[Determination of a BRCA1 gene mutation in a family with hereditary breast cancer].

BACKGROUND Breast cancer is the main cause of death among women between 40 and 55 years old, in whom the hereditary cases are common. Therefore, the molecular diagnosis of germ line mutations involved in breast cancer susceptibility is relevant. BRCA1 and BRCA2 have been described as the two major genes involved in familial breast/ovarian cancer. We are performing a screening of BRCA1 and BRCA2 genes, in a group of 50 high risk Chilean families for breast/ovarian cancer. We have detected a mutation, 3936 C>T, that leads to a truncated protein, in two affected women from one of the families in study. AIM To report the results of the screening for 3936 C>T in healthy relatives of index women. MATERIAL AND METHODS The molecular diagnosis of this mutation was offered to the healthy members of this family, and 17 relatives accepted to be tested. The region of the BRCA1 gene that includes the 3936 C>T mutation, was analyzed through PCR amplification, digestion with restriction enzyme BstNI, and direct sequencing. RESULTS 3936 C>T DNA mutation was present in 8 relatives. CONCLUSIONS Considering the high risk of having a mutation in the BRCA1 gene, specially in pre-menopausal women, the molecular diagnosis, genetic and clinical counseling are highly relevant. In Chile the molecular diagnosis is still not widely applied.