 31: 347-8. PubMed ID: 12134148
  • Proukakis C. et al. 2004. Journal of Neurology. 251: 1105-10. PubMed ID: 15372254
  • Tawamie H. et al. 2015. Molecular and Cellular Probes. 29: 315-8. PubMed ID: 26003402


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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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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