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Spastic Paraplegia 28 via the DDHD1 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
DDHD1 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
4893DDHD181479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information.

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).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

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 28 (SPG28) is a type of hereditary spastic paraplegia (HSP) characterized by early-onset, slow and progressive weakness and spasticity of the lower limbs. A few cases with mild upper limb involvement have also been reported (Bouslam et al. 2005; Liguori et al. 2014; Mignarri et al. 2016; Miura et al. 2016). Some patients with SPG28 may also show distal sensory loss, axonal neuropathy and cerebellar eye movement disturbances (Bouslam et al. 2005; Tesson et al. 2012). Severity of symptoms and rate of progression are quite variable.


The transmission of disease in the families with SPG28 is consistent with autosomal recessive inheritance. Bouslam et al. (2005) mapped this disease to DDHD1 (DDHD-domain-containing 1), which belongs to the intracellular phospholipase A1 gene family and encodes phosphatidic acid-preferring phospholipase A1 (PA-PLA1). Following cell activation, phosphatidic acid is released and functions as a second messenger in several signaling pathways. PA-PLA1 is a lipase that catalyzes degradation of phosphatidic acid and attenuates cell activation (Higgs et al. 1998). PA-PLA1 is involved in the maintenance of the Golgi and ER structure, and regulation of mitochondrial dynamics. Pathogenic variants in DDHD1 may cause mitochondrial dysfunctions that result from the accumulation of phosphatidic acid (Higgs et al. 1998; Nakajima et al. 2002). To date, nonsense, splice, and small deletions/duplications have been identified in DDHD1 (Human Gene Mutation Database).

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 reported to date in DDHD1 are detectable by sequencing.

Testing Strategy

This test provides full coverage of all coding exons of the DDHD1 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 autosomal recessive spastic paraplegia, and family members of patients who have known DDHD1 variants are candidates for this test. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in DDHD1.


Official Gene Symbol OMIM ID
DDHD1 614603
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Spastic Paraplegia 28 AR 609340


  • Bouslam N. et al. 2005. Annals of Neurology. 57: 567-71. PubMed ID: 15786464
  • Higgs H.N. et al. 1998. The Journal of Biological Chemistry. 273: 5468-77. PubMed ID: 9488669
  • Human Gene Mutation Database (Bio-base).
  • Liguori R. et al. 2014. Journal of Neurology. 261: 1789-93. PubMed ID: 24989667
  • Mignarri A. et al. 2016. Journal of the Neurological Sciences. 362: 287-91. PubMed ID: 26944165
  • Miura S. et al. 2016. European Journal of Medical Genetics. 59: 413-6. PubMed ID: 27216551
  • Nakajima K. et al. 2002. The Journal of Biological Chemistry. 277: 11329-35. PubMed ID: 11788596
  • Tesson C. et al. 2012. American Journal of Human Genetics. 91: 1051-64. PubMed ID: 23176821


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

No Additional Test Options are available for this test.

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