What having a BRCA1/2 gene mutation means

Receiving a positive test result for a BRCA1/2 gene mutation can be frightening but there are steps you can take to make it less daunting.

A positive test means that your chance of developing certain cancers will be higher than someone who does not have a genetic mutation in these genes. This table explains how your risk increases according to whether you have a BRCA1 or a BRCA2 gene mutation.

Chance of passing mutations on

Whether you’re a mother or a father, if you have a mutation in either BRCA1/2 gene then there is a 50% chance of passing the mutation on to your children. There are a few possible outcomes if both parents carry a BRCA1/2 gene mutation:

  • There is a 1 in 2 chance that your child will inherit a single BRCA1/2 gene mutation and a 1 in 4 chance that your child will not inherit any BRCA1/2 gene mutation at all. There is also a 1 in 4 chance that they will inherit both of the mutations.
  • If one parent has a mutation in their BRCA1 gene and the other in their BRCA2 gene and the child inherits both, then their risk of developing breast or ovarian cancer is that of a BRCA1 carrier.
  • If a child inherits the BRCA2 gene mutation from both sides, then they will have something called fanconi anaemia (also known as fanconi syndrome).  This disorder can lead to shorter growth, a smaller head and underdeveloped thumbs.  Fanconi anaemia also puts the child at higher risk of early childhood cancers, leukaemia and wilms tumours in the kidneys