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Bloom's Syndrome via the BLM 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
BLM 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
3089BLM81479 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


  • Yuan Xue, PhD

Clinical Features and Genetics

Clinical Features

Bloom’s syndrome (BS; OMIM 210900) was first described in 1954 as a “congenital” skin disorder in “dwarfs” (Bloom Am J Dis Child 88:754-758, 1954). While patients were found to have additional clinical features, such as immune deficiencies and a propensity for cancer (German et al. Science 148:506-507, 1965; German Am J Hum Genet 21-196-227, 1969), sun-sensitive facial lesions, low birth weight and stunted growth remain the most consistent features of Bloom’s syndrome today. Symptoms of BS are related to increased mutability of proliferating somatic cells, particularly epithelial cells and lymphocytes. When grown in culture and viewed microscopically, cells of BS patients exhibit extensive “chromosome breakage”, including gaps and breaks, structural rearrangements, and telomeric associations (German and Crippa Ann Genet 9143-154, 1966). Chromosome breakage ultimately leads to excessive somatic recombination and high variant rates (Groden and German Hum Genet 90:360-367, 1992). About one-third of individuals with BS die by the age of 30 due to complications of cancer or from chronic lung disease as a result of immune deficiency (German Cancer Genet Cytogenet 93:100-106, 1997).


Bloom’s syndrome is an autosomal recessive disorder, caused by homozygous or compound heterozygous variants in the BLM gene (German et al. Hum Mutat 28:743-753, 2007); more than 60 unique variants have been identified. Most (60%) are single nucleotide changes leading to nonsense, missense, or splicing variants, while the remaining are small insertions or deletions (35%) or large deletions of multiple exons (5%). The BLM gene encodes a DNA helicase of the RecQ family. RecQ proteins are critical for maintaining the efficiency and integrity of DNA replication (Hickson Nat Rev Cancer 3:169-178, 2003); they resolve secondary structures ahead of replication forks, limit recombination to identical sequences, and assist in the replication and maintenance of telomeres (Bennett and Keck Crit Rev Biochem Mol Biol 39:79-97, 2004). In addition to these cellular functions, the BLM protein may also be important for the mismatch repair (MMR) pathway through its interaction with the MLH1 and MSH6 proteins (Langland et al. J Biol Chem 276:30031-30035, 2001; Pedrazzi et al. Biol Chem 384:1155-1164, 2003). Indeed, there is some evidence that heterozygous carriers of a BLM variant have an increased risk for colorectal cancer (Gruber et al. Science 297:2013, 2002), a disease most commonly associated with heterozygous variants in the MMR genes MLH1, MSH2 and MSH6.

Clinical Sensitivity - Sequencing with CNV PG-Select

In a retrospective study (German et al. Hum Mutat 28(8): 743-53, 2007), 87% of patients diagnosed with Bloom’s syndrome were reported to have two BLM variants. In 6% of the patients, only one variant was found for this recessive disease, indicating the second variant was not detectable by DNA sequencing methods.

Gross deletions of multiple exons account for approximately 5% of BLM cases.

Testing Strategy

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

Indications for Test

Candidates for this test are patients diagnosed with Bloom’s syndrome. This test is specifically designed for heritable germline variants and is not appropriate for the detection of somatic variants in tumor tissue. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in BLM.


Official Gene Symbol OMIM ID
BLM 604610
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Bloom Syndrome AR 210900


  • Bennett RJ, Keck JL. 2004. Structure and function of RecQ DNA helicases. Crit. Rev. Biochem. Mol. Biol. 39: 79-97. PubMed ID: 15217989
  • Bloom, D. 1954. Congenital telangiectatic erythema resembling lupus erythematosus in dwarfs; probably a syndrome entity. AMA Am J Dis Child 88(6): 754-8. PubMed ID: 13206391
  • German and Crippa Ann Genet 9143-154, 1966
  • German J, Sanz MM, Ciocci S, Ye TZ, Ellis NA. 2007. Syndrome-causing mutations of the BLM gene in persons in the Bloom’s Syndrome Registry. Human Mutation 28: 743–753. PubMed ID: 17407155
  • German, J. (1997). "Bloom's syndrome. XX. The first 100 cancers." Cancer Genet Cytogenet 93(1): 100-6. PubMed ID: 9062585
  • German, J. 1969. Bloom's syndrome. I. Genetical and clinical observations in the first twenty-seven patients. Am J Hum Genet 21(2): 196-227. PubMed ID: 5770175
  • German, J., et.al. 1965. Chromosomal Breakage in a Rare and Probably Genetically Determined Syndrome of Man. Science 148: 506-7. PubMed ID: 14263770
  • Groden, J., German, J. (1992). "Bloom's syndrome. XVIII. Hypermutability at a tandem-repeat locus." Hum Genet 90(4): 360-7. PubMed ID: 1483691
  • Gruber SB, Ellis NA, Scott KK, Almog R, Kolachana P, Bonner JD, Kirchhoff T, Tomsho LP, Nafa K, Pierce H, Low M, Satagopan J, et al. 2002. BLM heterozygosity and the risk of colorectal cancer. Science 297: 2013.. PubMed ID: 12242432
  • Hickson ID. 2003. RecQ helicases: caretakers of the genome. Nature Reviews Cancer 3: 169–178. PubMed ID: 12612652
  • Langland G. 2001. The Bloom’s Syndrome Protein (BLM) Interacts with MLH1 but Is Not Required for DNA Mismatch Repair. Journal of Biological Chemistry 276: 30031–30035. PubMed ID: 11325959
  • Pedrazzi G, Bachrati CZ, Selak N, Studer I, Petkovic M, Hickson ID, Jiricny J, Stagljar I. 2003. The Bloom’s syndrome helicase interacts directly with the human DNA mismatch repair protein hMSH6. Biol. Chem. 384: 1155–1164. PubMed ID: 12974384


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