Two patients with germline mutations in both BRCA1 and BRCA2 discovered unintentionally: a case series and discussion of BRCA testing modalities

When a family is known to have a BRCA mutation, genetic testing for family members is typically limited to single site analysis of the known mutation. The exception to this is in Ashkenazi Jewish families, where testing for the three common Ashkenazi Jewish BRCA mutations is recommended. We report two cases, one without Ashkenazi Jewish ancestry and one with maternal Ashkenazi Jewish ancestry, who underwent Comprehensive BRACAnalysis testing despite known BRCA1 mutations in family members. Testing identified the BRCA1 mutation previously identified, and a second mutation in BRCA2. These cases raise the question of whether or not Single Site BRACAnalysis for a known familial BRCA mutation is always the appropriate test when testing an affected individual. The implications of missing a second mutation are discussed.