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Ashkenazi Jews and Genetic Mutations
Bloom’s syndrome (also referred to as BS, Bloom-Torre-Mackacek Syndrome, Levi’s Type Dwarfism, and Congenital Telangiectatic Erythema) is a rare genetic disease most commonly found among Ashkenazi Jews, with a carrier incidence rate of 1 in 100 individuals. A child with two carrier parents has a 1 in 4 chance of inheriting the disease. In other words it follows an autosomal recessive pattern of inheritance.
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Bloom's syndrome is caused by mutations in the BLM gene, a member of the DNA helicase family. These mutations prevent the BLM gene from producing a sufficient amount of protein. Because BLM protein is what maintains stability during the DNA replication process, an insufficient amount of this protein leads to errors (e.g., chromosomal breakages and rearrangements) in this process, resulting in a further increase in mutations. As a result, some geneticists classify Bloom’s syndrome as a chromosomal breakage syndrome.
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Characteristics of Bloom’s syndrome include the following: short stature; a butterfly shaped rash on the face due to increased photosensitivity; an increased susceptibility to infections (especially ear infections and recurrent pneumonia) due to immune deficiency; and unusual facial characteristics such as a small lower jaw, a long, narrow face, and unusually large ears and nose. Other characteristics include a high-pitched voice, dilated blood vessels appearing on the skin and in the eyes, hyper- and hypo-pigmentation, infertility in males due to an inability to produce sperm, and early menopause and reduced fertility in females. The most significant characteristic of Bloom’s syndrome is a significantly higher risk of cancer, including carcinomas, leukemias, and lymphomas. Those afflicted with Bloom’s syndrome are much more likely to develop cancer at a much earlier age relative to those in the general population. The average age of diagnosis being approximately 25 years old.
Additional health complications associated with Bloom’s syndrome include diabetes, learning disabilities, and chronic lung problems. A small number of individuals with this rare genetic disease have mental retardation. Bloom’s syndrome itself is not curable; the resulting illnesses can be managed and treated. However, many individuals with this genetic disorder die whilst in their teens or twenties.
This series describes the diseases tested for in the Ashkenazi Jewish Genetics Panel (AJGP).