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Snyder-Robinson Syndrome, Spermine Synthase Deficiency via the SMS Gene

Summary and Pricing

Test Method

Sequencing and CNV Detection via NextGen Sequencing using PG-Select Capture Probes
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
SMS 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
9909SMS81479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Testing run on PG-select capture probes includes CNV analysis for the gene(s) on the panel but does not permit the optional add on of exome-wide CNV analysis. Any of the NGS platforms allow reflex to other clinically relevant genes, up to whole exome or whole genome sequencing depending upon the base platform selected for the initial test.

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

This test is also offered via a custom panel (click here) on our exome or genome backbone which permits the optional add on of exome-wide CNV or genome-wide SV analysis.

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


  • Li Fan, MD, PhD, FCCMG, FACMG

Clinical Features and Genetics

Clinical Features

Snyder-Robinson syndrome is characterized by mild to moderate X-linked intellectual disability, seizures, speech and gait abnormalities, marfanoid habitus, hypotonia and movement disorders, skeletal changes caused by osteoporosis, facial dysmorphism with a prominent lower lip, nasal voice, high, narrow or cleft palate, and long, thin fingers and toes (Cason et al. 2003; Becerra-Solano et al. 2009; Albert et al. 2015).

Affected males present reduced spermine synthase activity, correspondingly low levels of intracellular spermine in lymphocytes and fibroblasts, and elevated spermidine/spermine ratios (Cason et al. 2003). Carrier females are clinically normal (Becerra-Solano et al. 2009). Hypothetically, female carriers could develop symptoms due to skewed inactivation of X chromosome.


Snyder-Robinson syndrome is inherited in an X-linked recessive manner and is caused by pathogenic variants in the SMS gene encoding the polyamine biosynthetic enzyme spermine synthase. Spermine synthase is ubiquitously expressed and is responsible for the conversion of spermidine to spermine. Spermine, a polyamine, is known to be essential for normal cell growth, maintenance and survival (Cason et al. 2003; Kesler et al. 2009; Pegg and Michael 2010; Albert et al. 2015). The possible functions of spermine include resistance to reactive oxygen species and to other stress, ion channel regulation and bone development (Pegg 2014).

Pathogenic variants in SMS gene lead to greatly reduced spermine synthase activity and protein content. It was hypothesized that the tissue specificity of Snyder-Robinson syndrome arises from differential sensitivity to spermidine toxicity or spermine deficiency (Albert et al. 2015).

To date, pathogenic variants in SMS include only missense and one splice pathogenic variant. No large deletions or duplications have been reported in SMS (Becerra-Solano et al. 2009; Zhang et al 2013; Albert et al. 2015; Human Gene Mutation Database).

Clinical Sensitivity - Sequencing with CNV PG-Select

Clinical sensitivity is difficult to predict as only a few patients have been reported as case studies. Analytical sensitivity should be high as all reported pathogenic variants are detectable by DNA sequence analysis (Human Gene Mutation Database).

No large deletions or duplications have been reported in SMS (HGMD).

Testing Strategy

This test provides full coverage of all coding exons of the SMS gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.

Indications for Test

SMS sequencing test is recommended for suspected cases of Snyder-Robinson syndrome.


Official Gene Symbol OMIM ID
SMS 300105
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Snyder Robinson Syndrome XL 309583


  • Albert J.S. et al. 2015. Orphanet Journal of Rare Diseases. 10: 27. PubMed ID: 25888122
  • Becerra-Solano L.E. et al. 2009. American Journal of Medical Genetics. Part A. 149A: 328-35. PubMed ID: 19206178
  • Cason A.L. et al. 2003. European Journal of Human Genetics. 11: 937-44. PubMed ID: 14508504
  • Human Gene Mutation Database (Bio-base).
  • Kesler S.R. et al. 2009. Neurogenetics. 10: 299-305. PubMed ID: 19277733
  • Pegg A.E. 2014. Iubmb Life. 66: 8-18. PubMed ID: 24395705
  • Pegg A.E., Michael A.J. 2010. Cellular and Molecular Life Sciences. 67: 113-21. PubMed ID: 19859664
  • Zhang Z. et al. 2013. Human Molecular Genetics. 22: 3789-97. PubMed ID: 23696453


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

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View Ordering Instructions

1) Select Test Method (Platform)

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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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