Bloom syndrome is characterized by growth delay that begins during pregnancy and results in short stature, red sun-sensitive skin lesions on the face, and an increased risk of cancers with earlier than expected ages of onset. People with Bloom syndrome may also have recurrent pneumonia and ear infections, diabetes, and chronic pulmonary disease. Some individuals with Bloom syndrome have learning difficulties, although intelligence is typically within the normal range. Men with Bloom syndrome are infertile and women have reduced fertility and experience menopause at an earlier age.
Overall, Bloom syndrome confers a 150-300 times increased risk of cancer as compared to the general population, causing life expectancy to be shortened.
Approximately 1 in 104 people with Ashkenazi Jewish ancestry is a carrier of Bloom syndrome.
How Is Bloom Syndrome Inherited?
The cells in our body typically contain 46 chromosomes. Each chromosome is a package that holds hundreds of genes. These genes contain the all of the blueprints for our growth and development; they are the instructions that make us who we are. All of our chromosomes (and the genes that are located on these chromosomes) come in pairs. We inherit one chromosome of each pair from our mother and the other chromosome of the pair from our father. When there is a change in a gene (called a mutation) the instructions it contains are no longer correct and the gene cannot carry out its function.
Individuals with Bloom syndrome have two copies of a mutation, one copy inherited from each parent. Neither gene in the pair is working correctly, which causes the symptoms of the disease.
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A carrier of Bloom syndrome is a person who has a mutation in one gene of the pair. Carriers are unaffected with the disease because the properly working gene is able to compensate for the gene that contains the mutation.
When two parents are carriers of Bloom syndrome:
- there is a 1 in 4 (25%) chance of having a child with Bloom syndrome,
- there is a 1 in 2 (50%) chance of having a child who is an unaffected carrier like the parents,
- and, there is 1 in 4 (25%) chance of having a child who is unaffected and is not carrier.
When one parent is a carrier of Bloom syndrome and the other parent is not a carrier, they are not at increased risk to have a child with Bloom syndrome. Instead, there is a 1 in 2 (50%) chance of having a child with is an unaffected carrier like the one parent.
What This Test Tells You
This test tells whether you are a carrier of Bloom syndrome. It looks for the specific gene mutation (called blmAsh in the BLM gene) that accounts for 96.7% of mutations causing Bloom syndrome in people with Ashkenazi Jewish ancestry.
How Testing Works
Testing with DNA Direct is quick, convenient, and can be done in the privacy of your home. It can also be anonymous if you wish. How to order online and consult with our genetic experts: DNA Direct's Expert Services
References:
1. Shahrabani-Gargir L, Shomrat R, Yaron Y, Orr-Urtreger A, Groder J, Legum C. 1998. High frequency of a common Bloom syndrome Askenazi mutation among Jews of Polish origin. Genetic Testing 2:293-296.2. Li L, Eng C, Desnick RJ, German J, Ellis NA. 1998. Carrier frequency of the Bloom syndrome blmAsh mutation in the Ashkenazi Jewish population. Mol Genet Metab 64:286-290.
3. Roa BB, Savino CV, Richards CS. 1999. Ashkenazi Jewish population frequency of the Bloom syndrome gene 2281 delta 6ins7 mutation. Genet Test 3:219-221.
