DNA icon

Thrombocytopenia Absent Radius (TAR) Syndrome via the RBM8A Gene

Summary and Pricing

Test Method

Bi-Directional Sanger Sequencing
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
1721 RBM8A 81479 81479 $540 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
1721RBM8A81479 81479 $540 Order Options and Pricing

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

Turnaround Time

12 days on average for standard orders or 8 days 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.

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Siwu Peng, PhD

Clinical Features and Genetics

Clinical Features

Thrombocytopenia with Absent Radius Syndrome (TAR) (CTRUS) is characterized by thrombocytopenia, bleeding diathesis, and absence of the radius with preservation of the thumb. Bleeding episodes associated with TAR tend to be moderate to severe after birth, but tend to diminish in frequency and severity over time. Skeletal abnormalities may extend to the absence of upper limbs and to the hips and knees (Greenhalgh et al. 2002). Absent radius combined with a blood phenotype is also a characteristic of Fanconi anemia (FA); FA can be distinguished from TAR by absence of the thumb in addition to the absent radius (Tischkowitz and Hodgson 2003; Dokal 2000). Other symptoms of TAR may include intolerance to cow’s milk, renal anomalies, and cardiac anomalies (Greenhalgh et al. 2002).

Genetics

TAR does not appear to follow a typical autosomal dominant or recessive pattern of inheritance. Rather, the vast majority of patients with TAR have a compound inheritance that includes a null allele and a low frequency variant in the RBM8A gene. Most patients with TAR harbor a large deletion of chromosome 1q21.1, which includes the RBM8A gene (Klopocki et al. 2007; Papoulidis et al. 2014). Other reported null variants associated with TAR include a small insertion (c.207_208insAGCG) resulting in premature protein termination (p.Val70Serfs*3) (Albers et al. 2012) and a nonsense variant c.487C>T (p.Arg163*) (Albers et al. 2012). Paring one of these null alleles with one of two noncoding variants on the other allele, either c.-21G>A or c.67+32G>C, is strongly associated with disease; this combination of variants was found in 53 of 55 cases in one report with 51 cases having a large 1q21.1 deletion (Albers et al. 2012). This test includes sequencing of the coding regions of the RBM8A gene and sequencing for the c.-21G>A and c.67+32G>C variants. Due to the high frequency of the large 1q21.1 deletion in patients with TAR, we also offer a deletion test, and a comprehensive TAR test with sequencing and deletion testing performed concurrently.

Clinical Sensitivity - Sanger Sequencing

In one study, 51 of 55 cases, or approximately 93% of TAR syndrome patients, were found to harbor one of two "functional polymorphisms" in the RBM8A gene (either c.-21G>A or c.67+32G>C) in combination with a large 1q21.1 deletion that includes the RBM8A gene (Albers et al 2012). An additional 2 patients were found to harbor one of the two functional polymorphisms in combination with a null allele other than the large 1q21.1 deletion.   

Testing Strategy

For this sequencing test, the full coding region, plus ~10 bp of non-coding DNA flanking each exon, are sequenced for the RBM8A gene using Sanger sequencing. We also included in this test sequencing for the c.-21G>A and c.67+32G>C variants detailed above. This test provides 100% coverage of the RBM8A gene. We will also sequence any single exon (Test #100) or pair of exons (Test #200) in family members of patients with known mutations or to confirm research results.

Testing for sequence variants in the RBM8A gene and for the large 1q21.1 deletion is recommended if the index of suspicion for TAR is high.

Indications for Test

Patients with absent radius with or without thrombocytopenia and patients with absent radius with other sympotoms such as intolerance to cow's milk, cardiac anomalies, and renal anomalies.

Gene

Official Gene Symbol OMIM ID
RBM8A 605313
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Thrombocytopenia-Absent Radius Syndrome AR 274000

Related Tests

Name
Bernard-Soulier Syndrome via the GP1BA Gene
Bernard-Soulier Syndrome via the GP1BB Gene
Bernard-Soulier Syndrome via the GP9 Gene
Otopalatodigital Spectrum Disorders, Periventricular Nodular Heterotopia and Cardiac Valvular Dystrophy via the FLNA Gene
Thrombocytopenia Absent Radius (TAR) Syndrome via the RBM8A 1q21.1 Deletion
Thrombocytopenia Absent Radius (TAR) Syndrome via the RBM8A Gene - Sequencing and 1q21.1 Deletion
Thrombocytopenia with Predisposition to Acute Myelogenous Leukemia via the RUNX1 Gene
Wiskott-Aldrich Syndrome, X-linked Thrombocytopenia, and X-linked Congenital Neutropenia, via the WAS Gene

Citations

  • Albers C.A. et al. 2012. Nature Genetics. 44: 435-9, S1-2. PubMed ID: 22366785
  • Dokal I. 2000. The genetics of Fanconi’s anaemia. Baillieres Best Pract. Res. Clin. Haematol. 13: 407–425. PubMed ID: 11030042
  • Greenhalgh K.L. et al. 2002. Journal of Medical Genetics. 39: 876-81. PubMed ID: 12471199
  • Klopocki E. et al. 2007. American Journal of Human Genetics. 80: 232-40. PubMed ID: 17236129
  • Papoulidis I. et al. 2014. Molecular Medicine Reports. 9: 163-5. PubMed ID: 24220582
  • Tischkowitz M.D., Hodgson S.V. 2003. Journal of Medical Genetics. 40: 1-10. PubMed ID: 12525534

Ordering/Specimens

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


Specimen Types

Specimen Requirements and Shipping Details

loading Loading... ×

ORDER OPTIONS

View Ordering Instructions

1) Select Test Method (Backbone)


1) Select Test Type


2) Select Additional Test Options

STAT and Prenatal Test Options are not available with Patient Plus.

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
Total Price: $
×
Copy Text to Clipboard
×