BLOOM'S SYNDROME

DNA ANALYSIS

Gene Mutation in the Ashkenazi Jewish Population
Bloom's syndrome is an autosomal recessive disorder characterized clinically by a small size and typical facial appearance, and cytogenetically by an increased rate of chromosome breakage and sister chromatid exchange. The genomic instability in Bloom's syndrome renders patients at a much higher risk for developing multiple types of cancers. This rare disease has a significantly higher incidence in the Ashkenazi Jewish population, wherein the carrier frequency was estimated at approximately 1 in 104. The Bloom's syndrome gene BLM on chromosome 15q26.1 encodes a DNA helicase. While multiple BLM mutations have been identified, a specific mutation was found to be homozygous in Ashkenazi Jewish Bloom's syndrome patients. This BLM ^Ash mutation consists of a 6 base deletion and 7 base insertion at nucleotide 2281 of the BLM gene, which can be detected by a PCR-based diagnostic test. The Baylor DNA Diagnostic laboratory is offering diagnostic testing for the Bloom's syndrome BLM ^Ash mutation specific for the Ashkenazi Jewish population.

Reasons For Referral:

Diagnostic testing for Ashenazi Jewish individuals with a diagnosis or possible diagnosis of Bloom's syndrome, or a positive family history of Bloom's syndrome.

Testing Methodology:

PCR amplification of BLM gene sequences surrounding the blm^Ash mutation at nucleotide 2281, and detection of the wild type and 2281del6ins7 mutation by allele-specific oligonucleotide (ASO) hybridization.