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Test Catalog

Test ID: BLM    
Bloom Syndrome, Mutation Analysis, 2281del6/ins7

Useful For Suggests clinical disorders or settings where the test may be helpful

Carrier screening for individuals of Ashkenazi Jewish ancestry


Confirmation of suspected clinical diagnosis of Bloom syndrome in individuals of Ashkenazi Jewish ancestry


Prenatal diagnosis for at-risk pregnancies

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Bloom syndrome is characterized by short stature, sun sensitivity, susceptibility to infections, and a predisposition to cancer. Mutations in the BLM gene lead to genetic instability (increased chromosomal breakage and sister chromatid exchange) and cause the clinical manifestations of the syndrome. The protein encoded by the BLM gene is a helicase involved in maintaining DNA integrity. The carrier rate in the Ashkenazi Jewish population is 1/107. There is a common mutation in the Ashkenazi Jewish population: 2281delATCTGAins TAGATTC (2281del6/ins7). The carrier detection rate for this mutation is greater than 99%.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is not recommended as a first tier test to diagnose Bloom syndrome in individuals of non-Ashkenazi Jewish descent. In the non-Ashkenazi Jewish population, the recommended test is SCE / Chromosome Analysis, Sister Chromatid Exchange (SCE) for Bloom Syndrome, Blood.


This assay will not detect all of the mutations that cause Bloom syndrome. Therefore, the absence of a detectable mutation(s) does not rule out the possibility that an individual is a carrier of or affected with this disease.


Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.


Rare polymorphisms exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.


In rare cases, DNA alterations of undetermined significance may be identified.


A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Gross SJ, Pletcher BA, Monaghan KG: Carrier screening in individuals of Ashkenazi Jewish descent. Genet Med 2008 Jan;10(1):54-6

2. Hickson ID: RecQ helicases: Caretakers of the genome. Nat Rev Cancer 2003;3(3):169-178

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test