Article Abstract:
The spectrum of 59 mutations in ATM found in ataxia-telangiectasia (A-T) patients in the British Isles has been reported. Of 51 mutations found in native British Isles families studied, 2 of 11 founder mutations brought a milder clinical phenotype relative to cerebellar degeneration and cellular features. In two A-T families, an ATM mutation that may be associated with a greater risk of breast cancer in both homozygotes and heterozygotes, even though there is a less severe A-T phenotype relative to the degree of cerebellar degeneration. The same mutation allows expression of full-length ATM protein at a level similar to that in people unaffected. Another 18 A-T people in 15 families have been studied. They developed, usually as children, lymphoma, lymphoma, preleukemic T-cell proliferation or Hodgkins and showed many types of ATM mutations. Also 25% of all A-T patients had in-fame deletions or missense mutation, many associated with expression of mutant ATM protein.
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Article Abstract:
Penetrances of BRCA1 1675delA and 1135insA are discussed as they relate to ovarian and breast cancer. Index cases for a study were found through a series of consecutive ovarian cancer and through a family cancer clinic and 20 of the patients had BRCA1 1675 delA, with 10 having 1135insA. RElatives were listed as having presence or absence of each of the cancers. No difference was found between the two mutations with respect to penetrance and expression. The disease began at age 30 and by age 50 48% of those with the mutation had one or both cancers with more ovarian than breast cancers recorded.
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Article Abstract:
Genetic heterogeneity and penetrance analysis has been carried out for the BRCA1 and BRCA2 genes in 237 breast cancer families. In an estimated 52% of the families the disease was linked to BRCA1, and in 32% of the families it was linked to BRCA2. In 16% it was linked to neither gene. It would appear that other predisposing genes exist. In the breast-ovarian cancer families 81% were linked to BRCA1 and 14% to BRCA2. Families included in the study were chosen without considering cancers other than breast cancer. Each had at least four cases of breast cancer.
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