New tool puts reproductive risk for BRCA carriers into perspective
Ever since the 1960s, the familial risk of breast and ovarian cancer has been recognised as the hereditary breast and ovarian cancer syndrome (HBOC). The genetic mutations responsible were shown to be located on chromosomes 17 and 13 and labelled BRCA1 and 2.
These mutations are dominant, meaning only one copy of the gene needs to be affected. More recently the effect of both genes bearing the mutation causing childhood disease and early onset cancers is becoming clearer. Many women carrying one of the BRCA mutations are unaware of this additional risk.
What this means is that if both a child’s mother and father carry a BRCA mutation, that child has a 75% risk of both genes being affected and a 100% risk of being a carrier.
The major risk to the child with dual BRCA mutation is a bone marrow disorder, Fanconi’s Anaemia. This is an incurable condition with a limited lifespan of about 30 years and much associated cancer.
Obviously, the risk of this happening is much greater in populations where there is a high BRCA mutation, such as Ashkenazi Jews and the Shetlanders. Advice about possible dual inheritance should form part of genetic counselling.
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